title: Gag localization and virus-like particle release mediated by the matrix domain of human T-lymphotropic virus type 1 Gag are less dependent on phosphatidylinositol-(4,5)-bisphosphate than those mediated by the matrix domain of HIV-1 Gag.
abstract: The human immunodeficiency virus type 1 (HIV-1) Gag matrix (MA) domain facilitates Gag targeting and binding to the plasma membrane (PM) during virus assembly. Interaction with a PM phospholipid, phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P(2)], plays a key role in these MA functions. Previous studies showed that overexpression of polyphosphoinositide 5-phosphatase IV (5ptaseIV), which depletes cellular PI(4,5)P(2), mislocalizes HIV-1 Gag to the cytosol and greatly reduces HIV-1 release efficiency. In this study, we sought to determine the role of the MA-PI(4,5)P(2) interaction in Gag localization and membrane binding of a deltaretrovirus, human T-lymphotropic virus type 1 (HTLV-1). We compared the chimeric HIV-1 Gag (HTMA), in which MA was replaced with HTLV-1 MA, with wild-type HIV-1 and HTLV-1 Gag for PI(4,5)P(2) dependence. Our results demonstrate that, unlike HIV-1 Gag, subcellular localization of and VLP release by HTLV-1 and HTMA Gag were minimally sensitive to 5ptaseIV overexpression. These results suggest that the interaction of HTLV-1 MA with PI(4,5)P(2) is not essential for HTLV-1 particle assembly. Furthermore, liposome-binding analyses showed that both HTLV-1 and HTMA Gag can bind membrane efficiently even in the absence of PI(4,5)P(2). Efficient HTLV-1 Gag binding to liposomes was largely driven by electrostatic interaction, unlike that of HIV-1 Gag, which required specific interaction with PI(4,5)P(2). Furthermore, membrane binding of HTLV-1 Gag in vitro was not suppressed by RNA, in contrast to HIV-1 Gag. Altogether, our data suggest that Gag targeting and membrane binding mediated by HTLV-1 MA does not require PI(4,5)P(2) and that distinct mechanisms regulate HIV-1 and HTLV-1 Gag membrane binding.
authors.affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, 1150 W. Medical Center Dr., Ann Arbor, MI 48109, USA.
authors.forename: Jingga
authors.initials: J
authors.lastname: Inlora
authors.forename: Vineela
authors.initials: V
authors.lastname: Chukkapalli
authors.forename: David
authors.initials: D
authors.lastname: Derse
authors.forename: Akira
authors.initials: A
authors.lastname: Ono
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D015683:Gene Products, gag / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics; D015368:Human T-lymphotropic virus 1 / Q000235:genetics / Q000502:physiology*; D006801:Humans; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D011995:Recombination, Genetic; D014763:Viral Matrix Proteins / Q000378:metabolism*; D057074:Virus Release
chemical_list: D015683:Gene Products, gag; D019269:Phosphatidylinositol 4,5-Diphosphate; D014763:Viral Matrix Proteins