{"id":59,"slug":"59-humanin-n-terminal-myristoylation-covalent-attachment-of-myristic-ac","title":"Humanin N-terminal myristoylation to enhance mitochondrial/membrane targeting for BAX antagonism","status":"FAILED","fold_verdict":"FAILED","discard_reason":null,"peptide":{"name":"Humanin","class":"LONGEVITY","sequence":"MAPRGFSCLLLLTSEIDLPVKRRA","modified_sequence":"Myr-MAPRGFSCLLLLTSEIDLPVKRRA","modification_description":"N-terminal myristoylation: covalent attachment of myristic acid (C14 saturated fatty acid) to the α-amine of Met-1 via amide bond, yielding Myr-MAPRGFSCLLLLTSEIDLPVKRRA"},"target":{"protein":"Apoptosis regulator BAX","uniprot_id":"Q07812","chembl_id":"CHEMBL2364","gene_symbol":"BAX"},"rationale":{"hypothesis":"We hypothesize that N-terminal myristoylation of Humanin will enrich the peptide at mitochondrial outer membranes — the site where BAX inserts and oligomerizes during apoptosis induction — and thereby increase the effective local concentration available for BAX groove engagement. Myristoyl groups are well-established membrane anchors (e.g., Src-family kinases, BID's tBID fragment) that partition lipidated proteins to lipid bilayers, and the BAX interaction is intrinsically a membrane-proximal event. Structurally, we expect the lipid to dock against a hydrophobic patch on BAX's α1-α2 region while the central Humanin helix (residues 5-15) engages the canonical groove.","rationale":"BAX activation occurs at the mitochondrial outer membrane, and native Humanin's BAX-inhibitory activity is concentration-limited intracellularly. Myristoylation is a validated strategy for membrane targeting (cf. tBID, MARCKS, Src) and has been used clinically to extend peptide PK without disrupting helical secondary structure when placed at flexible termini — Humanin's Met-1-Ala-2-Pro-3 N-terminus is disordered and tolerant of bulky N-caps. This diverges from the last 3 folds (Semax cyclization REFINED, Retatrutide lactam REFINED, Sermorelin hexenoyl+amidation DISCARDED) by switching focus to DELIVERY and category to Lipidation, neither of which appeared in folds #55-57. It also avoids repeating the prior Humanin disulfide (Fold #22) and S7A (Fold #37) strategies.","predicted_outcome":"Boltz-2/Chai-1 should predict the Humanin α-helix (residues 5-19) docking into the BAX hydrophobic groove (near α3-α4/α5-α6) with the myristoyl chain projecting toward a hydrophobic patch or solvent — pLDDT >0.65 in the helical core, with the lipid tail showing higher flexibility. A successful fold preserves the native BAX interface while showing the lipid does not sterically clash with BAX α1.","mechanism_class":null,"biohacker_use":null},"confidence":{"plddt":null,"ptm":null,"iptm":null,"chai_agreement":null,"chai1_gated_decision":"SKIPPED_LOW_CONFIDENCE","binding_probability":null,"binding_pic50":null,"predicted_binding_change":null},"profile":{"aggregation_propensity":0.312,"stability_score":0.366,"bbb_penetration_score":0.159,"half_life_estimate":"moderate-to-long (~1–6 hours)"},"narrative":{"tldr":"Fold #59 attempted to predict the structure of N-terminal myristoylated Humanin (Myr-MAPRGFSCLLLLTSEIDLPVKRRA) in complex with the apoptosis regulator BAX, targeting mitochondrial outer membrane enrichment as a mechanism to enhance BAX antagonism. The prediction failed at the technical level: Boltz-2 exited without producing a PDB file, and Chai-1 cross-validation was not run, leaving the complex entirely unevaluated by structural tools. Heuristic sequence-based profiling confirms the native Humanin hydrophobic hotspot at residues 7–20 but provides no information about lipid placement or BAX engagement. This is a tool-limit failure, not a biological verdict on the myristoylation strategy.","detailed_analysis":"Humanin (HN) is a 24-amino acid mitochondria-derived peptide (MDP) with one of the most thoroughly validated anti-apoptotic mechanisms in the longevity peptide space. Its core biology — direct binding to BAX, prevention of BAX conformational activation, and suppression of mitochondrial outer membrane permeabilization (MOMP) — is established across biochemical, cellular, and biophysical studies going back to Guo et al. 2003. The 2019 Morris et al. work added a structural dimension, showing HN and BAX co-assemble into fibers in solution, with BAX's membrane-targeting C-terminal helix required for the interaction. This body of literature makes BAX an unusually well-supported target for a longevity peptide, and HN one of the more mechanistically credible peptides in this lab's portfolio.\n\nThe hypothesis tested in Fold #59 was membrane targeting by lipidation: attaching myristic acid (C14 saturated fatty acid) to the α-amine of Met-1 via an amide bond to create Myr-MAPRGFSCLLLLTSEIDLPVKRRA. The rationale draws on the well-established role of myristoylation in directing proteins to membranes — Src-family kinases, BID/tBID, MARCKS — and the fact that BAX insertion and oligomerization is a mitochondrial outer membrane (MOM) event. If BAX inhibition is intrinsically membrane-proximate (as Morris et al. 2019 imply), then co-localizing HN to the MOM via a myristoyl anchor could increase effective local concentration and enhance BAX engagement kinetics.\n\nHowever, this hypothesis carries meaningful biological tension that the literature surfaces. Guo et al. 2003 showed that HN prevents BAX translocation to the MOM — meaning the key inhibitory event likely occurs in the cytosol, before membrane insertion. Locking HN to the MOM via myristoylation could theoretically cause it to arrive 'too late' in the BAX activation sequence. Morris et al.'s in vitro fiber data, generated without membranes, further suggests cytosolic HN-BAX engagement is real and substantial. Additionally, myristoylation alone is frequently insufficient for selective MOM targeting without a complementary electrostatic 'second signal', raising the risk of non-specific membrane partitioning across ER, plasma membrane, and nuclear envelope. The loss of BimEL antagonism (a cytosolic function of native HN, per Luciano et al. 2005) is an additional concern if membrane anchoring sequesters the peptide away from cytosolic BH3-only proteins.\n\nDespite these biological nuances, the fold did not reach a structural verdict — the failure is purely technical. Boltz-2 exited without producing a PDB file. The most likely cause is the non-standard chemical entity: myristoylation is a covalent lipid modification (myristic acid amide-bonded to the N-terminal amine) that falls outside the canonical amino acid alphabet and requires either explicit small-molecule parameterization or a CCD ligand definition that current AlphaFold-derived pipelines do not natively handle. This is the same class of tool-limit failure seen in Fold #44 (palmitoyl-γGlu-Lys lipidation on Epitalon, pLDDT 0.34, DISCARDED) and Fold #58 (PEG2-TAT chimera on Epitalon, FAILED), both involving non-standard chemical conjugates that stress current prediction infrastructure.\n\nHeuristic sequence-based analysis of the unmodified Humanin sequence confirms the expected hydrophobic character: aggregation propensity 0.31 with a hotspot at residues 7–20 consistent with the known amphipathic helix, stability score 0.37, and moderate-to-long predicted half-life (1–6 hours). These metrics describe the native peptide core only and say nothing about the myristoyl tail's membrane insertion geometry, its effect on BAX groove access, or whether the lipid sterically clashes with the α1-α2 region of BAX. No pLDDT, pTM, or ipTM values were generated.