Blood, Vol. 94 No. 2 (July 15), 1999:
pp. 663-672
The Tat Protein of Human Immunodeficiency Virus Type-1 Promotes
Vascular Cell Growth and Locomotion by Engaging the 
5
1 and
v3 Integrins and by Mobilizing Sequestered Basic Fibroblast
Growth Factor
Giovanni Barillari,
Cecilia Sgadari,
Valeria Fiorelli,
Felipe Samaniego,
Sandra Colombini,
Vittorio Manzari,
Andrea Modesti,
Bala C. Nair,
Aurelio Cafaro,
Michael Stürzl, and
Barbara Ensoli
From the Laboratory of Virology, Istituto Superiore di Sanità,
Rome, Italy; the Department of Experimental Medicine, University
"Tor Vergata," Rome, Italy; the Department of Allergy and
Clinical Immunology, University "La Sapienza," Rome, Italy; the
Institute of Human Virology, University of Maryland at Baltimore,
Baltimore, MD; Advanced BioScience Laboratories Inc, Kensington, MD;
the GSF-National Research Center for Environment and Health, Bavarian
Nordic Research Institute AS, Martinsried, Germany; and the Technical
University of Munich, Institute of Virology, Munich, Germany.
The Tat protein of human immunodeficiency virus type-1 (HIV-1) has
been shown to be released during acute infection of T cells by HIV-1
and to promote angiogenesis and Kaposi's sarcoma (KS) development in
infected individuals. In this study, we investigated the molecular
mechanisms responsible for the angiogenic effects of Tat. The results
shown herein indicate that two different Tat domains cooperate to
induce these effects by different pathways. The
arginine-glycine-aspartic acid (RGD) sequence present at the carboxyterminal of Tat mediates vascular cell migration and invasion by
binding to the 
5
1 and v3 integrins. This interaction also provides endothelial cells with the adhesion signal they require to
grow in response to mitogens. At the same time, the Tat basic sequence
retrieves into a soluble form extracellular basic fibroblast growth
factor (bFGF) bound to heparan sulfate proteoglycans by competing for
heparin-binding sites. This soluble bFGF mediates Tat-induced vascular
cell growth. These effects resemble those of extracellular matrix
proteins, suggesting that Tat enhances angiogenesis and promotes KS
progression by a molecular mimicry of these molecules.
