Hirata F, Matsuda K, Notsu Y, Hattori T, del Carmine R
Proc Natl Acad Sci U S A. 1984 Aug;81(15):4717-21. doi: 10.1073/pnas.81.15.4717.
When murine thymocytes were stimulated by mitogens such as concanavalin A, the Ca2+ ionophore A23187, or 4 beta-phorbol 12-myristate 13-acetate, there was a marked increase of 32P incorporation into immunoprecipitable lipomodulin, a phospholipase inhibitory protein. These compounds enhanced 45Ca2+ influx into thymocytes, which, in turn, increased protein phosphorylation, probably by Ca2+- and phospholipid-dependent protein kinase (protein kinase C). Cyclic 8-bromo-AMP, an inhibitor of lymphocyte mitogenesis, blocked the mitogen-stimulated phosphorylation of lipomodulin, although it stimulated the protein phosphorylation via cyclic AMP-dependent kinase (protein kinase A). On electrophoresis, the hydrolysates of 32P-labeled lipomodulin showed a single radioactive spot, which comigrated with authentic phosphotyrosine. The partially purified middle-sized tumor antigen was able to phosphorylate lipomodulin after being phosphorylated by protein kinase C but not by the catalytic subunit of protein kinase A. Our findings suggest that the activity of a tyrosine-specific kinase, which phosphorylates lipomodulin in vivo as well as in vitro, is stimulated by protein kinase C and inhibited by protein kinase A.
当鼠胸腺细胞受到诸如刀豆球蛋白A、钙离子载体A23187或4β-佛波醇12-肉豆蔻酸酯13-乙酸酯等促有丝分裂原刺激时，可免疫沉淀的脂调素（一种磷脂酶抑制蛋白）中32P的掺入量显著增加。这些化合物增强了45Ca2+流入胸腺细胞，进而增加了蛋白质磷酸化，这可能是通过钙和磷脂依赖性蛋白激酶（蛋白激酶C）实现的。环8-溴-AMP是淋巴细胞有丝分裂的抑制剂，它阻断了促有丝分裂原刺激的脂调素磷酸化，尽管它通过环AMP依赖性激酶（蛋白激酶A）刺激蛋白质磷酸化。在电泳时，32P标记的脂调素水解产物显示出一个单一的放射性斑点，它与 authentic 磷酸酪氨酸迁移在一起。部分纯化的中等大小肿瘤抗原在被蛋白激酶C磷酸化后能够使脂调素磷酸化，但不能被蛋白激酶A的催化亚基磷酸化。我们的研究结果表明，一种酪氨酸特异性激酶的活性在体内和体外都能使脂调素磷酸化，它受到蛋白激酶C的刺激，并被蛋白激酶A抑制。
