Ubiquitin-Conjugating Enzyme E2 L3 is Downregulated by the Chikungunya Virus nsP2 Protease.

Abstract

Chikungunya virus (CHIKV) is a mosquito transmitted alphavirus that causes chikungunya fever in humans. The CHIKV non-structural protein 2 (nsP2) is a multifunctional protein that additionally modulates the host cell to dampen the innate immune response and inhibit other cellular processes. To further investigate the interactions of nsP2 with host cells, the protease domain of CHIKV nsP2 (nsP2-pro) is transfected into Hela cells, and differential protein expression is detected by 2D polyacrylamide gel electrophoresis. A total of 21 differentially regulated (six upregulated, 15 downregulated) spots are observed, of which five are identified by mass spectrometry. The downregulation of one of the identified proteins, ubiquitin-conjugating enzyme E2 L3 (UBE2L3) is confirmed by western blotting of both nsP2-pro transfection and CHIKV natural infection, and the downregulation of UBE2L3 is additionally shown to require an enzymatically active nsP2 protease domain. Transfection of full length UBE2L3 into HEK293T/17 cells prior to CHIKV infection reduce levels of infection and E protein expression but do not alter RNA genome levels. These results suggest that UBE2L3 is a cellular target of the CHIKV nsP2 protease, and this possibly mediates the pathogenesis of chikungunya fever.