Hepatitis C Virus NS5A Inhibits YAP1-HSC70 Interaction, Thereby Preventing YAP1 Degradation Via Chaperone-Mediated Autophagy.

Hepatitis C virus (HCV) infection induces chaperone-mediated autophagy (CMA), where the HCV NS5A protein promotes the binding of the molecular chaperone HSC70 to substrate proteins containing a KFERQ motif. HSC70 recognizes this pentapeptide motif and transports substrates to lysosomes for degradation. In this study, we identified a KFERQ motif (324ELLRQ328) in the YAP1 protein, a key regulator of the Hippo pathway, and examined its interaction with HSC70 during HCV infection. To determine whether HSC70 directly binds to this motif, we generated four YAP1 mutants with specific alterations in the KFERQ motif and assessed their binding to HSC70. Among these, the R327A/Q328A mutant showed the greatest reduction in HSC70 binding, indicating that the sequence 324ELLRQ328 functions as the KFERQ motif in YAP1. Further analysis revealed that YAP1 binds to the substrate-binding domain of HSC70. Moreover, shRNA-mediated knockdown of LAMP2A, a critical receptor for CMA, led to increased levels of YAP1, confirming that YAP1 is indeed a CMA substrate. Notably, HSC70 was also found to interact with phosphorylated YAP1 at serine 127 (S127). Although NS5A did not bind directly to YAP1, NS5A expression reduced the binding between YAP1 and HSC70. This suggests that under normal conditions, YAP1 is recognized by HSC70 and degraded via CMA. However, during HCV infection, NS5A interferes with YAP1-HSC70 interaction, preventing YAP1 from being degraded. As a result, YAP1 accumulates in the cytoplasm and subsequently translocates to the nucleus, where YAP1 may activate genes involved in cell proliferation and survival. This mechanism may contribute to HCV-induced pathogenesis.