Lee Min Jae, Tasaki Takafumi, Moroi Kayoko, An Jee Young, Kimura Sadao, Davydov Ilia V, Kwon Yong Tae
Center for Pharmacogenetics and Department of Pharmaceutical Sciences, University of Pittsburgh, 3501 Terrace Street, Pittsburgh, PA 15261, USA.
Proc Natl Acad Sci U S A. 2005 Oct 18;102(42):15030-5. doi: 10.1073/pnas.0507533102. Epub 2005 Oct 10.
The ATE1-encoded Arg-transferase mediates conjugation of Arg to N-terminal Asp, Glu, and Cys of certain eukaryotic proteins, yielding N-terminal Arg that can act as a degradation signal for the ubiquitin-dependent N-end rule pathway. We have previously shown that mouse ATE1-/- embryos die with defects in heart development and angiogenesis. Here, we report that the ATE1 Arg-transferase mediates the in vivo degradation of RGS4 and RGS5, which are negative regulators of specific G proteins whose functions include cardiac growth and angiogenesis. The proteolysis of these regulators of G protein signaling (RGS) proteins was perturbed either by hypoxia or in cells lacking ubiquitin ligases UBR1 and/or UBR2. Mutant RGS proteins in which the conserved Cys-2 residue could not become N-terminal were long-lived in vivo. We propose a model in which the sequential modifications of RGS4, RGS5, and RGS16 (N-terminal exposure of their Cys-2, its oxidation, and subsequent arginylation) act as a licensing mechanism in response to extracellular and intracellular signals before the targeting for proteolysis by UBR1 and UBR2. We also show that ATE1-/- embryos are impaired in the activation of extracellular signal-regulated kinase mitogen-activated protein kinases and in the expression of G protein-induced downstream effectors such as Jun, cyclin D1, and beta-myosin heavy chain. These results establish RGS4 and RGS5 as in vivo substrates of the mammalian N-end rule pathway and also suggest that the O2-ATE1-UBR1/UBR2 proteolytic circuit plays a role in RGS-regulated G protein signaling in the cardiovascular system.
由ATE1编码的精氨酸转移酶介导精氨酸与某些真核蛋白质的N端天冬氨酸、谷氨酸和半胱氨酸结合，产生N端精氨酸，其可作为泛素依赖性N端规则途径的降解信号。我们之前已经表明，小鼠ATE1基因敲除胚胎死于心脏发育和血管生成缺陷。在此，我们报告ATE1精氨酸转移酶介导RGS4和RGS5的体内降解，RGS4和RGS5是特定G蛋白的负调节因子，其功能包括心脏生长和血管生成。这些G蛋白信号调节（RGS）蛋白的蛋白水解在缺氧条件下或在缺乏泛素连接酶UBR1和/或UBR2的细胞中受到干扰。其中保守的半胱氨酸-2残基不能成为N端的突变RGS蛋白在体内寿命较长。我们提出了一个模型，其中RGS4、RGS5和RGS16的顺序修饰（其半胱氨酸-2的N端暴露、氧化以及随后的精氨酸化）在被UBR1和UBR2靶向蛋白水解之前，作为一种响应细胞外和细胞内信号的许可机制。我们还表明，ATE1基因敲除胚胎在细胞外信号调节激酶丝裂原活化蛋白激酶的激活以及G蛋白诱导的下游效应物如Jun、细胞周期蛋白D1和β-肌球蛋白重链的表达方面受损。这些结果确定RGS4和RGS5为哺乳动物N端规则途径的体内底物，也表明O2-ATE1-UBR1/UBR2蛋白水解回路在心血管系统中RGS调节的G蛋白信号传导中发挥作用。
