蛋白激脢之細胞訊息傳遞路徑中DARPP-32蛋白所扮演的角色---對大鼠學習記憶和抗細胞凋亡機制的影響

Abstract

蛋白激酶CK2是屬於一種serine/threonine類的蛋白激酶，CK2與抗細胞凋亡相關的議題已被廣泛探討，這些研究報告指出CK2可以經由活化Akt/PKB、NF-B和ARC蛋白（apoptosis repressor with caspase recruitment domain）等機制來促進細胞的存活。蛋白dopamine and cyclic AMP-regulated phosphoprotein, Mr. 32kDa（DARPP-32）最初是在紋狀體腦區中被發現的，主要受到來自多巴胺的刺激增加了細胞內cAMP的含量進而活化Protein kinase A對DARPP-32蛋白進行磷酸化作用，除此之外，細胞內其他一些激酶如CK2、CK1和Cdk5也會對DARPP-32進行磷酸化作用，近年來的研究指出DARPP-32除了與藥物成癮的生理現象有關外，應該還參與在其他生理調控或改變的機制之中，諸如：DARPP-32和其isoform tDARPP也在腸胃癌細胞內被發現有較高的表現量而且可以減緩癌細胞的死亡，因此DARPP-32也有參與在抗細胞凋亡機制之中的可能性。由於DARPP-32是CK2磷酸化作用的其中一個受質，而我們最近的研究也發現CK2參與在BDNF抗細胞凋亡的機制之中，承續這個研究結果，本研究計畫今年度的研究重點在確立CK2/DARPP-32/Bcl-xL訊息傳遞路徑的相關性和調控CK2活性或DARPP-32表現是否可拮抗興奮性神經毒性物質對神經細胞的傷害。

Protein kinase CK2 is a multifunctional and ubiquitous serine/threonine protein kinase. Many studies of CK2 are focused on its anti-apoptotic effects. There are many reports showing that CK2 could activate protein kinase Akt, NF-B and ARC protein (apoptosis repressor with caspase recruitment domain) and to enhance cell survival. Meanwhile, the dopamine and cyclic AMP-regulated phosphoprotein, Mr. 32kDa (DARPP-32) was originally found to be activated by dopamine and cAMP through PKA-dependent phosphorylation in the striatum. DARPP-32 was also found to be phosphorylated by other kinase such as CK2, Ck1 and Cdk5. Beside it well-known role in drug addiction, recent studies indicated that DARPP-32 might also involve in other physiological functions. The higher protein expression of DARPP-32 and its isoform tDARPP were found in the gastrointestinal carcinomas and were relative to maintain the cell survival. In our past study, we found that CK2 activation was involved in the anti-apoptotic effects of BDNF in the recent study. Since the DARPP-32 is one of substrates for CK2 phosphorylation, the present study is aimed to investigate the role of and mechanism of DARPP-32 involved in the CK2-mediated signaling pathway. The specific aims of this year are as following: (1) to investigate whether the relationships between CK2, DARPP-32 and Bcl-xL exist in the hippocampal CA1 regions of rats in the anti-apoptotic mechanism; (2) to clarify whether manipulation of CK2 activity and DARPP-32 phosphorylation status will influence the anti-apoptotic effects against excitotoxicity.