Effect of vinblastine on distribution of murine leukemia virus-derived membrane-associated antigens.

Abstract

The effect of vinblastine on the distribution of murine leukemia virus-derived membrane-associated antigens was examined by using the indirect immunofluorescence of 3.7%formaldehyde-fixed MJD-54 (Moloney murine leukemia virus-infected) cells. On fixed, non-drug-treated cells, p30 antigen was distributed homogeneously and diffusely over the cell membrane.When cells were incubated with 10 pAM vinblastine for 1 hr before fixation, the distribution of p30 antigen was greatly changed, fluorescence now being collected into poles (cap-like formation). In contrast to this distribution pattern for p3) antigen, gp7O antigen was distributed in a micropunctate pattern on the cell surface, with or without vinblastine pretreatment. These observations indicate that the distribution patterns of p30 and gp7O membrane antigens are completely different and that they are differently controlled by cytoplasmic microtubules. In addition, because the p30 membrane antigen visualized in these studies most likely represents viral Pr65P. precursor molecules which are localized directly under and associated with the plasma membrane, these results suggest that, under special conditions of fixation, it is possible to obtain a cap-like phenomenon for cytoplasmic (internal) membraneoriented proteins.It now has been generally accepted that the lateral mobility and distribution of externally exposed cell surface proteins are regulated in large part by submembranous cytoskeletal elements (1-6), although there is also some evidence that directed lipid flow in membranes is important as well (7). Such a concept has come mainly from the study of drug effects on the distribution of cell surface proteins. The drugs used include microtubuledepolymerizing agents such as colchicine, nocodazole, and vinblastine (2, 4, 6) and microfilament-depolymerizing agents such as cytochalasin B (4, 8). The distribution of immunoglobulins and concanavalin A receptors on lymphocytes (3, 4, 6) and fibroblasts (1) after treatment with such drugs has been extensively studied by fluorescence microscopy.In the case ofcells chronically infected with murine leukemia virus there are three known classes ofcell membrane-associated proteins that are coded for by the viral genome. Two are externally exposed; (i) glycosylated gag (group-specific antigen) gene products of Mr 80 x 103 and 95 x 103 (9-11) which have been described earlier as "Gross cell surface antigens" and shown not to be incorporated into virus particles (12); and (ii) the env gene products gp7O and pl5E. gp7O exists both at the site ofvirus buds (13,14) and over the cell surface (9, 13); pl5E is embedded directly in the membrane (15). In addition, there is an internally exposed cell membraneassociated protein. This is the major gag gene product, Pr65P9, which is the precursor to the group-specific viral core proteins (p30, p15, p12, and plo) (10,16). It has been localized, by electron microscopic studies, to a position just under the cell membrane (16) and, because it hasa hydrophobic NH2terminus, p15 (17),...

Channel catfish virus: interaction with the cytoskeleton

“…The initial objectives of the present study were to determine if the modification and/or destruction of cytoskeletal elements could hinder or inhibit the production of infectious virus particles. Several precedents exist for this sort of interaction between cytoskeletal elements and virus replication pathways (Richardson & Vance 1978;Banes & Coleman 1980;Satake, McMillan & Luftig 1981;Volkman, Goldsmith & Hess 1987;Volkman 1988;Volkman & Zaal 1990;Hammonds, Denyer, Jackson & Irving 1996). In this study, the present authors demonstrate that intact microtubules and/or vimentin filaments are required for the proper distribution of CCV antigen.…”

Human immunodeficiency virus envelope protein determines the site of virus release in polarized epithelial cells.

“…In the case of alphaviruses, evidence for interactions between envelope and core proteins has been obtained by crosslinking studies (2), and recently it was shown that the nucleocapsid of Semliki Forest virus could interact in vitro with the cytoplasmic domain of the envelope protein p62/E2 (3). The transmembrane protein (pl5E) and the matrix protein (p15) of Moloney murine leukemia virus appeared to be colocalized at the plasma membrane of infected cells as determined by immunofluorescence (4,5), and the transmembrane glycoprotein (gp35) and matrix protein (p19) of Rous sarcoma virus were shown to be closely associated by chemical crosslinking analysis (6). Altered processing of the cytoplasmic domain of the Mason-Pfizer monkey virus glycoprotein was found recently in matrix protein mutants of this virus (35).…”