Required for both basal and inducible autophagy. Determines the localization of the autophagy-specific PI3-kinase complex PI3KC3-C1 (PubMed:18843052, PubMed:19050071). Plays a role in autophagosome formation and MAP1LC3/LC3 conjugation to phosphatidylethanolamine (PubMed:19270696, PubMed:20713597). Promotes BECN1 translocation from the trans-Golgi network to autophagosomes (PubMed:20713597). Enhances PIK3C3 activity in a BECN1-dependent manner. Essential for the autophagy-dependent phosphorylation of BECN1 (PubMed:23878393). Stimulates the phosphorylation of BECN1, but suppresses the phosphorylation PIK3C3 by AMPK (PubMed:23878393). Binds to STX17-SNAP29 binary t-SNARE complex on autophagosomes and primes it for VAMP8 interaction to promote autophagosome-endolysosome fusion (PubMed:25686604, PubMed:37632749). Modulates the hepatic lipid metabolism (By similarity). {ECO:0000250|UniProtKB:Q8CDJ3, ECO:0000269|PubMed:18843052, ECO:0000269|PubMed:19050071, ECO:0000269|PubMed:19270696, ECO:0000269|PubMed:20713597, ECO:0000269|PubMed:23878393, ECO:0000269|PubMed:25686604, ECO:0000269|PubMed:37632749}. This is the function of ATG14 (autophagy related 14, ENSG00000126775).