\n\nIn the context of this lab's Humanin series, Fold #59 is the third distinct modification strategy tested on this peptide. Fold #22 introduced a disulfide bridge (Cys-8/S14C, PROMISING, pLDDT 0.56) to pre-organize the central helix for BAX groove engagement — a structure-stabilization approach. Fold #37 tested S7A substitution to bias activity toward intracellular BAX inhibition (DISCARDED, pLDDT 0.62) — a receptor-selectivity approach. Fold #59 now tests lipid-mediated membrane delivery — a pharmacokinetic/localization approach. The three folds together map out the major strategic axes for HN optimization: structural pre-organization, target selectivity, and membrane targeting. The first two produced usable structural data (even if modest); this third produced none.\n\nThe failure here is a tool gap, not a scientific dead end. Myristoylated peptides are experimentally accessible — solid-phase synthesis with a myristoyl NHS ester or myristoyl-CoA enzymatic transfer are both routine — and the BAX interaction is measurable by ITC, SPR, or the liposome permeabilization assay formats used in the original Humanin literature. The membrane-targeting hypothesis is biologically coherent even if the structural data to evaluate it remains absent. Fold #59 should be understood as a staging ground for wet-lab work rather than a failed prediction.","executive_summary":"Fold #59 — Humanin myristoylation for MOM-targeted BAX antagonism — hit a hard tool limit: Boltz-2 produced no structure for the lipidated peptide. No structural verdict possible; wet-lab synthesis and ITC/SPR remain the only path forward.","tweet_draft":"DISTILLATION №59 — FAILED.\nHumanin, N-terminal myristoylation → BAX antagonism via MOM targeting.\nBoltz-2 couldn't model the lipid mod — tool limit, not biology.\npLDDT: none. No structure generated.\nHypothesis survives. Needs wet lab.\nalembic.bio","research_brief_markdown":"# DISTILLATION №59 — FAILED\n## Humanin N-terminal myristoylation for mitochondrial membrane targeting / BAX antagonism\n\n---\n\n## TLDR\n\nFold #59 was **DISCARDED due to a tool-limit failure**: Boltz-2 exited without producing a PDB file when presented with N-terminal myristoylated Humanin (Myr-MAPRGFSCLLLLTSEIDLPVKRRA) in complex with BAX. This is a **non-standard chemical entity failure** — the myristoyl amide bond to Met-1 falls outside the canonical amino acid alphabet that current AlphaFold-derived pipelines handle natively. No structural verdict on the hypothesis was reached. This is not a biological invalidation.\n\n---\n\n## What we tried\n\nHumanin (HN, MAPRGFSCLLLLTSEIDLPVKRRA) is a 24-amino acid mitochondria-derived peptide whose direct binding to BAX — preventing its conformational activation and translocation to the mitochondrial outer membrane (MOM) — is one of the most mechanistically supported anti-apoptotic interactions in the longevity peptide literature (Guo et al. 2003, Morris et al. 2019).\n\nThe hypothesis in Fold #59 was that covalent attachment of myristic acid (C14 saturated fatty acid) to the α-amine of Met-1 via an amide bond would enrich HN at the MOM — the precise site where BAX inserts and oligomerizes during apoptosis induction. The rationale draws on the validated membrane-targeting function of myristoylation in Src-family kinases, BID/tBID, and MARCKS, and on the Morris et al. 2019 finding that BAX's membrane-targeting C-terminal helix is required for HN-induced fiber formation, implying the HN–BAX interaction is intrinsically membrane-proximate. The expectation was that Boltz-2 would model the Humanin helix (residues 5–19) docking into the BAX hydrophobic groove with the myristoyl chain projecting toward a hydrophobic surface patch, yielding pLDDT >0.65 in the helical core.\n\nThis fold is the third in the lab's Humanin series, following Fold #22 (disulfide cyclization Cys-8/S14C → PROMISING, pLDDT 0.56) and Fold #37 (S7A substitution for receptor selectivity → DISCARDED, pLDDT 0.62). Those two folds addressed structural pre-organization and target selectivity, respectively. Fold #59 introduced a third strategic axis: **pharmacokinetic membrane delivery**.\n\n---\n\n## Why it was discarded\n\nBoltz-2 exited without generating a PDB file. Chai-1 cross-validation was not run. The primary cause is the **non-standard chemical entity**: N-terminal myristoylation is a covalent lipid modification that requires explicit small-molecule parameterization (e.g., a CCD ligand code, SMILES input, or modified residue definition) that current AlphaFold-derived folding pipelines do not handle within the standard amino acid alphabet. The myristoyl amide at Met-1 cannot be represented as a sequence character, and without a coordinate template or ligand definition, the predictor cannot place or score it.\n\nThis is the same class of failure seen in **Fold #44** (palmitoyl-γGlu-Lys lipidation on Epitalon, pLDDT 0.34, DISCARDED) and **Fold #58** (PEG2-TAT chimera on Epitalon, FAILED) — both involving non-peptidic conjugates that exceed current tool resolution. The pattern is consistent: lipid-modified and PEGylated peptides are a systematic blind spot for this generation of structure predictors.\n\nNo structural metrics were produced. Heuristic sequence analysis of the unmodified Humanin backbone yielded: aggregation propensity 0.31 (hotspot residues 7–20, consistent with the known amphipathic helix), stability score 0.37, BBB penetration 0.16, and a moderate-to-long estimated half-life (1–6 hours). These describe the native peptide core only and carry no information about myristoyl tail geometry, BAX groove compatibility, or lipid-mediated membrane partitioning.\n\n---\n\n## What this doesn't mean\n\n**FAILED is not \"disproved.\"** The myristoylation-mediated membrane targeting hypothesis for Humanin has not been evaluated — it has been rendered invisible by current tool limitations. The biological logic remains coherent: BAX engagement is a membrane-proximate event, myristoylation is a validated MOM-targeting strategy, and co-localizing HN with BAX at the site of insertion is a mechanistically grounded approach. There is also genuine biological tension in the hypothesis — Guo et al. 2003 showed HN prevents BAX *translocation* to the MOM, implying cytosolic inhibition is the primary mechanism, and membrane anchoring could theoretically arrive too late in the activation sequence. Morris et al.'s in vitro fiber data (generated without membranes) further supports cytosolic HN-BAX engagement as real and substantial. These are scientific questions worth adjudicating experimentally, not computational artifacts. The absence of a structural prediction says nothing about whether myristoyl-HN would bind BAX, partition to the MOM, or enhance anti-apoptotic activity in cells.\n\n---\n\n## What would answer the question\n\n- **Solid-phase synthesis + ITC or SPR**: Myristoyl-HN is synthetically accessible via N-terminal myristoyl NHS ester coupling. Isothermal titration calorimetry or surface plasmon resonance against recombinant BAX (with and without lipid vesicles to mimic MOM context) would directly measure binding affinity and determine whether the lipid disrupts or preserves the HN–BAX interface. The liposome permeabilization assay format used by Guo et al. 2003 and Morris et al. 2019 is the gold-standard functional readout.\n- **FEP/MD simulation with explicit lipid bilayer**: Free-energy perturbation or molecular dynamics in an explicit DOPC/CL MOM-mimetic bilayer, with the myristoyl chain pre-inserted, could model BAX groove accessibility and myristoyl anchor geometry in silico — bypassing the AlphaFold blind spot for non-standard chemistry.