酿酒酵母蛋白激酶Sch9的PDK1位点调控C末端磷酸化状态

PDK1 site of Saccharomyces cerevisiae protein kinase Sch9 regulates C terminal phosphorylation conditions

摘要:

酿酒酵母蛋白激酶Sch9（哺乳动物p70S6k1的同源物）作为AGC激酶家族中重要一员，参与细胞寿命、自噬、胁迫应答、细胞呼吸等诸多至关重要的细胞生理调控过程。Sch9上PDK1和PDK2两个磷酸化位点分别受到各自上游蛋白激酶对其磷酸化水平的调控并最终影响Sch9的活性，通过这种调控方式达到传递生物信号的目的。这里利用PDK1和PDK2位点点突变的两种突变体，分别进行生长、寿命表型检测及免疫印迹分析实验，发现PDK1位点的磷酸化水平对于Sch9活性起着主导性作用，并且PDK1位点发生去磷酸化会促进C末端高度磷酸化，而PDK1发生磷酸化会抑制C末端的磷酸化。由此说明Sch9上PDK1和PDK2位点是否发生磷酸化除了受到各自上游激酶的调节外，两者之间还存在着一种负调控机制。

Abstract:

As an important member of AGC (cAMP- and cGMP-dependent protein kinases and protein kinase C) family kinases，Saccharomyces cerevisiae protein kinase Sch9 (orthologue of mammalian protein kinase S6K1) participates in lots of cellular biological regulation processes such as lifespan, autophagy, stress response and cellular respiration.The phosphorylation levels of two main phosphorylation sites on Sch9,namely PDK1 site and PDK2 site,are regulated by protein kinases of their upstream and the alterant phosphorylation also changes Sch9 activity.In this way,Sch9 seems like a signal hinge to transfer biological signals.Using two mutants of point mutation of PDK1 and PDK2 sites,growth assay,chronological lifespan detection and western blotting were done.We demonstrated that phosphorylation at the PDK1 site is indispensable for Sch9 activity.In addition,dephosphorylation at PDK1 site can induce prominent phosphorylation at C terminal.On the contrary,phosphorylation of the PDK1 site depresses phosphorylation at C terminal.Thus,phosphorylation conditions of PDK1 and PDK2 site on Sch9 are not only regulated by theirself-upstream,but also influenced by a negative control mechanism existing in their interaction.