Tyrosine phosphorylation of the p85 subunit of phosphatidylinositol 3-kinase correlates with high proliferation rates in sublines derived from the Jurkat leukemia

• Published in: The international journal of biochemistry & cell biology Vol. 32; no. 4; pp. 435 - 445
• Main Authors: Martı́nez-Lorenzo, Marı́a José, Anel, Alberto, Monleón, Inmaculada, Sierra, José Juan, Piñeiro, Andrés, Naval, Javier, Alava, Maria A
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01-04-2000
• Subjects: Cell Division - drug effects; Humans; Jurkat Cells; Leukemia; Lymphocyte Specific Protein Tyrosine Kinase p56(lck) - metabolism; p85 subunit of PI3 K; Phosphatidylinositol 3-Kinases - antagonists & inhibitors; Phosphatidylinositol 3-Kinases - metabolism; Phosphorylation; Proliferation; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins c-fyn; Tyrosine - metabolism; Tyrosine phosphorylation; 5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide; AICD, activation-induced cell death; PI3 K, phosphatidylinositol 3-kinase; PTK, protein tyrosine kinase; Leukemia; mAb, monoclonal antibody; SH, src homology domain; PHA, phytohemagglutinin; Proliferation; MTT, 3-; Tyrosine phosphorylation; p85 subunit of PI3 K; TCR, T cell receptor
• ISSN: 1357-2725; 1878-5875
• DOI: 10.1016/S1357-2725(99)00142-9

A prominent tyrosine phosphorylated protein of 85 kDa (p85) was detected in highly proliferative sublines derived from the Jurkat T cell leukemia. We undertook a study to characterize the identity of this protein and its possible role in the hyperproliferative phenotypes observed. Using immunoblot and immunoprecipitation techniques, this protein was characterized as the p85 regulatory subunit of phosphatidylinositol 3-kinase. Cell proliferation and p85 tyrosine phosphorylation was not affected by tyrphostin AG-490, an inhibitor of Jak kinases, wortmannin or LY294002, inhibitors of the activity of the catalytic phosphatidylinositol 3-kinase subunit. Herbimycin-A and PP1, inhibitors of
src-like protein tyrosine kinases, and genistein, a general tyrosine kinase inhibitor, inhibited p85 tyrosine phosphorylation and induced cell death in the sublines. PD98059, an inhibitor of Mek, inhibited cell growth of the sublines, but not that of the parental cells. It was concluded that tyrosine phosphorylation of p85 is associated with highly proliferative tumoral phenotypes, at least in T cell leukemias, independent of the phosphatidylinositol 3-kinase activity of the catalytic subunit.