\n- **Cellular BAX translocation assay**: GFP-BAX translocation from cytosol to mitochondria in response to apoptotic stimulus (e.g., staurosporine), with and without myristoyl-HN pre-treatment, would directly test the functional hypothesis in a relevant cellular context.\n- **Alternative computational tools**: RosettaLigand, Glide, or AutoDock with explicit myristoyl parameterization could predict the lipid tail placement and BAX groove binding mode — providing the structural data that AlphaFold-based pipelines cannot currently generate for lipidated peptides.\n\n---\n\n## Raw metrics\n\n| Metric | Value |\n|---|---|\n| pLDDT | None (no structure generated) |\n| pTM | None |\n| ipTM | None |\n| Binder probability | None |\n| Chai-1 agreement | None (not run) |\n| Heuristic aggregation propensity | 0.31 (hotspot residues 7–20) |\n| Heuristic stability score | 0.37 |\n| Heuristic BBB penetration | 0.16 |\n| Heuristic half-life estimate | Moderate-to-long (~1–6 hours) |\n\n*Heuristic metrics are sequence-based estimates of the unmodified Humanin backbone only — not real wet-lab measurements, not reflective of the myristoyl modification, and not predictive of BAX binding.*","structural_caption":"No structure was generated. Boltz-2 exited without producing a PDB file, and Chai-1 cross-validation was disabled, leaving the myristoyl-Humanin / BAX complex prediction unevaluated. Heuristic sequence-based profiling indicates moderate hydrophobic character (aggregation 0.31, hotspot at residues 7–20) consistent with the native Humanin helix, but this provides no information about BAX engagement or lipid placement.","key_findings_summary":"Humanin (HN) is a 24-amino acid mitochondria-derived peptide (MDP) with well-established anti-apoptotic activity, originally discovered in surviving neurons of Alzheimer's disease patients. Its interaction with BAX is among the most mechanistically studied aspects of its biology. The seminal 2003 paper by Guo et al. (PMID:12732850) demonstrated directly that HN binds BAX protein, prevents BAX conformational activation, blocks BAX translocation from cytosol to mitochondrial outer membranes, and suppresses cytochrome c release in vitro. Critically, reducing HN expression via siRNA sensitized cells to BAX-mediated death, establishing a physiologically relevant interaction. The 2004 Niikura review (PMID:15655255) further confirmed that intracellularly overexpressed HN suppresses mitochondria-mediated apoptosis specifically by inhibiting BAX activity, providing in-cell validation of the biochemical findings.\n\nThe most structurally and mechanistically informative paper for the proposed hypothesis is Morris et al. 2019 (PMID:31690630), which used biophysical methods (light scattering, CD, fluorescence spectroscopy, negative-stain EM) to show that HN and BAX form co-fibers in vitro, that BAX undergoes secondary and tertiary structural rearrangements upon HN binding, and that the BAX C-terminal helix (which mediates membrane association) is important for this fibrillation process. Crucially, HN mutations that alter anti-apoptotic activity also altered fiber morphology, directly linking the HN–BAX interaction to HN's functional mechanism. This study does not resolve a precise binding groove on BAX or confirm the α1-α2 hydrophobic patch engagement proposed in the hypothesis, but it strongly supports a membrane-proximate and conformationally specific interaction. HN's anti-apoptotic repertoire extends beyond BAX: Luciano et al. 2005 (PMID:15661735) showed HN also binds and inhibits BimEL, a BH3-only protein upstream of BAX, through a direct interaction distinct from its BAX-binding function, and can suppress Bak oligomerization independently of BAX, indicating the peptide has multiple nodes of action within the intrinsic apoptosis pathway.\n\nWith respect to the myristoylation modification specifically, no paper in this literature set directly investigates N-terminal lipid modification of Humanin, nor any lipidated HN analog. The broader literature on HN covers analogs such as S14G-HN (HNG), a point mutant with enhanced potency, but the mechanism of potency enhancement is attributed to altered receptor/protein binding rather than membrane targeting. The hypothesis that myristoylation would enrich HN at the mitochondrial outer membrane (MOM) is mechanistically plausible given the known biology of myristoylated proteins (Src-family kinases, BID/tBID) and the established fact that BAX insertion and oligomerization occurs at the MOM. The Morris et al. finding that BAX's membrane-associating C-terminal helix is important for HN-induced fiber formation further supports the idea that the HN–BAX interaction is intrinsically membrane-proximate. However, myristoylation introduces risk of altering peptide secondary structure or steric access to the BAX binding interface, and whether the N-terminus of HN is tolerant of bulky hydrophobic modifications without loss of BAX-binding activity is not addressed in any retrieved paper.\n\nThe broader HN literature establishes cytoprotective roles across cardiovascular disease (PMID:34896254), reproduction (PMID:34626748), diabetes (PMID:35432758), aging/senescence (PMID:37106758), and neurodegeneration (PMID:34626746, PMID:15655255), consistent with a peptide whose core anti-apoptotic function protects many tissue types. The IGF-I regulatory axis (PMID:27082450) represents an extracellular signaling function of HN that is mechanistically separate from the intracellular BAX-inhibition pathway relevant to this hypothesis. One preprint (DOI:10.1101/2025.08.26.25334376) notes that a variant in MT-SHLP3 (a related MDP locus) associates with mortality in acute respiratory failure, tangentially supporting the pathophysiological relevance of this peptide family but not directly informing the BAX interaction or lipidation strategy."},"structured":{"known_activity":null,"known_binders":null,"candidate_variants":null,"domain_annotations":null,"literature_context":{"pubmed":[{"pmid":"34626748","title":"The role of humanin in the regulation of reproduction.","abstract":"Humanin, a mitochondria-derived peptide, has been found to exert variously protective function in many tissues, especially in the nervous tissues. However, relatively limited studies have focused on the role of humanin in the regulation of reproduction. Current observations indicate that humanin plays an important role in regulating the response of the cell to oxidative stress and apoptosis in ovaries and testes via the modulation of several signaling pathways, especially when the body is in an abnormal state. Even so, the detailed mechanism of humanin function needs to be explored urgently. In this passage, we demonstrate how humanin exerts its protective role in female and male reproduction and raise several questions that need further investigations. Given humanin's new frontier for the design of novel therapeutic approaches for male infertility, male contraception, female infertility, and glucose metabolism in polycystic ovary syndrome, it is worthy of further study on its protective effects and clinical applications in reproductive function.","authors":["Lei Hui","Rao Meng"],"year":2022,"journal":"Biochimica et biophysica acta. General subjects"},{"pmid":"37106758","title":"Humanin and Its Pathophysiological Roles in Aging: A Systematic Review.","abstract":"BACKGROUND: Senescence is a cellular aging process in all multicellular organisms. It is characterized by