Autophagy

Definition

Autophagy (from Greek: “self-eating”) is a conserved cellular process in which damaged organelles, misfolded proteins, and other cytoplasmic components are enclosed in double-membrane vesicles (autophagosomes) and delivered to lysosomes for degradation and recycling. It serves as a quality control mechanism critical for cellular homeostasis.

Types and Regulation

Three main forms exist: macroautophagy (the most studied, commonly referred to simply as autophagy), microautophagy, and chaperone-mediated autophagy. The process is regulated by mTOR (mammalian target of rapamycin), which acts as a master inhibitor — when mTOR is active (nutrient-replete conditions), autophagy is suppressed. AMPK activation, caloric restriction, and cellular stress promote autophagy by inhibiting mTOR.

Key autophagy genes (ATG genes) coordinate the formation, elongation, and closure of autophagosomes. LC3-II lipidation is the most widely used biomarker for monitoring autophagic flux in research.

Relevance to Peptide Research

Autophagy intersects with peptide research in several contexts. Peptides that modulate the GH-IGF-1-mTOR axis can indirectly influence autophagic activity. Humanin, a mitochondrial-derived peptide, has been studied for its cytoprotective effects partly mediated through autophagy regulation. Epitalon and other longevity-associated peptides are investigated in the context of age-related decline in autophagic capacity, which contributes to cellular senescence and accumulation of damaged organelles.