Decoding the phosphorylation bar code in Arabidopsis G Biased Signaling

激素和神经递质调节细胞生长和生长中的各种生理过程 行为。它们的同源细胞表面受体有七个跨膜区，通过偶联作用。 到G蛋白，促进GDP的解离和随后的GTP的负载。信号减弱 当GTP被水解时，G信号蛋白的调节器会加速GTP酶的活性 GTP酶促进蛋白(GAP)活性。最近，我们发现了一种自然发生的7TM-RGS 拟南芥中的蛋白质(AtRGS1)，是葡萄糖或核苷酸-糖受体。它是一款 受体间隙。我们还发现，拟南芥Gα亚基(AtGPA1)具有快速的核苷酸交换 使核苷酸水解成为限速步骤。这一特性与慢速特性形成鲜明对比。 所有被测试的Gα亚基的核苷酸交换性质，其中Gdp的释放是 G蛋白周期。与动物不同，G蛋白周期的调节是在GTP水解步骤和 由AtRGS1调制。这种调节水平是由AtRGS1的可逆磷酸化控制的 和AtGPA1在这里被指定为集合的一组几乎未被破译的磷酸化氨基酸 磷化条形码。我们知道AtRGS1上的一种磷酸化模式是必要和充分的 启动AtRGS1内吞作用和在AtGPA1上启动另一种内吞作用会改变依赖AtRGS1的G周期的速率。 血浆中存在不同的AtRGS1/G蛋白/激酶/磷酸酶复合体 膜和这些不同的簇被不同的激动剂激活。此外，我们假设 最初的集群，集群中蛋白质的分类，以及随后的 激活后的集群组件由磷化条形码加密。利用一种基因的力量 系统将使我们能够确定条形码在多细胞环境中的生理作用。两者都有 我们将采用假设和发现驱动的方法来准确确定结构所赋予的是什么 监管控制。到目前为止，我们对拟南芥G蛋白周期的研究已经说明了G蛋白是如何 可以通过不同于传统全球环境基金的机制来调节周期。因此，更大程度的 现在人们认识到了周期的可塑性，并揭示了监管的新切入点。理解 这些新机制背后的结构将为调节其他G蛋白提供新的手段 循环。了解AtRGS1如何以配体依赖的方式调节G蛋白周期 为通过药物疗法调节G蛋白循环提供了新的可能性。的核心要素 异三聚体G蛋白偶联信号在真核生物中是保守的，但调节G蛋白偶联信号的机制 G蛋白的活性状态不是。这种变异，在基因编码的生物体中有同样大的差异 作为16亿年的进化，代表了G蛋白信号系统的全方位可塑性。 了解这种可塑性将揭示调节人类G信号的新方法。

Hormones and neurotransmitters modulate a variety of physiological processes in cell growth and behavior. Their cognate cell surface receptors, which have seven transmembrane domains, act by coupling to G proteins, promoting the dissociation of GDP and the subsequent loading of GTP. Signaling abates when GTP is hydrolyzed and GTPase activity is accelerated by Regulators of G Signaling proteins having GTPase accelerating protein (GAP) activity. Recently, we discovered a naturally-occurring 7TM-RGS protein in Arabidopsis (AtRGS1) that is a glucose or nucleotide-sugar receptor. It is the prototype of a receptor-GAP. We also showed that the Arabidopsis Gα subunit (AtGPA1) has rapid nucleotide exchange making nucleotide hydrolysis the rate limiting step. This property is in marked contrast to the slow nucleotide exchange property of all tested Gα subunits where GDP release is the rate limiting step of the G protein cycle. In contrast to animals, regulation of the G protein cycle is at the GTP hydrolysis step and is modulated by AtRGS1. This level of modulation is controlled by reversible phosphorylation of AtRGS1 and AtGPA1 at a mostly undeciphered set of phosphorylated amino acids designated here as the collective phospho-bar code. We do know that one phosphorylation pattern on AtRGS1 is necessary and sufficient to initiate AtRGS1 endocytosis and another on AtGPA1 changes the rate of AtRGS1-dependent G cycling. There are different clusters of complexes of the AtRGS1/G protein/kinase/phosphatase on the plasma membrane and these different clusters are activated by different agonists. Furthermore, we hypothesize that this initial clustering, the assortment of proteins in the cluster, and the subsequent trafficking of the cluster components after activation is encrypted by the phospho-bar code. Using the power of a genetic system will enable us to determine the physiological role of the bar code in a multicellular context. Both hypothesis- and discovery-driven approaches will be taken to determine precisely what structure imparts regulatory control. Our studies of the Arabidopsis G protein cycle have to date illustrated how the G-protein cycle can be regulated by mechanisms distinct from the classical GEF. Consequently, a greater degree of plasticity of the cycle is now appreciated and new entry points for regulation are revealed. Understanding the structure underlying these new mechanisms will provide a new means to regulate other G protein cycles. Understanding how AtRGS1 modulates the G protein cycle in a ligand-dependent manner opens up new possibilities to regulate G protein cycles through drug therapies. The core elements of heterotrimeric G protein coupled signaling are conserved in eukaryotes but the mechanism to regulate the active state of the G protein is not. This variation, genetically encoded in organisms divergent by as much as 1.6 billion years of evolution, represents the full range of plasticity of the G protein signaling system. Understanding this plasticity will reveal novel ways to regulate G signaling in humans.