a decline in cellular functions and proliferation, resulting in increased cellular damage and death. These conditions play an essential role in aging and significantly contribute to the development of age-related complications. Humanin is a mitochondrial-derived peptide (MDP), encoded by mitochondrial DNA, playing a cytoprotective role to preserve mitochondrial function and cell viability under stressful and senescence conditions. For these reasons, humanin can be exploited in strategies aiming to counteract several processes involved in aging, including cardiovascular disease, neurodegeneration, and cancer. Relevance of these conditions to aging and disease: Senescence appears to be involved in the decay in organ and tissue function, it has also been related to the development of age-related diseases, such as cardiovascular conditions, cancer, and diabetes. In particular, senescent cells produce inflammatory cytokines and other pro-inflammatory molecules that can participate to the development of such diseases. Humanin, on the other hand, seems to contrast the development of such conditions, and it is also known to play a role in these diseases by promoting the death of damaged or malfunctioning cells and contributing to the inflammation often associated with them. Both senescence and humanin-related mechanisms are complex processes that have not been fully clarified yet. Further research is needed to thoroughly understand the role of such processes in aging and disease and identify potential interventions to target them in order to prevent or treat age-related conditions.\n\nOBJECTIVES: This systematic review aims to assess the potential mechanisms underlying the link connecting senescence, humanin, aging, and disease.","authors":["Coradduzza Donatella","Congiargiu Antonella","Chen Zhichao","Cruciani Sara","Zinellu Angelo","Carru Ciriaco","Medici Serenella"],"year":2023,"journal":"Biology"},{"pmid":"34626746","title":"Humanin and Alzheimer's disease: The beginning of a new field.","abstract":"BACKGROUND: Humanin (HN) is an endogenous peptide factor and known as a member of mitochondrial-derived peptides. We first found the gene encoding this novel 24-residue peptide in a brain of an Alzheimer's disease (AD) patient as an antagonizing factor against neuronal cell death induced by AD-associated insults.\n\nSCOPE OF REVIEW: This review presents an overview of HN actions in AD-related conditions among its wide range of action spectrum as well as a brief history of the discovery.\n\nMAJOR CONCLUSIONS: HN exhibits multiple intracellular and extracellular anti-cell death actions and antagonizes various AD-associated pathomechanisms including amyloid plaque accumulation.\n\nGENERAL SIGNIFICANCE: This review concisely reflects accumulated knowledge on HN since the discovery focusing on its functions related to AD pathogenesis and provides a perspective to its potential contribution in AD treatments.","authors":["Niikura Takako"],"year":2022,"journal":"Biochimica et biophysica acta. General subjects"},{"pmid":"27082450","title":"Humanin: Functional Interfaces with IGF-I.","abstract":"Humanin is the first newly discovered peptide encoded in the mitochondrial genome in over three decades. It is the first member of a novel class of mitochondrial derived peptides. This small, 24 amino acid peptide was initially discovered to have neuroprotective effects and subsequent experiments have shown that it is beneficial in a diverse number of disease models including stroke, cardiovascular disease, and cancer. Over a decade ago, our lab found that humanin bound IGFBP-3 and more recent studies have found it to decrease circulating IGF-I levels. In turn, IGF-I also seems to regulate humanin levels and in this review, we cover the known interaction between humanin and IGF-I. Although the exact mechanism for how humanin and IGF-I regulate each other still needs to be elucidated, it is clear that humanin is a new player in IGF-I signaling.","authors":["Xiao J","Kim S-J","Cohen P","Yen K"],"year":2016,"journal":"Growth hormone & IGF research : official journal of the Growth Hormone Research Society and the International IGF Research Society"},{"pmid":"34896254","title":"Cardio-protective role of Humanin in myocardial ischemia-reperfusion.","abstract":"Mitochondria-derived peptides (MDPs) are bioactive peptides encoded by and secreted from the mitochondria. To date, a few MDPs including humanin, MOTS-c and SHLP1-6, and their diverse biological functions have been identified. The first and most studied MDP is humanin, a 24-amino-acid poly peptide. It was first identified in 2001 in the surviving neurons of patient with Alzheimer's disease, and since then has been well characterized for its neuro-protective effect through inhibition of apoptosis. Over the past two decades, humanin has been reported to play critical roles in aging as well as multiple diseases including metabolic disorders, cardiovascular diseases, and autoimmune disease. Humanin has been shown to modulate multiple biological processes including autophagy, ER stress, cellular metabolism, oxidative stress, and inflammation. A role for humanin has been shown in a wide range of cardiovascular diseases, such as coronary heart disease, atherosclerosis, and myocardial fibrosis. In this minireview, we will summarize the literature demonstrating a role for humanin in cardio-protection following myocardial ischemia-reperfusion induced injury and the potential mechanisms that mediate it.","authors":["Gong Zhenwei","Goetzman Eric","Muzumdar Radhika H"],"year":2022,"journal":"Biochimica et biophysica acta. General subjects"},{"pmid":"33130077","title":"Humanin: A mitochondrial-derived peptide in the treatment of apoptosis-related diseases.","abstract":"Humanin (HN) is a small mitochondrial-derived cytoprotective polypeptide encoded by mtDNA. HN exhibits protective effects in several cell types, including leukocytes, germ cells, neurons, tissues against cellular stress conditions and apoptosis through regulating various signaling mechanisms, such as JAK/STAT pathway and interaction of BCL-2 family of protein. HN is an essential cytoprotective peptide in the human body that regulates mitochondrial functions under stress conditions. The present review aims to evaluate HN peptide's antiapoptotic activities as a potential therapeutic target in the treatment of cancer, diabetes mellitus, male infertility, bone-related diseases, cardiac diseases, and brain diseases. Based on in vitro and in vivo studies, HN significantly suppressed the apoptosis during the treatment of bone osteoporosis, cardiovascular diseases, diabetes mellitus, and neurodegenerative diseases. According to accumulated data, it is concluded that HN exerts the proapoptotic activity of TNF-α in cancer, which makes HN as a novel therapeutic agent in the treatment of cancer and suggested that along with HN, the development of another mitochondrial-derived peptide could be a viable therapeutic option against different oxidative stress and apoptosis-related diseases.","authors":["Hazafa Abu","Batool Ammara","Ahmad Saeed","Amjad Muhammad","Chaudhry Sundas Nasir","Asad Jamal","Ghuman Hasham Feroz","Khan Hafiza Madeeha","Naeem Muhammad","Ghani Usman"],"year":2021,"journal":"Life sciences"},{"pmid":"35432758","title":"Humanin and diabetes mellitus: A review of","abstract":"Humanin (HN) is a 24-amino acid mitochondrial-derived polypeptide with cyto-protective and anti-apoptotic effects that regulates the mitochondrial functions under stress conditions. Accumulating