Coxsackievirus B3 targets TFEB to disrupt lysosomal function.

Coxsackievirus B3 (CVB3) is a prevalent etiological agent for viral myocarditis and neurological disorders, particularly in infants and young children. Virus-encoded proteinases have emerged as cytopathic factors that contribute to disease pathogenesis in part through targeting the cellular recycling machinery of autophagy. Although it is appreciated that CVB3 can usurp cellular macroautophagy/autophagy for pro-viral functions, the precise mechanisms by which viral proteinases disrupt autophagy remain incompletely understood. Here we identified TFEB (transcription factor EB), a master regulator of autophagy and lysosome biogenesis, as a novel target of CVB3 proteinase 3 C. Time-course infections uncovered a significant loss of full-length TFEB and the emergence of a lower-molecular mass (~63 kDa) fragment. Cellular and cleavage assays revealed the involvement of viral proteinase 3 C in the proteolytic processing of TFEB, while site-directed mutagenesis identified the site of cleavage after glutamine 60. Assessment of TFEB transcriptional activity using a reporter construct discovered a loss of function of the cleavage fragment despite nuclear localization and retaining of the ability of DNA and protein binding. Furthermore, we showed that CVB3 infection was also able to trigger cleavage-independent nuclear translocation of TFEB that relied on the serine-threonine phosphatase PPP3/calcineurin. Finally, we demonstrated that both TFEB and TFEB [Δ60] serve roles in viral egress albeit through differing mechanisms. Collectively, this study reveals that CVB3 targets TFEB for proteolytic processing to disrupt host lysosomal function and enhance viral infection.ACTB: actin beta; CLEAR: coordinated lysosomal enhancement and regulation; CVB3: coxsackievirus B3; DAPI: 4',6-diamidino-2-phenylindole; GFP: green fluorescent protein; LAMP1: lysosomal associated membrane protein 1; LTR: LysoTracker Red; PPP3/calcineurin: protein phosphatase 3; PPP3CA: protein phosphatase 3 catalytic subunit A; p-TFEB: phospho-Ser211 TFEB; si-CON: scramble control siRNA; TFEB: transcription factor EB; TFEB [Δ60]: TFEB cleavage fragment that lacks the first 60 amino acids; VP1: viral capsid protein 1.