Humanin

Humanin is a 21 amino acid mitochondria-derived peptide (MAPRGFSCLLLLTSEIDLPVKRRA) encoded within the mitochondrial 16S ribosomal RNA gene (MT-RNR2) in an alternative open reading frame — making it a founding member of the mitochondria-derived peptide (MDP) family alongside MOTS-c and the SHLP (small humanin-like peptide) series.

Humanin was originally identified by Hashimoto et al. (2001) through expression cloning screening for factors that rescue neuronal cells from Alzheimer's disease-related toxicity — specifically, protection against amyloid precursor protein mutant (APP)-induced apoptosis. This discovery established the first known mitochondria-derived cytoprotective peptide and launched the field of mitochondrial retrograde signalling peptides.

The receptor pharmacology of Humanin involves multiple cell-surface receptor systems. Humanin activates the tripartite receptor complex consisting of CNTFR (ciliary neurotrophic factor receptor alpha), WSX-1 (IL-27 receptor alpha), and gp130 (IL-6 signal transducer) — a receptor complex shared with CNTF and other neurotrophic cytokines. This receptor activation drives JAK-STAT3 signalling, activating anti-apoptotic gene transcription (Bcl-2, Bcl-xL) and pro-survival pathways. Humanin also signals through IGFBP-3 (insulin-like growth factor binding protein 3) and IGFBP-3 receptor as a second receptor system.

Neuroprotection research has characterised Humanin across multiple neuronal cell death paradigms: beta-amyloid peptide toxicity, oxidative stress-induced death, glutamate excitotoxicity, and serum deprivation. Published research has established structure-activity relationships showing that Gly14 is the critical residue for neuroprotective activity — G14A substitution abolishes protection.

Metabolic research has connected Humanin to insulin sensitivity, hepatic gluconeogenesis suppression (through STAT3 activation in hepatocytes), and adipogenesis regulation, positioning it alongside MOTS-c in the mitochondrial peptide/metabolic biology research framework.

Humanin potency considerations and experimental design: the extraordinary potency claims in some published Humanin research (picomolar to femtomolar effective concentrations) require careful experimental validation. Prepare Humanin stocks in sterile water or PBS at 1mg/mL, then perform serial dilutions covering a wide range (1fM to 1µM) to characterise the complete concentration-response relationship. Include low-binding tubes and plates (polypropylene, BSA-blocked surfaces) to minimise adsorption losses at the lowest concentrations, which is a significant confound for peptides at sub-nanomolar concentrations.

For CNTFR/WSX-1/gp130 receptor research: use cells expressing the tripartite receptor complex — motor neuron-like NSC-34 cells, primary cortical neurons, or HEK293 cells stably transfected with all three receptor components. Measure STAT3 phosphorylation (Tyr705) by Western blot at 15, 30, and 60 minutes following Humanin application (the primary JAK-STAT signalling readout). Include CNTF (ciliary neurotrophic factor) at published EC50 concentrations as a positive control for the same receptor complex. For selectivity confirmation, use gp130 inhibitor SC144 (10µM pre-treatment) to confirm gp130-dependent signalling. Metabolic research endpoints in hepatocytes: measure glucose output (glucose oxidase assay in conditioned medium, glucagon-stimulated hepatocytes), phospho-STAT3, and phospho-Akt (Ser473) as downstream readouts of Humanin's proposed hepatic insulin-sensitising effects. MW: 2388.8 g/mol. CAS: 313968-35-3. Reconstitute in bacteriostatic water at 1mg/mL. Store lyophilised at -20°C. For laboratory and analytical research purposes only.