两种酪氨酸蛋白激酶活性在主动脉平滑肌细胞增殖周期中的动态变化

THE DYNAMICS OF TWO TYPES OF TYROSINE PROTEIN KINASES IN THE PROLIFERATION OF CULTIVATED VASCULAR SMOOTH MUSCLE CELLS

本文以人工合成的多肽PGAT 为底物鉴定了培养的家兔ASMC 膜性TPK。发现Mg^(2+)和Mn^(2+)对ASMC 胞浆膜性TPK 和核膜性TPK 的激活作用有两点不同:(1)它们对前者的最适激活浓度高于后者;(2)对胞浆膜性TPK,Mn^(2+)最大激活效应大于Mg^(2+)而对核膜性TPK,Mn^(2+)则低于Mg^(2+)。这两种TPK活性在其G_1期的变化特点是:胞浆膜性TPK最高活性出现在G_1晚期(9 h),核膜性TPK最高活性则出现在G_1早期(3 h)。

We have studied the membrane-boundtyrosine protein kinases(TPK)in cultiva-ted aortic smooth muscle cells(ASMC)from the rabbit,and found that the cytoso-lic(membranous)TPK and the nuclear(membranous)TPK are two distinctive ty-pes of isozymes as judged by criteria ondynamics:(1)using synthetic poly(Glu.Ala.Tyr)_n(6∶3∶1)as a substrate,the rela-tive extents of stimulation by Mn^(2+)(450%)was more effective than that by Mg^(2+)(100%)on cytosolic TPK,but Mn^(2+)wasless effective(100%)than Mg^(2+)(130%)on nuclear TPK:(2)the concentrations ofMn^(2+)and Mg^(2+)giving maximal stimulationon cytosolic TPK were 15 mmol/L and 50mmol/L,whereas on nuclear TPK were 1mmol/L and 5 mmol/L,respectively.Theseresults indicate that the attitutes toward Mn^(2+)and Mg^(2+) can distinguish the cytosolic TPKfrom the nuclear one.In nucleus,with the entry of ASMCfrom G_0 to G_1 stage,TPK activity increasedrapidly and reached the peak(12 times G_0activity)at the early G_1 stage(3 hrs fromG_0),then decreased dramatically to basicline,and remained at a lower level there-after.In cytosol,the TPK activity decreasedwith the entry of ASMC from G_0 to G_1stage and reached its lowest point at themiddle of G_1 stage(6 hrs from G_0),andthen increased with a transient peak at thelate G_1 stage(9 hrs).It went down to G_0level before DNA synthesis.