title: Human immunodeficiency virus type 1 Tat regulates endothelial cell actin cytoskeletal dynamics through PAK1 activation and oxidant production.
abstract: Human immunodeficiency virus type 1 Tat exerts prominent angiogenic effects which may lead to a variety of vasculopathic conditions in AIDS patients. Because endothelial cells undergo prominent cytoskeletal rearrangement during angiogenesis, we investigated the specific effects of Tat on the endothelial cell actin cytoskeleton. Glutathione S-transferase (GST)-Tat, at a level of 200 ng/ml (equivalent to 52 ng of Tat/ml), caused stress fiber disassembly, peripheral retraction, and ruffle formation in human umbilical vein endothelial cells (HUVEC) and human lung microvascular endothelial cells. At 600 ng of GST-Tat/ml (157 ng of Tat/ml), actin structures were lost, and severe cytoskeletal collapse occurred. In contrast, GST-Tat harboring mutations within either the cysteine-rich or basic domains exerted minimal effects on the endothelial cytoskeleton. HUVEC expressing a DsRed-Tat fusion protein displayed similar actin rearrangements, followed by actin collapse, whereas neighboring nontransfected cells retained normal actin structures. Because active mutants of p21-activated kinase 1 (PAK1) induce identical changes in actin dynamics, we hypothesized that Tat exerts its cytoskeletal effects through PAK1. GST-Tat activated PAK1 within 5 min, and adenovirus delivery of a kinase-dead PAK1 [PAK1(K298A)] completely prevented cytoskeletal collapse induced by GST-Tat or DsRed-Tat and also blocked downstream activation of c-Jun N-terminal kinase. Further, GST-Tat increased phosphorylation of the NADPH oxidase subunit p47(phox) and caused its rapid redistribution to membrane ruffles. PAK1(K298A) blocked p47(phox) phosphorylation, and interference with NADPH oxidase function through superoxide scavenging or through expression of a transdominant inhibitor, p67(V204A), prevented GST-Tat-induced alterations in the actin cytoskeleton. We conclude that Tat induces actin cytoskeletal rearrangements through PAK1 and downstream activation of the endothelial NADPH oxidase.
authors.affiliation: The University of Texas Southwestern Medical Center and the Dallas Veterans Administration Medical Center, Dallas, Texas 75216, USA.
authors.forename: Ru Feng
authors.initials: RF
authors.lastname: Wu
authors.forename: Ying
authors.initials: Y
authors.lastname: Gu
authors.forename: You Cheng
authors.initials: YC
authors.lastname: Xu
authors.forename: Stefania
authors.initials: S
authors.lastname: Mitola
authors.forename: Federico
authors.initials: F
authors.lastname: Bussolino
authors.forename: Lance S
authors.initials: LS
authors.lastname: Terada
mesh_terms: D000199:Actins / Q000378:metabolism*; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D004730:Endothelium, Vascular / Q000821:virology; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D015696:Gene Products, tat / Q000235:genetics / Q000378:metabolism*; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D015497:HIV-1 / Q000378:metabolism / Q000472:pathogenicity*; D006801:Humans; D019255:NADPH Oxidases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014161:Transduction, Genetic; D014471:Umbilical Veins; D054462:p21-Activated Kinases; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D000199:Actins; D015696:Gene Products, tat; D011993:Recombinant Fusion Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; D019255:NADPH Oxidases; D005982:Glutathione Transferase; C515903:PAK1 protein, human; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases