Targeting LAMP2A enhances SELENBP1 expression and suppresses malignant behaviors in HNSCC

Abstract Lysosome-Associated Membrane Protein Type 2A (LAMP2A) serves as the critical rate-limiting component of chaperone-mediated autophagy (CMA), governing substrate translocation into lysosomes. Accumulating studies indicate that LAMP2A downregulation leads to CMA impairment in multiple cancer malignancies. In this study, we found that LAMP2A is significantly upregulated in head and neck squamous cell carcinoma (HNSCC) compared to normal tissues. Cell functional studies performed on FaDu and CAL-27 cells showed that downregulation of LAMP2A inhibited cell proliferation and stemness, and induced cell apoptosis. Since CMA specifically targets proteins containing a pentapeptide motif (KFERQ-like motif) in a LAMP2A-dependent manner, we further employed an integrated proteomic-interactomic approach combined with KFERQ motif analysis. This comprehensive strategy identified Selenium Binding Protein 1 (SELENBP1) as a novel putative CMA substrate in HNSCC. Subsequent validation confirmed that knockdown of CMA receptor LAMP2A significantly increased SELENBP1 protein levels both in vitro and in vivo. CO-IP assays confirmed that SELENBP1 interacts with the CMA chaperone protein heat shock cognate 71 kDa protein (HSPA8) in a KFERQ motif (“EKVIQ”)-dependent manner. Overexpression of SELENBP1 attenuated HNSCC cell proliferation and viability. Most importantly, silencing of SELENBP1 partially rescued the tumor-suppressive phenotypes induced by LAMP2A knockdown, suggesting that SELENBP1 mediated the effects of LAMP2A knockdown on HNSCC. This study provides insights into the role of the LAMP2A-CMA-SELENBP1 axis in the development of novel therapies for HNSCC. Implications: This study provides a novel insight into the role of CMA during the pathogenesis of HNSCC.