Role of serum and glucocorticoid-regulated protein kinase (SGK) on insulin signaling pathway

1. 为了鉴定与SGK1相互作用的蛋白，我们利用人脑cDNA文库进行了两次杂交筛选。鉴定出具有两个PDZ结构域和磷酸酪氨酸结合结构域（PBD）的衔接蛋白Mint2。SGK1与存在于c端PDZ结构域相互作用，而不与n端PDZ结构域和PBD相互作用。通过过氧化氢（SGK1.2的激活剂之一）处理细胞，SGK1和Mint2蛋白的相互作用增加。SGK亚型参与K+通道调控ssgk1最初被确定为糖皮质激素敏感基因。随后，SGK1被证明可以激活包括K+通道在内的离子通道。最近有两个同源激酶SGK2和SGK3被克隆出来。为了阐明SGK亚型在K+通道调控中的作用，以及这些亚型的表达对肾上皮细胞电学特性的影响。转染SGK1、SGK2或SGK3后，电压门控的K+电流增加，表明三种SGK亚型对K+通道都有强烈的刺激作用。

1. Identification of SGK1 interacting proteinIn order to identify protein(s) which interact with SGK1, two hybrid screen was carried out using human brain cDNA library. Adaptor protein Mint2 which possesses two PDZ domains and phosphotyrosine binding domain (PBD) was identified. SGK1 interacted with PDZ domain which exists at C-terminal but not with N-terminal PDZ domain and PBD. The interaction of SGK1 and Mint2 proteins was increased by treatment of cells with hydrogen peroxide, one of the activator of SGK1.2. Involvement of SGK isoforms in regulation of K+ channelsSGK1 was originally identified as a glucocoticoid sensitive gene. Subsequently SGK1 was shown to activate ion channels including K+ channel. Recently two homologous kinases, SGK2 and SGK3 have been cloned. To elucidate the role of SGK isoforms on regulation of K+ channel, effect of expression of these isoforms on electrical properties of renal epithelial cells. Transfection of SGK1, SGK2 or SGK3 increased the voltage-gated K+ current indicating strong stimulating effect of all three isoforms of SGK on K.+ channels.