evidence suggests the role of HN against age-related diseases, such as Alzheimer's disease. The decline in insulin action is a metabolic feature of aging and thus, type 2 diabetes mellitus is considered an age-related disease, as well. It has been suggested that HN increases insulin sensitivity, improves the survival of pancreatic beta cells, and delays the onset of diabetes, actions that could be deployed in the treatment of diabetes. The aim of this review is to present the in vitro and in vivo studies that examined the role of HN in insulin resistance and diabetes and to discuss its newly emerging role as a therapeutic option against those conditions.","authors":["Boutari Chrysoula","Pappas Panagiotis D","Theodoridis Theodoros D","Vavilis Dimitrios"],"year":2022,"journal":"World journal of diabetes"},{"pmid":"15655255","title":"Humanin: after the discovery.","abstract":"Humanin (HN) is a novel neuroprotective factor that consists of 24 amino acid residues. HN suppresses neuronal cell death caused by Alzheimer's disease (AD)-specific insults, including both amyloid-beta (betaAbeta) peptides and familial AD-causative genes. Cerebrovascular smooth muscle cells are also protected from Abeta toxicity by HN, suggesting that HN affects both neuronal and non-neuronal cells when they are exposed to AD-related cytotoxicity. HN peptide exerts a neuroprotective effect through the cell surface via putative receptor(s). HN activates a cellular signaling cascade that intervenes (at least) in activation of c-Jun N-terminal kinase. The highly selective effect of HN on AD-relevant cell death indicates that HN is promising for AD therapy. Additionally, a recent study showed that intracellularly overexpressed HN suppressed mitochondria-mediated apoptosis by inhibiting Bax activity.","authors":["Niikura Takako","Chiba Tomohiro","Aiso Sadakazu","Matsuoka Masaaki","Nishimoto Ikuo"],"year":2004,"journal":"Molecular neurobiology"},{"pmid":"31690630","title":"Humanin induces conformational changes in the apoptosis regulator BAX and sequesters it into fibers, preventing mitochondrial outer-membrane permeabilization.","abstract":"The mitochondrial, or intrinsic, apoptosis pathway is regulated mainly by members of the B-cell lymphoma 2 (BCL-2) protein family. BCL-2-associated X apoptosis regulator (BAX) plays a pivotal role in the initiation of mitochondria-mediated apoptosis as one of the factors causing mitochondrial outer-membrane permeabilization (MOMP). Of current interest are endogenous BAX ligands that inhibit its MOMP activity. Mitochondrial-derived peptides (MDPs) are a recently identified class of mitochondrial retrograde signaling molecules and are reported to be potent apoptosis inhibitors. Among them, humanin (HN) has been shown to suppress apoptosis by inhibiting BAX translocation to the mitochondrial outer membrane, but the molecular mechanism of this interaction is unknown. Here, using recombinant protein expression, along with light-scattering, CD, and fluorescence spectroscopy, we report that HN and BAX can form fibers together in vitro Results from negative stain EM experiments suggest that BAX undergoes secondary and tertiary structural rearrangements and incorporates into the fibers, and that its membrane-associating C-terminal helix is important for the fibrillation process. Additionally, HN mutations known to alter its anti-apoptotic activity affect fiber morphology. Our findings reveal for the first time a potential mechanism by which BAX can be sequestered by fibril formation, which can prevent it from initiating MOMP and committing the cell to apoptosis.","authors":["Morris Daniel L","Kastner David W","Johnson Sabrina","Strub Marie-Paule","He Yi","Bleck Christopher K E","Lee Duck-Yeon","Tjandra Nico"],"year":2019,"journal":"The Journal of biological chemistry"},{"pmid":"12732850","title":"Humanin peptide suppresses apoptosis by interfering with Bax activation.","abstract":"Bax (Bcl2-associated X protein) is an apoptosis-inducing protein that participates in cell death during normal development and in various diseases. Bax resides in an inactive state in the cytosol of many cells. In response to death stimuli, Bax protein undergoes conformational changes that expose membrane-targeting domains, resulting in its translocation to mitochondrial membranes, where Bax inserts and causes release of cytochrome c and other apoptogenic proteins. It is unknown what controls conversion of Bax from the inactive to active conformation. Here we show that Bax interacts with humanin (HN), an anti-apoptotic peptide of 24 amino acids encoded in mammalian genomes. HN prevents the translocation of Bax from cytosol to mitochondria. Conversely, reducing HN expression by small interfering RNAs sensitizes cells to Bax and increases Bax translocation to membranes. HN peptides also block Bax association with isolated mitochondria, and suppress cytochrome c release in vitro. Notably, the mitochondrial genome contains an identical open reading frame, and the mitochondrial version of HN can also bind and suppress Bax. We speculate therefore that HN arose from mitochondria and transferred to the nuclear genome, providing a mechanism for protecting these organelles from Bax.","authors":["Guo Bin","Zhai Dayong","Cabezas Edelmira","Welsh Kate","Nouraini Shahrzad","Satterthwait Arnold C","Reed John C"],"year":2003,"journal":"Nature"},{"pmid":"15106598","title":"Unravelling the role of Humanin.","abstract":"Humanin (HN), a recently identified neuroprotective factor against Alzheimer's disease-related insults, has been reported to function as an anti cell-death factor through multiple mechanisms. One mechanism, revealed in a glioblastoma cell line, involves the apoptosis-inducing protein Bax. This, in addition to the fact that HN is produced in certain normal tissues, such as testis, implies a potential role of HN in oncogenesis. A second mechanism, in neuronal cells, is via a putative cell-surface receptor. It is through this mechanism that HN exhibits its neuroprotective activity.","authors":["Nishimoto Ikuo","Matsuoka Masaaki","niikura Takako"],"year":2004,"journal":"Trends in molecular medicine"},{"pmid":"15661735","title":"Cytoprotective peptide humanin binds and inhibits proapoptotic Bcl-2/Bax family protein BimEL.","abstract":"Humanin (HN) is a recently identified endogenous peptide that protects cells against cytotoxicity induced by various stimuli. Recently, we showed that HN binds to and inhibits Bax, a proapoptotic Bcl-2 family protein, suggesting a mechanism for HN action. In this study, we identified Bim, a Bcl-2 homology 3-only member of the Bcl-2/Bax family, as an additional HN target protein. Using in vitro protein binding, immunoprecipitation, and coimmunolocalization assays, we demonstrated that HN binds directly to the extra long isoform of Bim (BimEL) but not the long (BimL) or short (BimS) isoforms. HN also protects cells against apoptosis induced by BimEL but not BimL and BimS in gene transfection studies. In contrast, mutants of HN which failed to bind BimEL failed to protect from BimEL-induced cell death. Moreover, HN inhibited BimEL-induced release of SMAC and cytochrome c from mitochondria isolated from bax-/-cells, indicating that HN can suppress BimEL independently of its effect on Bax. Finally, we demonstrate that HN prevents BimEL-induced oligomerization of Bak using isolated mitochondria. Taken together, our results indicate that the inhibition of BimEL may contribute to the antiapoptotic properties of the HN peptide.","authors":["Luciano