Interaction of the duck Tembusu virus NS1 protein with CCT2 suppresses autophagy and facilitates viral replication

Duck Tembusu virus (DTMUV) has evolved diverse molecular strategies to exploit host cellular factors for efficient viral replication. The chaperonin subunit CCT2, a component of the TCP-1 ring complex, is essential for the proper folding and assembly of oligomeric proteins in host cells. In this study, we report that CCT2 specifically associates with DTMUV non-structural protein 1 (NS1), validated by both endogenous and exogenous co-immunoprecipitation assays, and the interaction domain was mapped to amino acid residues 172-352 in NS1. Overexpression of CCT2 significantly boosts DTMUV replication, whereas its depletion strongly inhibits viral proliferation and spread. NS1 was further shown to be modified by K48- and K63-linked polyubiquitin chains, and NS1-CCT2 interaction may stabilize NS1 through the ubiquitin-proteasome system. More interestingly, CCT2 was found to physically interact with LC3C, a central autophagy effector. NS1-CCT2 interaction interferes with this binding probably via competitive inhibition, resulting in suppression of autophagic signaling. Taken together, our results identify CCT2 as a pivotal host factor restricting DTMUV infection and reveal a previously unrecognized strategy by which the virus exploits disruption of the CCT2-LC3C interaction to impair the chaperone-mediated autophagy pathway and evade host immune responses.