Activation of phospholipase C/Ca^<2+> system in thyroid cells and its physiological and pathological roles.

我们最近发现腺苷抑制TSH诱导的腺苷环化酶/cAMP系统的激活，而增强TSH诱导的大鼠甲状腺细胞磷脂酶C/Ca~(2+)&Gt~(2+)系统的激活。在甲状腺细胞中，除了去甲肾上腺素、乙酰胆碱和三磷酸腺苷外，1-磷酸鞘氨醇(SLP)和鞘氨醇磷脂(SPC)等溶鞘磷脂也被认为是一种有效的钙动员物质。在这项研究中，我们计划阐明磷脂酶C/Ca^&lt；2+&gt；系统在甲状腺细胞中的作用。我们获得了以下新的发现。(1)在人甲状腺细胞中，也证实了磷脂酶C/Ca~(2+)&Gt~(2+)系统是通过TSH和腺苷的相互作用来调节的。(2)为了阐明TSH和腺苷调节磷脂酶C活性的相互作用机制，我们利用体内细胞重组系统Cos-7，其中编码受体的cDNA、每个野生型G蛋白亚基和突变亚基。我们发现腺苷对TSH诱导的两种反应的修饰是由单一类型的Gi蛋白GI2或Gi3介导的；α亚基介导抑制AC和β亚基对磷脂酶C的激活。(3)在腺苷诱导磷脂酶C/Ca^&lt；2+&gt；系统激活的情况下，Grave‘s免疫球蛋白，因此建议将磷脂酶C/Ca^&lt；2+&gt；系统的检测应用于一种新的诊断Grave病的方法。(4)SLP和SPC调节甲状腺细胞磷脂酶C/Ca~(2+)&Gt~(2+)系统、H_2O_2的产生和细胞增殖等。因此，这些脂质介质被认为是这些细胞中的新型激动剂。

We have recently found that adenosine inhibits TSH-induced activation of adenylyl cyclase/cAMP system and enhances TSH-induced activation of phospholipase C/Ca^<2+> system in rat thyroid cells. In thyroid cells, in addition to norepinephrine, acetylcholine and ATP,lysosphingolipids such as sphingosine 1-phosphate (SlP) and sphingosylsphosphorylcholine (SPC) has also been suggested to be a potent Ca^<2+> mobilizer. In this study, we planned to clarify the roles of phospholipase C/Ca^<2+> system in thyroid cells. We obtained the following novel findings. (1) In human thyroid cells as well, it was demonstrated that phospholipase C/Ca^<2+> system was regulated through the cross-talk of TSH and adenosine. (2) To clarify the cross-talk mechanism by which TSH and adenosine regulate phospholipase C activity, we used in vivo Cos-7 cell reconstitution system, in which cDNAs encoding receptors, each wild type G-protein subunit and mutant subunit. We found that adenosine-induced modification of two TSH-induced responses were mediated by a single type of Gi protein, Gi2 or Gi3 ; alpha subunit mediates inhibition of AC and betagamma subunits activation of phospholipase C.(3) Grave's IgG in the presence of adenosine induced activation of phospholipase C/Ca^<2+> system, and hence it was suggested that the measurement of phospholipase C/Ca^<2+> system is applied for a novel diagnosis of Grave's disease. (4) SlP and SPC regulated phospholipase C/Ca^<2+> system, H_2O_2 generation, cell proliferation and so on in thyroid cells. Thus, these lipid mediators were suggested to be novel agonists in these cells.