Cooper H L, Fuldner R, McDuffie E, Braverman R
Laboratory of Tumor Immunology and Biology, National Cancer Institute, Bethesda, MD 20892.
J Immunol. 1990 Aug 15;145(4):1205-13.
Prosolin is a major cytosolic phosphoprotein of proliferating normal PBL. Treatment of growing PBL with phorbol ester (12-O-tetradecanoylphorbol-13-acetate (TPA)) or calcium ionophore (A23187) for 1 h caused phosphorylation of prosolin with the production of up to four prominent phosphorylated forms differing in degree of phosphorylation and/or two-dimensional electrophoretic mobility (peptides B to E). Formation of these phosphopeptides coincided with rapid down-regulation of DNA synthesis. A23187 was particularly effective in inducing phosphorylation of the more highly phosphorylated peptides D and E, suggesting the existence of a (Ca2+)-activated mechanism in their phosphorylation. The T cell leukemia cell lines Jurkat, HuT-78, CCRF-CEM, and Molt-4 showed reduced to absent ability to phosphorylate prosolin peptides rapidly in response to A23187 and also showed diminished down-regulation of DNA synthesis. In leukemic cells treated with both TPA and A23187, peptides B and C were rapidly phosphorylated, but the phosphorylation of peptides D and E seen in normal PBL remained deficient. The T cell leukemic cells appear to have intact a TPA-activated mechanism for phosphorylating prosolin peptides B and C, but share an impairment of a specific Ca2(+)-activated mechanism, possibly a Ca2(+)-dependent protein kinase, required for phosphorylation of prosolin phosphopeptides D and E. The degree of rapid down-regulation of DNA synthesis was correlated with degree of phosphorylation of peptide E in PBL and in three of four T cell leukemic cell lines. Thus, rapid phosphorylation of prosolin may mediate responses to TPA and A23187 in normal proliferating PBL, including down-regulation of DNA synthesis. A deficiency of this pathway in leukemic T cells may impede their response to physiologic growth regulatory signals utilizing this pathway and contribute to unrestrained cell growth.
前胰岛素原是正常增殖性外周血淋巴细胞的一种主要胞质磷蛋白。用佛波酯（12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯（TPA））或钙离子载体（A23187）处理生长中的外周血淋巴细胞1小时，会导致前胰岛素原磷酸化，产生多达四种显著的磷酸化形式，其磷酸化程度和/或二维电泳迁移率不同（肽段B至E）。这些磷酸肽的形成与DNA合成的快速下调同时发生。A23187在诱导磷酸化程度更高的肽段D和E的磷酸化方面特别有效，表明在其磷酸化过程中存在一种（Ca2 +）激活机制。T细胞白血病细胞系Jurkat、HuT - 78、CCRF - CEM和Molt - 4显示出对A23187快速磷酸化前胰岛素原肽段的能力降低或缺失，并且DNA合成的下调也减弱。在用TPA和A23187处理的白血病细胞中，肽段B和C迅速磷酸化，但在正常外周血淋巴细胞中所见的肽段D和E的磷酸化仍然不足。T细胞白血病细胞似乎具有完整的TPA激活机制来磷酸化前胰岛素原肽段B和C，但共同存在一种特定Ca2（+）激活机制的损伤，可能是一种Ca2（+）依赖性蛋白激酶，它是前胰岛素原磷酸肽段D和E磷酸化所必需的。DNA合成快速下调的程度与外周血淋巴细胞以及四个T细胞白血病细胞系中的三个中肽段E的磷酸化程度相关。因此，前胰岛素原的快速磷酸化可能介导正常增殖性外周血淋巴细胞对TPA和A23187的反应，包括DNA合成的下调。白血病T细胞中该途径的缺陷可能会阻碍它们对利用该途径的生理生长调节信号的反应，并导致细胞生长不受控制。
