Gao P, Malbon C C
Department of Molecular Pharmacology, Diabetes and Metabolic Diseases Research Program, University Medical Center-HSC, State University of New York, Stony Brook, New York 11794-8651, USA.
J Biol Chem. 1996 Apr 12;271(15):9002-8. doi: 10.1074/jbc.271.15.9002.
The linkage between Gialpha2 and morphogen-induced promotion of F9 embryonic teratocarcinoma stem (F9 stem) cells to primitive endoderm was explored using probes of the mitogen-activated protein (MAP) kinase network. The morphogen-induced decline in Gialpha2 is shown to trigger activation of phospholipase C, thereby activating protein kinase C, MAP kinase, and cell progression to primitive endoderm. In the absence of retinoic acid, reduction-of-function mutants (Gialpha2-deficient) display the effects of morphogen, i.e. activation of phospholipase C, protein kinase C, MAP kinase, and progression to primitive endoderm. Gain-of-function mutants (expressing the Q205L activating-mutation of Gialpha2) displayed no activation of phospholipase C, protein kinase C, MAP kinase and no progression to primitive endoderm, even in the presence of retinoic acid. Selective inhibitors of protein kinase C, like the gain-of-function mutations, effectively block morphogen-induced progression to primitive endoderm. Morphogen triggers F9 stem cell progression by triggering Gialpha2 loss and thereby activation of downstream elements, including protein kinase C and MAP kinase.
利用丝裂原活化蛋白（MAP）激酶网络的探针，研究了Gialpha2与形态发生素诱导F9胚胎畸胎瘤干细胞向原始内胚层分化之间的联系。结果显示，形态发生素诱导的Gialpha2减少会触发磷脂酶C的激活，从而激活蛋白激酶C、MAP激酶，并使细胞向原始内胚层分化。在没有视黄酸的情况下，功能缺失突变体（Gialpha2缺陷型）表现出形态发生素的作用，即磷脂酶C、蛋白激酶C、MAP激酶的激活以及向原始内胚层的分化。功能获得突变体（表达Gialpha2的Q205L激活突变）即使在存在视黄酸的情况下，也未表现出磷脂酶C、蛋白激酶C、MAP激酶的激活，也未向原始内胚层分化。蛋白激酶C的选择性抑制剂与功能获得突变体一样，能有效阻断形态发生素诱导的向原始内胚层的分化。形态发生素通过触发Gialpha2的缺失，进而激活包括蛋白激酶C和MAP激酶在内的下游元件，从而触发F9干细胞的分化。
