Interferon-stimulated gene TDRD7 interacts with AMPK and inhibits its activation to suppress viral replication and pathogenesis

Abstract

ABSTRACT Many viruses activate cellular autophagy in infected cells to facilitate their replication. Recently, we identified an interferon (IFN)-stimulated gene (ISG) Tudor domain containing 7 (TDRD7), which inhibits viral replication by blocking autophagy pathway. Here, we present a molecular mechanism for TDRD7 action and its relative contribution to protection against viral pathogenesis. TDRD7 inhibited the activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK), a kinase required for initiating autophagy. Mechanistically, TDRD7 interacted directly with AMPK in the cytosolic compartment. Domain-mapping analyses revealed C-terminal Tudor domain of TDRD7 interacted with auto-inhibitory domain of AMPK. Deletion of Tudor domains abolished anti-AMPK and antiviral activities of TDRD7. We evaluated physiological relevance of TDRD7 function against viral replication using newly engineered TDRD7 knockout mice and the derived primary cells. TDRD7 knockout primary cells displayed increased AMPK activation, which led to a higher viral load. Subsequently, TDRD7 knockout mice showed enhanced susceptibility upon intranasal Sendai virus infection. Therefore, our study revealed a new antiviral function of IFN, mediated by TDRD7-AMPK, inhibiting viral replication and pathogenesis. IMPORTANCE Virus infection triggers induction of interferon (IFN)-stimulated genes (ISGs), which ironically inhibit viruses themselves. We identified Tudor domain-containing 7 (TDRD7) as a novel antiviral ISG, which inhibits viral replication by interfering with autophagy pathway. Here, we present a molecular basis for autophagy inhibitory function of TDRD7. TDRD7 interacted with adenosine monophosphate (AMP)-activated protein kinase (AMPK), the kinase that initiates autophagy, to inhibit its activation. We identified domains required for the interaction; deleting AMPK-interacting domain blocked antiAMPK and antiviral activities of TDRD7. We used primary cells and mice to evaluate the TDRD7-AMPK antiviral pathway. TDRD7-deficient primary mouse cells exhibited enhanced AMPK activation and viral replication. Finally, TDRD7 knockout mice showed increased susceptibility to respiratory virus infection. Therefore, our study revealed a new antiviral pathway of IFN and its contribution to host response. Our results have therapeutic potential; a TDRD7-derived peptide may be an effective AMPK inhibitor with application as antiviral agent.