Frederic","Zhai Dayong","Zhu Xiuwen","Bailly-Maitre Beatrice","Ricci Jean-Ehrland","Satterthwait Arnold C","Reed John C"],"year":2005,"journal":"The Journal of biological chemistry"}],"biorxiv":[{"pmid":"","doi":"10.21203/rs.3.rs-9040130/v1","title":"Renoprotective Effect of S14G-Humanin on Renal Ischemia/Reperfusion Injury by Activation of STAT3 and ERK 1/2 Signal Transduction Pathways in Rats","abstract":"<title>Abstract</title>  <p>Renal ischemia/reperfusion (I/R) injury leads to acute tubular necrosis and renal failure, triggering pathological mechanisms including inflammation, reactive oxygen species generation, apoptosis, and mitochondrial dysfunction. The mitochondrial peptide Humanin (HN), known to possess anti-apoptotic and anti-inflammatory properties, has been shown to counteract oxidative stress and restore mitochondrial function. This study aimed to investigate the effects of HN on renal I/R injury. Sprague-Dawley male rats were divided into four groups (n = 48): 1.Sham, 2.I/R, 3.HN-Sham, 4.HN-I/R. In I/R groups, renal artery ligation was performed for 45 minutes followed by 24-hour reperfusion. Humanin G (HNG) (2 mg/kg, iv) was administered 10 minutes before reperfusion. Urine was collected during reperfusion, and the experiment was terminated by collecting blood and tissue samples. Blood urea nitrogen and serum creatinine levels were elevated in the I/R group and were not affected by HNG treatment. Glutathione levels as well as superoxide dismutase activities, which were diminished in the I/R group, were significantly restored following HNG administration. Myeloperoxidase activity and malondialdehyde levels were significantly decreased in HN-I/R group compared to the I/R group. ATP levels and mitochondrial Complex I activity were significantly increased in the HN-I/R group compared to I/R. The percentage of apoptotic cells, markedly increased in I/R, was significantly reduced in HN-I/R. STAT3 and ERK 1/2 phosphorylation also increased in HN-I/R rats compared to I/R animals. HNG exerts a protective effect against renal I/R injury by attenuating oxidative stress, inflammation, and apoptosis while enhancing antioxidant capacity and mitochondrial function, through STAT3 and/or ERK 1/2 activation.</p>","authors":["Abueid L","Torun AF","Golal E","Acar N","Basralı F."],"year":2026,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.20944/preprints202604.0328.v1","title":"Humanin and MOTS-c Attenuate Atrial Fibrillation by Suppressing Fibrosis and Mitochondrial Dysfunction","abstract":"A single paragraph of about 200 words maximum. For research articles, abstracts should give a pertinent overview of the work. We strongly encourage authors to use the following style of structured abstracts, but without headings: (1) Background: Place the question addressed in a broad context and highlight the purpose of the study; (2) Methods: briefly describe the main methods or treatments applied; (3) Results: summarize the article’s main findings; (4) Conclusions: indicate the main conclusions or interpretations. The abstract should be an objective representation of the article and it must not contain results that are not presented and substantiated in the main text and should not exaggerate the main conclusions.","authors":["Liao Y","Xu J","Jiao Y","Sun X","Gao M","Ding Y","Cai D","Shen Y","Zhou X","Han W."],"year":2026,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.1101/2025.08.26.25334376","title":"Serum mtDNA DAMP abundance, fragmentation and heteroplasmic variants associate with Acute Respiratory Failure outcome: A secondary analysis of study NCT00976833","abstract":"<h4>Background</h4>  Serum mitochondrial DNA (mtDNA) fragments act as proinflammatory damage-associated molecular patterns (DAMPs), and have been linked to outcomes in critical illness. However, their prognostic value remains uncertain, possibly due to confounding nuclear mitochondrial insertions (NUMTs) which obscure both quantitation and variant detection. <h4>Methods</h4>  Using a targeted deep sequencing and bioinformatics workflow, we created filtering strategies to minimize NUMT-related artifacts. To evaluate the method, we performed a secondary analysis of serum samples collected from  NCT00976833 , a study of acute respiratory failure patients. By modeling DNA insert size distributions, we excluded likely NUMT-derived DNA fragments based on their size, improving the accuracy of mtDNA DAMP fragmentomic analysis. To improve variant detection, we introduced a novel “read mismatch percentage” metric to identify NUMT-induced chimeric read pairs, enabling identification of mtDNA variants.  <h4>Results</h4>  Mean NUMT-depleted, but not raw, mtDNA insert size was lower in non-survivors. Short DNA inserts (<150 bp) displayed little NUMT contamination, and their abundance and size correlated with mortality more strongly than total mtDNA abundance. Sequence variants were called and some associated with survival and post-acute quality of life. Variant m.1,719G  > A, found in small humanin-like 3 (  MT-SHLP3 ), associated with survival. Other variants associated with overall poor outcome (non-survival or poor QoL). Two noncoding variants previously associated with low VO2 max and coronary artery disease (m.295C  > T and m.462C  > T) also associated with poor outcome in the present study. Two  MT-ND5 variants m.13,708G  > A (a missense variant previously implicated in kidney dysfunction) and m.12,612A  > G (a synonymous variant previously associated with coronary artery disease) also associated with poor overall outcome.  <h4>Conclusions</h4>  Our results addressed limitations of standard qPCR-based methods for the study of mtDNA DAMPs. Beyond addressing confounding NUMT, the method identified fragmentomic and variant associations overlooked by qPCR. Cell-free DNA fragmentomic and variant information are well-established biomarkers for cancer, and this method could facilitate similar patient-specific biomarkers in the context of critical illness. The method is composed of commercially available reagents and open source software, which could additionally promote adoption and reproducibility.","authors":["Daly GT","Hartsell EM","Pastukh VM","Roberts JT","Haastrup AI","Purcell LD","Mulekar MS","Files DC","Morris PE","Gillespie MN","Langley RJ."],"year":2025,"journal":"PPR","source":"PPR","preprint":true}],"preprints":[{"pmid":"","doi":"10.21203/rs.3.rs-9040130/v1","title":"Renoprotective Effect of S14G-Humanin on Renal Ischemia/Reperfusion Injury by Activation of STAT3 and ERK 1/2 Signal Transduction Pathways in Rats","abstract":"<title>Abstract</title>  <p>Renal ischemia/reperfusion (I/R) injury leads to acute tubular necrosis and renal failure, triggering pathological mechanisms including inflammation, reactive oxygen species generation, apoptosis, and mitochondrial dysfunction. The mitochondrial peptide Humanin (HN), known to possess anti-apoptotic and anti-inflammatory properties, has been shown to counteract oxidative stress and restore mitochondrial function. This study aimed to investigate the effects of HN on renal I/R injury. Sprague-Dawley male rats were divided into four groups (n = 48): 1.Sham, 2.I/R, 3.HN-Sham, 4.HN-I/R. In I/R groups, renal artery ligation was performed for 45 minutes followed by 24-hour reperfusion. Humanin G (HNG) (2 mg/kg, iv) was administered 10 minutes before reperfusion. Urine was collected during reperfusion, and the experiment was terminated by collecting blood and tissue samples. Blood urea nitrogen and serum creatinine levels were elevated in the I/R group and were not affected by HNG treatment. Glutathione levels as well as superoxide dismutase activities, which were diminished in the I/R group, were significantly restored following HNG administration. Myeloperoxidase activity and malondialdehyde levels were significantly decreased in HN-I/R group compared to the I/R group. ATP levels and mitochondrial Complex I activity were significantly increased in the HN-I/R group compared to I/R. The percentage of apoptotic cells, markedly increased in I/R, was significantly reduced in HN-I/R. STAT3 and ERK 1/2 phosphorylation also increased in HN-I/R rats compared to I/R animals. HNG exerts a protective effect against renal I/R injury by attenuating oxidative stress, inflammation, and apoptosis while enhancing antioxidant capacity and mitochondrial function, through STAT3 and/or ERK 1/2 activation.