Galvin-Parton P A, Watkins D C, Malbon C C
Department of Pharmacology, State University of New York, Stony Brook 11794-8651.
J Biol Chem. 1990 Oct 15;265(29):17771-9.
F9 embryonal mouse teratocarcinoma cells were differentiated to a primitive endoderm-like phenotype by retinoic acid and to a parietal endoderm-like phenotype by retinoic acid in combination with dibutyryl cyclic AMP. The secretion of tissue plasminogen activator (tPA) is a characteristic of the cells displaying the differentiated phenotypes. The fundamental question of whether tPA secretion is regulated acutely by G-protein-mediated transmembrane signaling was explored. Cells differentiated to primitive and parietal endoderm demonstrated a rapid tPA response to stimulation by beta-adrenergic agonist (isoproterenol). Adenylyl cyclase activity in response to isoproterenol and GTP, but not forskolin, was greater in primitive and parietal endoderm than F9 stem cells. Both primitive and parietal endoderm cells, but not F9 stem cells, displayed beta-adrenergic stimulation of cyclic AMP accumulation. Retinoic acid induced F9 stem cells to the primitive endoderm phenotype and increased beta-adrenergic receptor levels 3-fold. Gi alpha 2 levels declined, G beta-subunits increased, and Gs alpha levels were unchanged following differentiation to primitive endoderm. In parietal endoderm cells beta-adrenergic receptors increased 2-fold over F9 stem cells, Gi alpha 2 levels declined even further than in primitive endoderm, G beta-subunits increased compared to F9 stem cells, and Gs alpha levels again were unchanged. The marked potentiation of short-term stimulation of tPA secretion in the differentiated state may be best explained by the retinoic acid-induced increase in expression of beta-adrenergic receptors coupled with a decline in Gi alpha 2 levels. Short-term regulation by G-protein-linked receptors represents a novel mode for the control of tPA secretion.
维甲酸可使F9胚胎小鼠畸胎瘤细胞分化为原始内胚层样表型，而维甲酸与二丁酰环磷酸腺苷联合使用可使其分化为滋养层内胚层样表型。组织纤溶酶原激活物（tPA）的分泌是显示分化表型细胞的一个特征。我们探讨了tPA分泌是否受G蛋白介导的跨膜信号急性调节这一基本问题。分化为原始内胚层和滋养层内胚层的细胞对β-肾上腺素能激动剂（异丙肾上腺素）刺激表现出快速的tPA反应。与F9干细胞相比，原始内胚层和滋养层内胚层对异丙肾上腺素和GTP（而非福斯高林）的腺苷酸环化酶活性更高。原始内胚层和滋养层内胚层细胞（而非F9干细胞）均表现出β-肾上腺素能刺激引起的环磷酸腺苷积累。维甲酸诱导F9干细胞分化为原始内胚层表型，并使β-肾上腺素能受体水平增加3倍。分化为原始内胚层后，Giα2水平下降，Gβ亚基增加，Gsα水平不变。与F9干细胞相比，滋养层内胚层细胞中的β-肾上腺素能受体增加了2倍，Giα2水平比原始内胚层下降得更明显，Gβ亚基增加，Gsα水平同样不变。在分化状态下，tPA分泌短期刺激的显著增强可能最好由维甲酸诱导的β-肾上腺素能受体表达增加以及Giα2水平下降来解释。G蛋白偶联受体的短期调节代表了一种控制tPA分泌的新模式。
