Moroi M, Ohnuma M, Komatsu N, Miura Y, Sato T, Jung S M
Department of Protein Biochemistry, Kurume University, Japan.
Biochim Biophys Acta. 1993 Jun 6;1177(2):139-46. doi: 10.1016/0167-4889(93)90033-l.
The expressions of platelet-specific glycoprotein(GP)s Ib, IIb and IIIa were analyzed in 2 megakaryoblastic cell lines: CMK and UT-7. Phorbol-12 myristate 13-acetate (PMA) treatment of CMK induced expressions of GPs IIb and IIIa that peaked on the 4th day post-treatment, while treated UT-7 cells showed maximal levels of these GPs during the 6-8th days. Antibody staining to detect the formation of GPIb alpha after PMA induction showed the presence of the intact GP in UT-7 and the degraded form in CMK. In UT-7, synthesis of GPIIb mRNA increased on days 4-6 after PMA treatment, in parallel with the increase of GPIIb. PMA increased the cytoskeletal protein (actin and myosin) contents in both lines, but in contrast to the two GPs, the increase in these proteins started immediately after PMA addition to the cells. Cell surface proteins of CMK and UT-7 cells were rapidly modified after PMA induction. Especially notable were the degradations of 93-kDa and 140-kDa proteins that occurred on days 1-2 after PMA treatment. These studies demonstrate that the expression of platelet-specific proteins shows a different time dependency than the increment of cytoskeletal proteins, indicating that the syntheses of these two classes of proteins are most likely induced through different mechanisms.
在2种巨核母细胞系CMK和UT-7中分析了血小板特异性糖蛋白（GP）Ib、IIb和IIIa的表达。用佛波醇-12肉豆蔻酸酯13-乙酸酯（PMA）处理CMK可诱导GP IIb和IIIa的表达，在处理后第4天达到峰值，而处理后的UT-7细胞在第6 - 8天显示出这些GP的最高水平。用抗体染色检测PMA诱导后GPIbα的形成，结果显示UT-7中存在完整的GP，而CMK中存在降解形式。在UT-7中，PMA处理后第4 - 6天GPIIb mRNA的合成增加，与GPIIb的增加平行。PMA增加了两种细胞系中细胞骨架蛋白（肌动蛋白和肌球蛋白）的含量，但与两种GP不同的是，这些蛋白的增加在PMA加入细胞后立即开始。PMA诱导后，CMK和UT-7细胞的细胞表面蛋白迅速发生改变。特别值得注意的是，在PMA处理后第1 - 2天发生了93-kDa和140-kDa蛋白的降解。这些研究表明，血小板特异性蛋白的表达与细胞骨架蛋白的增加表现出不同的时间依赖性，表明这两类蛋白的合成很可能是通过不同的机制诱导的。
