title: Enhancement of HIV-1-induced syncytium formation in T cells by the tyrosyl kinase p56lck.
abstract: The CD4 glycoprotein is the primary cellular receptor for human immunodeficiency virus type 1 (HIV-1) and has also been reported to be physically associated with p56lck, a tyrosyl protein kinase p56lck is a member of the src family of nonreceptor protein-tyrosine kinases and is expressed predominantly in T lymphocytes. Our objective was to study the effect of p56lck on the biology of HIV-1. For this purpose, we have stably transfected two human p56lck negative T cell lines (C8166-45 and MT-2) with plasmids encoding for this cellular protein. Following coculture with HIV-1-infected cells or infection with cell-free virus, p56lck-expressing cell lines showed a greater propensity for virus-mediated syncytium formation than parental p56lck-negative cells. The enhancement of HIV-1-induced syncytium formation was not associated with the kinase activity of p56lck, as demonstrated by experiments using a kinase-deficient mutant. However, the physical interaction between CD4 and p56lck was shown to be necessary to obtain the enhancement of syncytium formation since a mutated version of p56lck, which is deficient in its capacity to associate with CD4, did not lead to an increase in virus-mediated cell-to-cell fusion events. Finally, we determined that cells transfected with wild-type and kinase-negative mutant p56lck showed a reduced rate of CD4 endocytosis compared to parental p56lck-negative cells. Together, these results suggest that p56lck can be seen as an accessory molecule facilitating HIV-1-mediated syncytium formation in T cells by a mechanism involving the stabilization of the CD4 molecule at the cell surface.
authors.affiliation: Centre de Recherche en Infectiologie, Centre Hospitalier Universitaire de Québec, Ste-Foy, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Briand
authors.forename: B
authors.initials: B
authors.lastname: Barbeau
authors.forename: J
authors.initials: J
authors.lastname: Corbeil
authors.forename: M
authors.initials: M
authors.lastname: Tremblay
mesh_terms: D002460:Cell Line; D002461:Cell Line, Transformed; D015726:Giant Cells / Q000821:virology; D015497:HIV-1 / Q000472:pathogenicity*; D006801:Humans; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism / Q000821:virology*; D014779:Virus Replication; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D019061:src-Family Kinases