Rho5p is involved in mediating the osmotic stress response in Saccharomyces cerevisiae, and its activity is regulated via Msi1p and Npr1p by phosphorylation and ubiquitination
Rho5p is involved in mediating the osmotic stress response in Saccharomyces cerevisiae, and its activity is regulated via Msi1p and Npr1p by phosphorylation and ubiquitination
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DOI：
10.1128/ec.00120-08
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发表时间：
2008-09-01
期刊：
影响因子：
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通讯作者：
Thomas, David Y.
中科院分区：
文献类型：
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作者：
Annan, Robert B.;Wu, Cunle;Thomas, David Y.
Rho家族的小GTP酶充当分子开关，并且Rho蛋白的GTP结合状态的调节是在体内调节其信号传导活性的充分表征的手段。相比之下，Rho型GTP酶通过翻译后修饰的调节知之甚少。在这里，我们提出的证据的控制酿酒酵母Rho型GTTRYPRho 5 p的磷酸化和泛素化。Rho 5 p与Ste 50 p结合，在渗透胁迫条件下，Delta ste 50菌株中激活的Rho 5（Q91 H）等位基因的表达是致命的。过表达筛选确定RGD 2和MSI 1是这种致死性的渗透敏感性的高拷贝抑制因子。Rgd 2 p已被确定为是一个可能的Rho 5 p GTP酶激活蛋白的基础上，在体外测定;这一结果支持其作为一个调节剂的Rho 5 p活性在体内的功能。MSI 1先前被鉴定为过度活跃的Ras/环AMP信号传导的抑制剂，其中它拮抗Npr 1 p激酶活性并促进泛素化。在这里，我们表明Msi 1 p也通过Npr 1 p抑制激活的Rho 5 p信号传导。Rho 5 p是泛素化的，其表达在蛋白酶体活性受损的菌株中是致命的。这些数据确定Rho 5 p作为Msi 1 p/Npr 1 p调节的靶点，并描述了涉及磷酸化和泛素化的调节回路。
Small GTPases of the Rho family act as molecular switches, and modulation of the GTP-bound state of Rho proteins is a well-characterized means of regulating their signaling activity in vivo. In contrast, the regulation of Rho-type GTPases by posttranslational modifications is poorly understood. Here, we present evidence of the control of the Saccharomyces cerevisiae Rho-type GTPase Rho5p by phosphorylation and ubiquitination. Rho5p binds to Ste50p, and the expression of the activated RHO5( Q91H) allele in an Delta ste50 strain is lethal under conditions of osmotic stress. An overexpression screen identified RGD2 and MSI1 as being high-copy suppressors of the osmotic sensitivity of this lethality. Rgd2p had been identified as being a possible Rho5p GTPase-activating protein based on an in vitro assay; this result supports its function as a regulator of Rho5p activity in vivo. MSI1 was previously identified as being a suppressor of hyperactive Ras/cyclic AMP signaling, where it antagonizes Npr1p kinase activity and promotes ubiquitination. Here, we show that Msi1p also acts via Npr1p to suppress activated Rho5p signaling. Rho5p is ubiquitinated, and its expression is lethal in a strain that is compromised for proteasome activity. These data identify Rho5p as being a target of Msi1p/Npr1p regulation and describe a regulatory circuit involving phosphorylation and ubiquitination.