Inhibition of ER-to-Golgi transport by coxsackievirus 3 A protein: Biological significance, underlying mechanism and structure-function relationship of 3A.

Abstract

The main objective of the studies described in this thesis was to obtain more insight into the functional and structural aspects of the enterovirus 3A protein. Many viruses modify cellular processes for their own benefit. The enterovirus 3A protein inhibits endoplasmic reticulum (ER)-to-Golgi transport, a function previously suggested to be important for viral suppression of immune responses. We showed that a virus carrying a 3A protein defective in inhibiting ER-to-Golgi transport is indeed less virulent in mice, and we unraveled the mechanism by which 3A inhibits this trafficking step. Evidence is provided that 3A inhibits the activation of the GTPase ADP-ribosylation factor 1 (Arf1), which regulates the recruitment of the COP-I coat complex to membranes. 3A specifically inhibits the function of GBF1, a guanine nucleotide exchange factor for Arf1, by interacting with its N terminus. Furthermore, the extensive structure-function analysis that is described in this thesis has given new insight into the structure of the 3A homodimer and in the importance of dimerization for viral RNA replication and the 3A-mediated inhibition of protein transport.