Abstract
老鼠腎上腺腫瘤 (Rat Pheochromocytoma) PC12 細胞，在正常培養狀態之下，利用激脢活化因子/肝醣合成脢激脢-3 alpha(Glycogen SynthaseKinase-3 alpha，簡稱 GSK-3 alpha) 的抗體作免疫沉澱實驗,發現激脢FA/GSK-3 alpha 會因神經生長因子(nerve growth factor，簡稱 NGF)的作用而增加。若將此 PC12 細胞長時間培養於缺乏血清(serum-free)的培養液中，則激脢 FA/GSK-3 alpha 的活性將會下降。NGF 則可回復此種因缺乏血清之培養所造成的激脢 FA/GSK-3 alpha 活性下降。利用西方點墨法 (Western Blotting) 的實驗證明，上述實驗所造成的激脢 FA/GSK-3alpha 活性變化與 PC12 細胞內該酵素的蛋白質合成無關。 進一步以磷酸胺基酸分析 (Phosphoamino Acid Analysis，簡稱 PAA) 的技術，發現在上述實驗中造成激脢 FA/GSK-3 alpha 的活性變化主要乃根源於胳胺酸磷酸化 (tyrosine phosphorylation) 狀態的改變。吾人更由加入胳胺酸脢抑制劑 (tyrosine kinase inhibitor，Genistein) 的實驗證明：激脢 FA /GSK-3 alpha 參與由 NGF所調節的訊號傳遞過程(signaltransduction)乃透過胳胺酸磷酸化 (tyrosine phosphorylation) 來完成。Using immunoprecipitation and kinase assay, we found that nervegrowth factor (NGF) can stimulate upon kinase FA/GSK-3 alphaactivity in rat pheochromocytoma PC12 cells under normallycultured condition. Kinase FA/GSK-3 alpha activity decreasedwhen PC12 cells were cultured under a serum-starved condition.Nerve growth factor added into these serum-free culturesrestored the activity of kinase GSK-3 alpha declined by serumstarvation From Western Blotting, it has been proved that nochange on the protein synthesis level of kinase FA/GSK-3 alphacaused by either serum-free cultured or normally cultured PC12cells stimulated by NGF. Further investigation by phosphoaminoacid analysis, it's shown that the activity change of kinase FA/GSK-3 alpha is due to the phosphorylation state of tyrosineresidue on kinase FA/GSK-3 alpha. These data indicate thatkinase FA/GSK-3 alpha is involved in NGF-induced signaltransduction pathway through tyrosine phos- phorylation thatmight be different from MAPK-involved cascade.