TMEM74 (transmembrane protein 74) is a lysosomal and autophagosomal protein that functions as a critical regulator of autophagy through a unique mechanism distinct from canonical pathways. 1 TMEM74 localizes to lysosomes and autophagosomes, and its overexpression induces autophagic vacuolization and increases LC3-II levels. 2 Rather than operating through the BECN1/PI3KC3 complex or ULK1, TMEM74 directly interacts with autophagy proteins ATG16L1 and ATG9A to initiate autophagy nucleation and elongation. 3 Additionally, TMEM74 interacts with the pro-apoptotic protein BIK via its transmembrane domains, inhibiting BIK-induced apoptosis and revealing crosstalk between autophagy and apoptotic pathways. In the nervous system, TMEM74 functions in anxiety regulation through interactions with hyperpolarization-activated cyclic nucleotide-gated 1 (HCN1) channels in basolateral amygdala pyramidal neurons, with genetic deletion causing anxiety-like behaviors in mice. 4 Clinically, TMEM74 shows elevated expression in hepatocellular carcinoma and lung cancer, where it promotes tumor cell proliferation and survival under metabolic stress. 5 High TMEM74 expression correlates with shorter patient survival periods and has been incorporated into prognostic risk models for lung adenocarcinoma and triple-negative breast cancer, 67 identifying it as a potential therapeutic target and diagnostic marker for cancer management.