Involvement of Serum and Glucocorticoid Inducible Kinase 1 (SGK1) in VSMC Profile

描述（由申请人提供）：SGK 1是一种诱导型丝氨酸/苏氨酸激酶，参与上皮细胞的膜转运过程。研究表明，SGK 1是转录诱导的，并受到刺激依赖性的翻译后磷酸化。SGK 1的过度磷酸化导致其激酶活性的活化，并与细胞增殖、存活和细胞内离子和转运过程的变化有关。磷酸化还控制SGK 1的核/胞质穿梭，使得丝氨酸/苏氨酸残基上的过度磷酸化导致从胞质溶胶的核易位。尽管关于SGK 1在上皮细胞生物学中的作用已经取得了很大进展，但其在血管平滑肌细胞功能中的作用，特别是在病变形成的发展中的作用是完全未知的。因此，本申请试图定义SGK 1在调节血管平滑肌细胞命运中的作用，特别是当它涉及生长时。在初步研究中，我们发现，有效的促分裂剂，PDGF，显着和短暂的增加血管平滑肌细胞中的SGK 1 mRNA的表达，暗示这种激酶在血管平滑肌细胞生长的作用。我们还发现PDGF刺激与SGK 1磷酸化增加相关，表明PDGF可能介导SGK 1激酶活性的激活。有趣的是，受损颈动脉的免疫组织化学染色显示，SGK 1在新生内膜血管病变中上调。 根据这些发现，我们假设SGK 1是血管平滑肌细胞增殖的重要介质，其表达和/或活性的改变导致随后血管新生内膜病变形成的发展。我们将从以下几个方面来验证这一假说：（1）研究促有丝分裂刺激对体外培养的VSMC中SGK 1表达、活性和区室化的影响;（2）研究组成性SGK 1敲低和过表达对体外培养的VSMC生长调节的影响;（3）在大鼠颈总动脉球囊损伤模型中，观察机械性血管损伤对SGK 1表达和活性的影响。总的来说，这一系列的实验将深入了解SGK 1在血管平滑肌细胞增殖中的作用，并为未来的研究提供基础，以确定SGK 1在病理性血管重塑中的作用。最终，这些研究将SGK 1确定为动脉粥样硬化、再狭窄或高血压导致的闭塞性血管疾病的新治疗靶点。

DESCRIPTION (provided by applicant): SGK1 is an inducible serine/threonine kinase that has been implicated in membrane transport processes in epithelial cell. Studies have shown that SGK1 is transcriptionally induced and subject to stimulus-dependent post-translational phosphorylation. Hyperphosphorylation of SGK1 leads to activation of its kinase activity and has been linked to changes in cellular proliferation, survival and intracellular ion and transport processes. Phosphorylation also controls nuclear/cytoplasmic shuttling of SGK1 such that hyperphosphorylation on serine/threonine residues leads to nuclear translocation from the cytosol. Although much progress has been made regarding the role of SGK1 in epithelial cell biology, its role in vascular smooth muscle cell function and in the development of lesion formation in particular is completely unknown. Therefore, this application seeks to define the role of SGK1 in regulation of vascular smooth muscle cell fate, specifically as it relates to growth. In preliminary studies we found that the potent mitogen, PDGF, dramatically and transiently increases SGK1 mRNA expression in vascular smooth muscle cells implicating a role for this kinase in vascular smooth muscle cell growth. We also found that PDGF stimulation is associated with increased phosphorylation of SGK1, suggesting that PDGF may mediate activation of SGK1 kinase activity. Interestingly, immunohistological staining of injured carotid artery revealed that SGK1 is up-regulated in neointimal vascular lesions. In light of these findings, we hypothesize that SGK1 is an important mediator of vascular smooth muscle cell proliferation and that alterations in its expression and/or activity leads to the subsequent development of vascular neointimal lesion formation. We will test this hypothesis in the following aims: (1) to investigate the effects of mitogenic stimuli on SGK1 expression, activity and compartmentalization in VSMC in vitro; (2) to investigate the effect of constitutive SGK1 knockdown and over-expression on regulation of VSMC growth in vitro; (3) to investigate the effect of mechanical vascular injury on SGK1 expression and activity in a rat carotid artery balloon-injury model in vivo. Overall, this series of experiments will provide insight into the role of SGK1 in vascular smooth muscle cell proliferation and provide the basis for future studies to define the role of SGK1 in pathological vascular remodeling. Ultimately, these studies identify SGK1 as a novel therapeutic target for occlusive vascular diseases that occur as a consequence of atherosclerosis, restenosis or hypertension.