HIV-1-Tat protein activates phosphatidylinositol 3-kinase/AKT-dependent survival pathways in Kaposi's sarcoma cells

Maria Chiara Deregibus, Vincenzo Cantaluppi, Sophie Doublier, Maria Felice Brizzi, Ilaria Deambrosis, Adriana Albini, Giovanni Camussi

Research output: Contribution to journalArticle

Abstract

In this study we found that Tat protected vincristine-treated Kaposi's sarcoma cells from apoptosis and from down-regulation of several anti-apoptotic genes such as AKT-1, AKT-2, BCL2, BCL-XL, and insulin-like growth factor I and induced the de novo expression of the interleukin-3 gene. Moreover, we found that Tat enhanced phosphorylation of AKT and BAD proteins. The inhibition of phosphatidylinositol 3-kinase with two unrelated pharmacological inhibitors, wortmannin and LY294002, abrogated both the anti-apoptotic effect and the phosphorylation of AKT induced by Tat. After treatment with Tat, the AKT enzymatic activity showed a biphasic increase: an early activation (15 min), independent from protein synthesis; and a delayed activation (24 h), which was significantly decreased upon blockage of protein synthesis. Experiments with a function blocking antivascular endothelial cell growth factor receptor-2 antibody suggested that both the early and delayed AKT activation and the protection from apoptosis were triggered by the interaction of Tat with vascular endothelial cell growth factor receptor-2. Moreover, experiments with function-blocking antibodies directed against insulin-like growth factor I/insulin-like growth factor I receptor or interleukin-3 indicated their involvement in the delayed activation of AKT and their contribution to the anti-apoptotic effect of Tat on vincristine-treated Kaposi's sarcoma cells.

Original languageEnglish
Pages (from-to)25195-25202
Number of pages8
JournalJournal of Biological Chemistry
Volume277
Issue number28
DOIs
Publication statusPublished - Jul 12 2002

ASJC Scopus subject areas

  • Biochemistry

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