Picornavirus VP3 protein induces autophagy through the TP53-BAD-BAX axis to promote viral replication

Macroautophagy/autophagy and apoptosis are pivotal interconnected host cell responses to viral infection, including picornaviruses. Here, the VP3 proteins of picornaviruses were determined to trigger autophagy, with the autophagic flux being triggered by the TP53-BAD-BAX axis. Using foot-and-mouth disease virus (FMDV) as a model system, we unraveled a novel mechanism of how picornavirus hijacks autophagy to bolster viral replication and enhance pathogenesis. FMDV infection induced both autophagy and apoptosis in vivo and in vitro. FMDV VP3 protein facilitated the phosphorylation and translocation of TP53 from the nucleus into the mitochondria, resulting in BAD-mediated apoptosis and BECN1-mediated autophagy. The amino acid Gly129 in VP3 is essential for its interaction with TP53, and crucial for induction of autophagy and apoptosis. VP3-induced autophagy and apoptosis are both essential for FMDV replication, while, autophagy plays a more important role in VP3-mediated pathogenesis. Mutation of Gly129 to Ala129 in VP3 abrogated the autophagic regulatory function of VP3, which significantly decreased the viral replication and pathogenesis of FMDV. This suggested that VP3-induced autophagy benefits viral replication and pathogenesis. Importantly, this Gly is conserved and showed a common function in various picornaviruses. This study provides insight for developing broad-spectrum antivirals and genetic engineering attenuated vaccines against picornaviruses.Abbreviations: 3-MA, 3-methyladenine; ATG, autophagy related; BAD, BCL2 associated agonist of cell death; BAK1, BCL2 antagonist/killer 1; BAX, BCL2 associated X, apoptosis regulator; BBC3/PUMA, BCL2 binding component 3; BCL2, BCL2 apoptosis regulator; BID, BH3 interacting domain death agonist; BIP-V5, BAX inhibitor peptide V5; CFLAR/FLIP, CASP8 and FADD like apoptosis regulator; CPE, cytopathic effects; CQ, chloroquine; CV, coxsackievirus; DAPK, death associated protein kinase; DRAM, DNA damage regulated autophagy modulator; EV71, enterovirus 71; FMDV, foot-and-mouth disease virus; HAV, hepatitis A virus; KD, knockdown; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; MOI, multiplicity of infection; MTOR, mechanistic target of rapamycin kinase; PML, promyelocytic leukemia; PV, poliovirus; SVA, Seneca Valley virus; TCID50, 50% tissue culture infectious doses; TOR, target of rapamycin. TP53/p53, tumor protein p53; WCL, whole-cell lysate.