蛋白激酶C在大西洋鮭魚嗅覺訊息傳導中的角色

Role of Protein Kinase C in Olfactory Signal Transduction in Atlantic Salmon

本研究想探究大西洋鮭魚經由味道（odors）激活的嗅覺磷脂解酶C（PLC）之活性是否受蛋白激酶C（PKC）的調控？取2~3歲大西洋鮭魚的嗅覺器官並萃取其富含表皮細胞膜（PMR）的部份，並以此為蛋白激酶C及磷脂解酶C的來源。西方墨點定性分析及免疫組織化學（immunohistochemistry）定位均顯示蛋白激酶C存在並沿著嗅覺器官的表皮細胞。如果PMR先以蛋白激酶C的活化劑（PMA）和ATP或者okadaic acid處理，再以胺基酸激活磷脂解酶C的活性，結果顯示磷脂解酶C的活性均被蛋白激酶C抑制。如果PMR先以蛋白激酶C的抑制劑（staurosporine）或以不具活化蛋白激酶C活性PMA的類似物（PB）處理，磷脂解酶C的活性不會被抑制。磷酸化PMR，33kD的磷酸化蛋白質是蛋白激酶C的受質。總結以上結果，不管是在免疫分析或酵素分析上均顯示蛋白激酶C存在於大西洋鮭魚的嗅覺系統內，蛋白激酶C也許扮演著由味道所誘導出的一個嗅覺訊息傳導回饋抑制劑。

The hypothesis that Protein kinase C （PKC） might regulate the activation of olfactory phospholipase C （PLC） by odors was tested in this study. PKC was identified in olfactory rosettes from Atlantic salmon （Salmo salar） by immunoblotting and immunohistochemistry. PKC was preactivated in a plasma membrane rich （PMR） fraction with phorbol 12-myristate 13-acetate （PMA）, ATP and with or without okadaic acid （OkA） prior to activation of PLC with an odorant amino acid mixture （AA）. In each case, activation of PLC was suppressed. PKC activity presumably potentiated by inhibition of phosphoprotein phosphatase activity by okadaic acid. Staurosporine （Stsp） prevented this suppression of olfactory PLC activity and an inactive phorbol monoester （PB） had no effect on PLC activity. Numerous phosphoproteins were detected in the olfactory PMR fraction by autoradiography, of these, a 33 kDa phosphoprotein appeared to be a substrate of PKC. Immunological and enzymatic analyses indicate that PKC is present in the olfactory system of Atlantic salmon where PKC may serve as a feedback inhibitor of odor-induced signal transduction cascade.