HIV Research Today is a free monthly online journal that collates and summarizes the latest research about HIV, including details on human immunodeficiency virus, testing, treatment, prevention, vaccines, aids. | ||||||||
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Identification of a region within the cytoplasmic domain of the subtype B Vpu protein of human immunodeficiency virus type 1 (HIV-1) that is responsible for retention in the golgi complex and its absence in the Vpu protein from a subtype C HIV-1.Pacyniak E, Gomez ML, Gomez LM, Mulcahy ER, Jackson M, Hout DR, Wisdom BJ, Stephens EB Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, Kansas 66160, USA. The structure of the Vpu protein of human immunodeficiency virus type 1 (HIV-1) is composed of a short Nterminal domain (NTD), a transmembrane domain (TM), and a cytoplasmic domain (CD). Previous studies have shown that the Vpu protein from subtype B HIV-1 is transported predominantly to the rough endoplasmic reticulum (RER)/Golgi complex compartments of the cell and is not incorporated into virions. Using a previously described VpuEGFP reporter system in which the Vpu protein was fused to the gene for enhanced green fluorescent protein (EGFP), we showed that the subtype B Vpu fusion protein was localized to the RER/Golgi region of the cell, similar to the native protein. In the present study, we show that fusion of the subtype C Vpu to EGFP results in a fusion protein that is transported to the cell surface. Using this reporter system, chimeric Vpu proteins in which the CD of the subtype B and C proteins were exchanged showed that the CD was sufficient for targeting the subtype B protein to the Golgi complex of the cell. Following identification of the cytoplasmic domain as being responsible for intracellular targeting, we then generated a series of mutants in which 13, 23, 31, 38, 51, and 56 amino acids were deleted from the cytoplasmic domain of subtype B Vpu. These deletion mutants were analyzed by SDS-PAGE for size, for membrane localization, and intracellular localization by confocal fluorescence microscopy. Our results indicate that the mutant with the carboxyl-terminal 13 amino acids deleted was still localized to the Golgi complex but mutants with 23, 31, 38, 51, and 56 amino acids from the carboxyl-terminus of the subtype B Vpu were transported to the cell surface. These results suggest that a signal for the retention of the subtype B Vpu within the Golgi complex resides in the second alpha-helical domain. Published 2 June 2005 in AIDS Res Hum Retroviruses, 21(5): 379-94.
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