Tat-human immunodeficiency virus-1 induces human monocyte chemotaxis by activation of vascular endothelial growth factor receptor-1.
Human immunodeficiency virus-1 (HIV-1) Tat protein can be released by infected cells and activates mesenchymal cells. Among these, monocytes respond to Tat by migrating into tissues and releasing inflammatory mediators. In the present study, we have examined the molecular mechanism of monocyte activation by Tat, showing that this viral protein signals inside the cells through the tyrosine kinase receptor for vascular endothelial growth factor encoded by fms-like tyrosine kinase gene (VEGFR-1/Flt-1). Subnanomolar concentrations of Tat induced monocyte chemotaxis, which was inhibited by cell preincubation with vascular-endothelial growth factor-A (VEGF-A). This desensitisation was specific for VEGF-A, because it not was observed with FMLP. In addition, the soluble form of VEGFR-1 specifically inhibited polarization and migration induced by Tat and VEGF-A, thus confirming the common use of this receptor. Binding studies performed at equilibrium by using radiolabeled Tat showed that monocytes expressed a unique class of binding site, with a kd of approximately 0.2 nmol/L. The binding of radiolabeled Tat to monocyte surface and the cross-linking to a protein of 150 kD was inhibited specifically by an excess of cold Tat or VEGF-A. Western blot analysis with an antibody anti-VEGFR-1/Flt-1 performed on monocyte phosphoproteins immunoprecipitated by an monoclonal antibody anti-phosphotyrosine showed that Tat induced a rapid phosphorylation in tyrosine residue of the 150-kD VEGFR-1/Flt-1. Taken together, these results suggest that biologic activities of HIV-1 Tat in human monocytes may, at least in part, be elicited by activation of VEGFR-1/Flt-1.
Mitola
S
S
Department of Genetics, Biology and Medical Chemistry, Torino, Italy.
Sozzani
S
S
Luini
W
W
Primo
L
L
Borsatti
A
A
Weich
H
H
Bussolino
F
F
D000911:Antibodies, Monoclonal; D001665:Binding Sites; D002634:Chemotaxis, Leukocyte; D016228:Endothelial Growth Factors / Q000378:metabolism; D015696:Gene Products, tat / Q000502:physiology*; D015497:HIV-1 / Q000502:physiology; D006801:Humans; D008222:Lymphokines / Q000378:metabolism; D008970:Molecular Weight; D009000:Monocytes / Q000378:metabolism* / Q000821:virology; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000276:immunology*; D020794:Receptor Protein-Tyrosine Kinases / Q000276:immunology*; D017978:Receptors, Growth Factor / Q000276:immunology*; D042461:Vascular Endothelial Growth Factor A; D040281:Vascular Endothelial Growth Factor Receptor-1; D042442:Vascular Endothelial Growth Factors; D054322:tat Gene Products, Human Immunodeficiency Virus
D000911:Antibodies, Monoclonal; D016228:Endothelial Growth Factors; D015696:Gene Products, tat; D008222:Lymphokines; D011518:Proto-Oncogene Proteins; D017978:Receptors, Growth Factor; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D054322:tat Gene Products, Human Immunodeficiency Virus; D009240:N-Formylmethionine Leucyl-Phenylalanine; D020794:Receptor Protein-Tyrosine Kinases; D040281:Vascular Endothelial Growth Factor Receptor-1