The expression of CD154 by Kaposi's sarcoma cells mediates the anti-apoptotic and migratory effects of HIV-1-TAT protein.
Kaposi's sarcoma (KS) is a malignancy associated to conditions of immune system impairment such as HIV-1 infection and post-transplantation therapy. Here we report that HIV-1-Tat protein, at concentrations well below those detected in AIDS patients, up-regulates the expression of both CD40 and CD154 on KS cells. This occurred also in the presence of vincristine, that at doses shown to induce apoptosis decreased the expression of both CD40 and CD154 on KS cells. The treatment with a soluble CD40-muIg fusion protein (CD40 fp) that prevents the binding of CD154 with cell surface CD40, as well as the transfection with a vector for soluble CD40 (KS sCD40), decreased the anti-apoptotic effect of Tat. Moreover, Tat-induced motility of KS cells was inhibited by soluble CD40 fp. Tat also enhanced the expression of intracellular proteins known to transduce signals triggered by CD40 engagement, in particular TRAF-3. Tat as well as soluble CD154 (sCD154) prevented vincristine-induced reduction of TRAF-3 in KS cells transfected with a vector for neomycin resistance (KS psv-neo), but not in KS sCD40. Immunoprecipitation studies showed that Tat induced CD40 / TRAF-3 association and that this binding was abrogated upon the incubation with the soluble CD40 fp. These data suggest that Tat activates the CD40-CD154 pathway by enhancing the membrane expression of CD40 and in particular of CD154, and by activating the TRAF-3-dependent signaling pathway of CD40. These findings indicate that the CD40-CD154 pathway mediates the anti-apoptotic and migratory effects of HIV-1- Tat, suggesting the potential therapeutic benefits of blocking CD40 activation in HIV-1-associated KS.
Renal and Vascular Immunopathology Laboratory (CeRMS), Department of Internal Medicine, University of Torino, Italy.
V
V
Cantaluppi
M C
MC
Deregibus
L
L
Biancone
I
I
Deambrosis
B
B
Bussolati
A
A
Albini
G
G
Camussi
D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D019013:CD40 Antigens / Q000096:biosynthesis / Q000235:genetics; D023201:CD40 Ligand / Q000096:biosynthesis*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects*; D002467:Cell Nucleus / Q000648:ultrastructure; D002470:Cell Survival / Q000187:drug effects; D004273:DNA, Neoplasm / Q000096:biosynthesis / Q000302:isolation & purification; D015696:Gene Products, tat / Q000494:pharmacology*; D015497:HIV-1 / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D020287:In Situ Nick-End Labeling; D007202:Indicators and Reagents; D020411:Oligonucleotide Array Sequence Analysis; D012514:Sarcoma, Kaposi / Q000378:metabolism*; D014162:Transfection; D054322:tat Gene Products, Human Immunodeficiency Virus
D019013:CD40 Antigens; D004273:DNA, Neoplasm; D015696:Gene Products, tat; D007202:Indicators and Reagents; D054322:tat Gene Products, Human Immunodeficiency Virus; D023201:CD40 Ligand; D020169:Caspases