| Co-Investigator(Kenkyū-buntansha) |
SHO Kimie Gunma University, Institute for Mol.and Cell.Regul.Research Assistant, 生体調節研究所, 教務員 (40201561)
TOMURA Hideaki Gunma University, Institute for Mol.and Cell.Regul., Assistant, 生体調節研究所, 助手 (70217553)
OKAZIMA Fumikazu Gunma University, Institute for Mol.and Cell.Regel., Assistan Professor, 生体調節研究所, 助教授 (30142748)
KONDO Yoichi Gunma University, Institute for Mol.and Cell.Regul., Professor (70008598)
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| Research Abstract |
In the recent years, through experiments using recombinant TSH receptors, it has been shown that one kind of receptor molecule can activate both of the signal transduction systems, the cAMP system and the phospholipase (PLC) -Ca^<2+> system. On the other hand, we have found that adenosine (Ado) which is derived from ATP can change the flow of the information by affecting the effect of TSH as to enhancing the activation of PLC-Ca^<2+> system, and at thesame time inhibiting the activation of the cAMP system. In this study, such modulation mechanism of Ado on the effect of TSH has been analyzed by means of cellular and molecular biological methods. The results are as follows.
1) Proved that the TSH/Ado cooperation occurs inside one cell : By tracing the change of Ca^<2+> in a FRTL-5 thyroid cell using Digital Video Imaging, we showed that both TSH and Ado affect the same type of Ca^<2+> pools located at various regions inside one cell.
2) Discovery of a new target of the Ado-induced modulat
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in : When the cellular Ca^<2+> concentration was raised without using TSH,this increased Ca^<2+> activated PLA2.Ado enhanced this function of elevated Ca^<2+> as well. Therefore Ado can modulate themetabolic control system in two steps. One before the mobilization of Ca^<2+> and another after it.
3) Reconstruction of the TSH/Ado cooperation mechanism : We prepared a model cell by introducing AdoA_1 receptor cDNA together with either muscarinic M3 receptor cDNA or TSH receptor cDNA.The observed functions of the cells indicated that the enhancement of TSH reaction before and after the Ca^<2+> mobilizatios, and the inhibition of the activation of adenylate-cyclase by TSH,all occurs by kind of A_1 receptor.
4) The identihfication of a PLC subtype participating in the cooperation of TSH and Ado : Ado enhanced the TSH-induced activation of PLCBbeta subtype but did not betaFGF-induced activation of PLCgamma, suggesting that Ado effect is specific to the PLCbeta activation which the G protein participates in.
5) Ado enhances the hydrogen peroxide formation by TSH : TSH induces the formation of hydrogen peroxide in thyroid cells. This TSH effect is brought about through the Ca^<2+> signaling system, and PLA^2 participates in it as well. By enhancing the activations of PLC and A_2 in this signal transduction system, Ado enhances the hydrogen peroxide formation inducing effect of TSH. Less
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