</p>","authors":["Abueid L","Torun AF","Golal E","Acar N","Basralı F."],"year":2026,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.20944/preprints202604.0328.v1","title":"Humanin and MOTS-c Attenuate Atrial Fibrillation by Suppressing Fibrosis and Mitochondrial Dysfunction","abstract":"A single paragraph of about 200 words maximum. For research articles, abstracts should give a pertinent overview of the work. We strongly encourage authors to use the following style of structured abstracts, but without headings: (1) Background: Place the question addressed in a broad context and highlight the purpose of the study; (2) Methods: briefly describe the main methods or treatments applied; (3) Results: summarize the article’s main findings; (4) Conclusions: indicate the main conclusions or interpretations. The abstract should be an objective representation of the article and it must not contain results that are not presented and substantiated in the main text and should not exaggerate the main conclusions.","authors":["Liao Y","Xu J","Jiao Y","Sun X","Gao M","Ding Y","Cai D","Shen Y","Zhou X","Han W."],"year":2026,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.1101/2025.08.26.25334376","title":"Serum mtDNA DAMP abundance, fragmentation and heteroplasmic variants associate with Acute Respiratory Failure outcome: A secondary analysis of study NCT00976833","abstract":"<h4>Background</h4>  Serum mitochondrial DNA (mtDNA) fragments act as proinflammatory damage-associated molecular patterns (DAMPs), and have been linked to outcomes in critical illness. However, their prognostic value remains uncertain, possibly due to confounding nuclear mitochondrial insertions (NUMTs) which obscure both quantitation and variant detection. <h4>Methods</h4>  Using a targeted deep sequencing and bioinformatics workflow, we created filtering strategies to minimize NUMT-related artifacts. To evaluate the method, we performed a secondary analysis of serum samples collected from  NCT00976833 , a study of acute respiratory failure patients. By modeling DNA insert size distributions, we excluded likely NUMT-derived DNA fragments based on their size, improving the accuracy of mtDNA DAMP fragmentomic analysis. To improve variant detection, we introduced a novel “read mismatch percentage” metric to identify NUMT-induced chimeric read pairs, enabling identification of mtDNA variants.  <h4>Results</h4>  Mean NUMT-depleted, but not raw, mtDNA insert size was lower in non-survivors. Short DNA inserts (<150 bp) displayed little NUMT contamination, and their abundance and size correlated with mortality more strongly than total mtDNA abundance. Sequence variants were called and some associated with survival and post-acute quality of life. Variant m.1,719G  > A, found in small humanin-like 3 (  MT-SHLP3 ), associated with survival. Other variants associated with overall poor outcome (non-survival or poor QoL). Two noncoding variants previously associated with low VO2 max and coronary artery disease (m.295C  > T and m.462C  > T) also associated with poor outcome in the present study. Two  MT-ND5 variants m.13,708G  > A (a missense variant previously implicated in kidney dysfunction) and m.12,612A  > G (a synonymous variant previously associated with coronary artery disease) also associated with poor overall outcome.  <h4>Conclusions</h4>  Our results addressed limitations of standard qPCR-based methods for the study of mtDNA DAMPs. Beyond addressing confounding NUMT, the method identified fragmentomic and variant associations overlooked by qPCR. Cell-free DNA fragmentomic and variant information are well-established biomarkers for cancer, and this method could facilitate similar patient-specific biomarkers in the context of critical illness. The method is composed of commercially available reagents and open source software, which could additionally promote adoption and reproducibility.","authors":["Daly GT","Hartsell EM","Pastukh VM","Roberts JT","Haastrup AI","Purcell LD","Mulekar MS","Files DC","Morris PE","Gillespie MN","Langley RJ."],"year":2025,"journal":"PPR","source":"PPR","preprint":true}],"consensus_view":"The literature consensus is clear that unmodified Humanin directly engages BAX, prevents its conformational activation and mitochondrial translocation, and thereby inhibits MOMP and intrinsic apoptosis. This has been established by biochemical binding assays, siRNA knockdown studies, in vitro liposome/mitochondria assays, and biophysical structural characterization (Morris et al. 2019). HN's anti-apoptotic activity also extends to BimEL and, indirectly, Bak. There is no consensus literature on lipidated or myristoylated HN; this modification is entirely novel territory. The field has focused on point-mutant analogs (notably S14G-HN/HNG) for potency optimization rather than lipid-based membrane targeting strategies. The concept that BAX engagement is a membrane-proximate event is supported by Morris et al.'s finding that BAX's membrane-associating C-terminal helix is required for HN-driven fiber formation.","knowledge_gaps":"Several critical gaps exist: (1) The precise binding interface between HN and BAX has not been resolved crystallographically or by NMR — whether the canonical BAX groove (α3-α4/α5-α6 hydrophobic groove) or the α1-α2 region is engaged by HN is unknown, making the structural prediction in the hypothesis speculative. (2) No study has examined any lipidated or membrane-anchored form of HN; the effect of N-terminal acylation on HN helical structure, BAX binding affinity, and MOMP inhibition is completely uncharacterized. (3) The relative contribution of cytosolic vs. membrane-proximate BAX inhibition to HN's overall anti-apoptotic effect has not been quantitatively dissected. (4) Whether increased local MOM concentration of HN (as a myristoylated analog would achieve) translates to proportionally increased BAX engagement or instead leads to peptide aggregation/sequestration in the bilayer is unknown. (5) The role of HN's N-terminus (Met-1) in BAX binding has not been specifically probed by mutagenesis, so whether the N-terminus is tolerant of bulky hydrophobic modifications is untested.","supporting_evidence":"Multiple lines of evidence support the core hypothesis: (1) Guo et al. 2003 established that HN directly binds BAX and prevents its translocation specifically to mitochondrial membranes, confirming the MOM as the functional site of action. (2) Morris et al. 2019 demonstrated that BAX's C-terminal membrane-targeting helix is required for HN-induced fiber formation, strongly implying the interaction is membrane-proximate and that co-localizing HN and BAX at the MOM could enhance the interaction. (3) The