MAP1LC3A

MAP1LC3A stands for microtubule-associated protein 1 light chain 3 alpha, a human gene that encodes the LC3A protein, a member of the autophagy-related LC3 family. LC3A is a homolog of yeast Atg8 and plays a core role in autophagosome formation and autophagic turnover. It is widely used in research as a marker of autophagosomes and autophagic activity.

In cells, MAP1LC3A is translated as a precursor that is proteolytically cleaved by the cysteine protease ATG4 to generate the cytosolic LC3-I form. LC3-I is then activated for conjugation to phosphatidylethanolamine (PE) through the actions of the ubiquitin-like enzymes ATG7 (E1-like) and ATG3 (E2-like), in conjunction with the ATG12–ATG5–ATG16L1 complex. The result is LC3-II, a lipidated form that associates with autophagosomal membranes and participates in autophagosome maturation and cargo recruitment. LC3-II can be deconjugated back to LC3-I by ATG4, providing a mechanism to recycle LC3 for subsequent autophagic cycles.

There are three LC3 family members in humans: LC3A (MAP1LC3A), LC3B (MAP1LC3B), and LC3C (MAP1LC3C). They share conserved functions in autophagy but can differ in localization, regulation, and cargo interactions. LC3 proteins are commonly measured as LC3-I and LC3-II by Western blot, and LC3 puncta are observed by fluorescence microscopy as a proxy for autophagosomes.

MAP1LC3A is ubiquitously expressed and contributes to cellular responses to stress that regulate autophagy. Because autophagy is implicated in development, infection, neurodegeneration, and cancer, LC3A is routinely used in experimental models to assess autophagic flux.