ANXA6 suppresses the tumorigenesis of cervical cancer through autophagy induction.

BACKGROUND

Autophagy is an intracellular degradation pathway conserved in eukaryotes. ANXA6 (annexin A6) belongs to a family of calcium-dependent membrane and phospholipid-binding proteins. Here, we identify ANXA6 as a newly synthesized protein in starvation-induced autophagy and validate it as a novel autophagy modulator that regulates autophagosome formation.

RESULTS

ANXA6 knockdown attenuates starvation-induced autophagy, while restoration of its expression enhances autophagy. GO (gene ontology) analysis of ANXA6 targets showed that ANXA6 interacts with many RAB GTPases and targets endocytosis and phagocytosis pathways, indicating that ANXA6 exerts its function through protein trafficking. ATG9A (autophagy-related 9A) is the sole multispanning transmembrane protein and its trafficking through recycling endosomes is an essential step for autophagosome formation. Our results showed that ANXA6 enables appropriate ATG9A vesicle trafficking from endosomes to autophagosomes through RAB proteins or F-actin. In addition, restoration of ANXA6 expression suppresses mTOR (mammalian target of rapamycin) activity through the inhibition of the PI3K (phosphoinositide 3-kinase)-AKT and ERK (extracellular signal-regulated kinase) signaling pathways, which is a negative regulator of autophagy. Functionally, ANXA6 expression is correlated with LC3 (microtubule-associated protein 1 light chain 3) expression in cervical cancer, and ANXA6 inhibits tumorigenesis through autophagy induction.

CONCLUSIONS

Our results reveal an important mechanism for ANXA6 in tumor suppression and autophagy regulation.