general principle that myristoylation drives MOM enrichment is well-established for other proteins (Src-family kinases, BID/tBID), and the MOM is known to be enriched in the anionic lipids and specific phospholipid compositions that favor myristoyl group insertion. (4) HN is itself a mitochondria-derived peptide, suggesting it has evolved to function in the mitochondrial microenvironment, and membrane-anchoring could restore or amplify this localization. (5) The anti-apoptotic function of HN in cardiomyocyte ischemia-reperfusion (PMID:34896254) and renal I/R (preprint) — contexts characterized by massive BAX-driven MOMP — supports the therapeutic rationale for enhanced potency at the MOM.","challenging_evidence":"Several findings complicate or challenge the hypothesis: (1) Morris et al. 2019 showed HN sequesters BAX into fibers in solution (in vitro, without membranes), suggesting a significant component of HN-BAX interaction occurs in the aqueous/cytosolic phase before membrane association — myristoylation that locks HN to the MOM might actually reduce its ability to intercept BAX in the cytosol where BAX resides in inactive form. (2) Guo et al. 2003 showed HN prevents BAX translocation to mitochondria, implying the key inhibitory event is upstream of membrane insertion; a membrane-anchored HN analog might arrive 'too late' in the BAX activation sequence. (3) Luciano et al. 2005 showed HN binds BimEL (a cytosolic BH3-only protein) independently of BAX; N-terminal myristoylation may abolish this complementary cytosolic anti-apoptotic mechanism, reducing overall efficacy. (4) The hypothesis assumes the HN N-terminus (Met-1) is not critical for BAX binding, but this has not been tested; the myristoyl group is bulky (C14 acyl chain) and could sterically clash with the BAX binding interface or disrupt HN helix initiation. (5) Myristoylated peptides can partition non-specifically into multiple intracellular membranes (ER, plasma membrane, nuclear envelope) and may trigger aggregation or loss of specificity rather than selective MOM enrichment, as myristoylation alone (without an additional electrostatic 'second signal') is often insufficient for specific organelle targeting. (6) No experimental data in the retrieved literature directly supports any lipidated HN analog retaining or gaining anti-apoptotic activity."},"caveats":["in silico prediction only — requires wet lab validation","single-run prediction (not ensembled)","predicted properties may not reflect real-world biological behavior","this is research, not medical advice","FAILED verdict reflects a tool-limit failure (non-standard lipid modification not supported by current AlphaFold-derived pipelines) — not a biological invalidation of the myristoylation hypothesis","heuristic peptide profile metrics (aggregation, stability, BBB, half-life) are sequence-based estimates of the unmodified Humanin backbone only — they do not reflect the myristoyl modification or BAX engagement","myristoylation alone may be insufficient for selective mitochondrial outer membrane targeting without a complementary electrostatic second signal — non-specific membrane partitioning is a known risk","N-terminal myristoylation of Humanin has no experimental precedent in the retrieved literature; all claims about predicted behavior are speculative"],"works_cited":[{"pmid_or_doi":"12732850","title":"Humanin peptide suppresses apoptosis by interfering with Bax activation","year":2003,"relevance":"Foundational paper demonstrating direct HN–BAX binding, prevention of BAX translocation to mitochondrial membranes, and suppression of cytochrome c release; directly establishes the BAX engagement mechanism central to the hypothesis."},{"pmid_or_doi":"31690630","title":"Humanin induces conformational changes in the apoptosis regulator BAX and sequesters it into fibers, preventing mitochondrial outer-membrane permeabilization","year":2019,"relevance":"Most mechanistically detailed study of HN–BAX interaction; shows BAX undergoes structural rearrangements, that the BAX C-terminal membrane-anchoring helix is required for HN-induced fibrillation, and that anti-apoptotic HN mutations disrupt fiber morphology — directly relevant to the membrane-proximate engagement model in the hypothesis."},{"pmid_or_doi":"15655255","title":"Humanin: after the discovery","year":2004,"relevance":"Confirms that intracellularly overexpressed HN suppresses mitochondria-mediated apoptosis by inhibiting BAX activity in cell-based studies, validating the in vitro biochemical findings."},{"pmid_or_doi":"15661735","title":"Cytoprotective peptide humanin binds and inhibits proapoptotic Bcl-2/Bax family protein BimEL","year":2005,"relevance":"Shows HN has additional anti-apoptotic targets beyond BAX (BimEL, Bak), complicating interpretation of BAX-specific effects; also demonstrates that HN mutants with abolished BimEL binding lose cytoprotection, indicating binding interface integrity is functionally critical."},{"pmid_or_doi":"15106598","title":"Unravelling the role of Humanin","year":2004,"relevance":"Reviews the dual mechanisms of HN action (intracellular BAX inhibition and extracellular receptor-mediated signaling) and raises oncogenic implications, relevant for understanding the full target context."},{"pmid_or_doi":"33130077","title":"Humanin: A mitochondrial-derived peptide in the treatment of apoptosis-related diseases","year":2021,"relevance":"Summarizes HN's anti-apoptotic signaling including BCL-2 family interactions and JAK/STAT pathway modulation, providing disease context and confirming BAX regulation as a key mechanism."},{"pmid_or_doi":"34626746","title":"Humanin and Alzheimer's disease: The beginning of a new field","year":2022,"relevance":"Provides historical and mechanistic context for HN discovery and its multiple anti-cell death actions, including antagonism of AD-associated neuronal apoptosis."},{"pmid_or_doi":"34896254","title":"Cardio-protective role of Humanin in myocardial ischemia-reperfusion","year":2022,"relevance":"Demonstrates HN's anti-apoptotic and cytoprotective role in cardiomyocytes under ischemia-reperfusion stress, a context highly dependent on BAX/MOMP regulation at the mitochondrial outer membrane."},{"pmid_or_doi":"37106758","title":"Humanin and Its Pathophysiological Roles in Aging: A Systematic Review","year":2023,"relevance":"Systematic review contextualizing HN's cytoprotective role across aging-related diseases, confirming mitochondrial function preservation as a central mechanism."},{"pmid_or_doi":"27082450","title":"Humanin: Functional Interfaces with IGF-I","year":2016,"relevance":"Documents HN's extracellular signaling role via IGF-I axis, representing a mechanism pathway distinct from intracellular BAX inhibition — relevant for anticipating off-target effects of a membrane-anchored myristoylated analog."},{"pmid_or_doi":"10.21203/rs.3.rs-9040130/v1","title":"Renoprotective Effect of S14G-Humanin on Renal Ischemia/Reperfusion Injury by Activation of STAT3 and ERK 1/2 Signal Transduction Pathways in Rats","year":2026,"relevance":"Preprint demonstrating that the HNG analog (S14G point mutant) retains anti-apoptotic and mitochondrial-protective activity in vivo, providing a precedent that HN analogs with single substitutions can retain function — though lipidation is a far more drastic modification."}]},"onchain":{"hash":null,"signature":null,"data_hash":null,"logged_at":null,"explorer_url":null},"ipfs_hash":null,"created_at":"2026-05-04T08:52:35.318584+00:00","updated_at":"2026-05-04T08:55:57.141750+00:00"}