中文摘要：

出芽酵母（Saccharomyces cerevisiae）中的Ypk1与人体蛋白激酶SGK（Human serum- and glucocorticoid-inducible kinase）同源. Ypk1的504位苏氨酸残基是其激活环内的磷酸化位点，也称之为PDK1位点，而662位苏氨酸残基是位于其疏水区的PDK2位点，这两个位点的磷酸化对其激酶活性非常重要. 对Ypk1过量表达后其PDK1和PDK2位点的磷酸化调控研究结果显示，Ypk1过量表达后其PDK1和PDK2位点磷酸化水平在对数生长期呈现递增趋势，至平台期趋于稳定并在7 d的时序衰老过程中始终维持较高的磷酸化水平. 在野生型细胞中分别过量表达Ypk1T504A和Ypk1T662A两个突变体会导致细胞对渗透压胁迫敏感性增加. 而短暂渗透压胁迫处理会导致过量表达的Ypk1的PDK1和PDK2位点部分去磷酸化. 研究结果表明过量表达的Ypk1的PDK1和PDK2位点磷酸化在出芽酵母时序衰老及胁迫应答过程中发挥着重要作用. 图5 参16

英文摘要：

The budding yeast protein kinase Ypk1 is a homologue of mammalian protein kinase SGK （human serum- and inducible glucocorticoid-kinase）. Ypk1 involves in many physiological processes, including cell wall integrity, endocytosis, and sphingolipid synthesis regulation during membrane stress. The residue Thr504 is the phosphorylation site in the activation loop of Ypk1, also called PDK1 site, whereas the residue Thr662 is the phosphorylation site in the hydrophobic pocket, also called PDK2 site. These two sites are of importance to Ypk1 activity. This study mainly focused on how the phosphorylation of these two sites was regulated after Ypk1 overexpression. Our results showed that in exponential growth phase the phosphorylation level of PDK1 and PDK2 in overexpressed Ypk1 increased gradually, whereas it became stable when cells entered stationary phase. During the 7 days of chronological aging, PDK1 and PDK2 sites of overexpressed Ypk1 maintained a high phosphorylation level. Overexpression of variant Ypk1-T504A or Ypk1-T662A in BY4741 strain resulted in cells more sensitive to osmotic stress. Furthermore, transient osmotic stress treatment induced Ypk1 partial dephosphorylation. This study suggested that the phosphorylation of PDK1 and PDK2 sites in Ypk1 plays important regulatory roles during chronological aging and stress response. Fig 5, Ref 16