Abstract

Coxsackievirus B3 (CVB3) belongs to the genus Enterovirus of the family Picornaviridae and can cause acute acinar pancreatitis in adults. However, the molecular mechanisms of pathogenesis underlying CVB3-induced acute pancreatitis have remained unclear. In this study, we discovered that CVB3 capsid protein VP1 inhibited pancreatic cell proliferation and exerted strong cytopathic effects on HPAC cells. Through yeast two-hybrid, co-immunoprecipitation, and confocal microscopy, we show that Menage a trois 1 (MAT1), a subunit of the Cdk-Activating Kinase (CAK) complex involved in cell proliferation and transcription, is a novel interaction protein with CVB3 VP1. Moreover, CVB3 VP1 inhibited MAT1 accumulation and localization, thus interfering with its interaction with CDK7. Furthermore, CVB3 VP1 could suppress CAK complex enzymic phosphorylation activity towards RNA Pol II and CDK4/6, direct substrates of CAK. VP1 also suppresses phosphorylation of retinoblastoma protein (pRb), an indirect CAK substrate, especially at phospho-pRb Ser780 and phospho-pRb Ser807/811 residues, which are associated with cell proliferation. Finally, we present evidence using deletion mutants that the C-terminal domain (VP1-D8, 768-859aa) is the minimal VP1 region required for its interaction with MAT1, and furthermore, VP1-D8 alone was sufficient to arrest cells in G1/S phase as observed during CVB3 infection. Taken together, we demonstrate that CVB3 VP1 can inhibit CAK complex assembly and activity through direct interaction with MAT1, to block MAT1-mediated CAK-CDK4/6-Rb signaling, and ultimately suppress cell proliferation in pancreatic cells. These findings substantially extend our basic understanding of CVB3-mediated pancreatitis, providing strong candidates for strategic therapeutic targeting.

Highlights

  • Cholelithiasis and alcoholism are the most common risk factors of acute pancreatitis (AP)

  • We show that Coxsackievirus B3 (CVB3) VP1 could lead to inhibit cell proliferation and exert strong cytopathic effects on pancreatic cells

  • The interaction decreases the amount of Menage a trois 1 (MAT1), but interferes with MAT1 binding to CDK7

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Summary

Introduction

Cholelithiasis and alcoholism are the most common risk factors of acute pancreatitis (AP). Coxsackie Virus group B3 (CVB3), in genus Enterovirus of family Picornaviridae, can cause a variety of human diseases, including myocarditis, pancreatitis, and can even lead to sudden infant death [1,2,3,4,5,6,7]. B-cell epitopes located on VP1 (VP1 1–15 aa, VP1 21–35 aa, and VP1 229–243 aa) and T-cell epitopes on VP1 (VP1 681– 700 aa, VP1 721–740 aa, and VP1 771–790 aa) have been considered ideal vaccine candidates for protection against CVB3 infection [8,9]. Our previous work identified Golgi Matrix Protein 130 (GM130) as a direct intracellular target of CVB3 VP1, and indicated that the interaction between VP1 and GM130 could disrupt the structure of the Golgi ribbon [14]. Few studies have reported the effects of VP1 on cell proliferation and its direct protein targets in cells

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