Structure and Function of Vps15 in the Endosomal G Protein Signaling Pathway
Structure and Function of Vps15 in the Endosomal G Protein Signaling Pathway
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DOI：
10.1021/bi900621w
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发表时间：
2009-07-14
期刊：
影响因子：
2.9
通讯作者：
Dohlman, Henrik G.
中科院分区：
文献类型：
--
作者：
Heenan, Erin J.;Vanhooke, Janeen L.;Dohlman, Henrik G.
G蛋白偶联受体介导细胞对各种刺激的反应，包括味觉、光和神经递质。在酿酒酵母中，信息素途径的激活触发导致交配的事件。长期以来，人们一直认为G蛋白介导的信号主要发生在质膜上。最近，已经表明G蛋白α亚基G-pal可以促进内体的信号传导，并且需要酵母中唯一的磷脂酰肌醇-3-激酶的两种组分，Vps 15和Vps 34。Vps 15含有多个WD重复序列，并且在GDP结合状态下优先与Gpa 1结合;这些观察结果使我们假设Vps 15可能在内体处起G蛋白β亚基的作用。在这里，我们展示了一个X射线晶体结构的Vps 15 WD域，揭示了一个七叶螺旋桨类似于典型的G β亚基。我们进一步表明，WD结构域是足以结合Gpa 1以及Atg 14，一个潜在的G γ蛋白，存在于一个复杂的Vps 15。Vps 15激酶结构域与中间结构域（连接激酶和WD结构域）一起也有助于Gpa 1结合，并且是Vps 15维持G蛋白信号传导所必需的。这些发现揭示了Vps 15 G β样结构域作为组装Gpa 1和Atg 14的支架，而激酶和中间结构域是内体适当信号传导所必需的。
G protein-coupled receptors mediate cellular responses to a wide variety of stimuli, including taste, light, and neurotransmitters. In the yeast Saccharomyces cerevisiae, activation of the pheromone pathway triggers events leading to mating. The view had long been held that the G protein-mediated signal occurs principally at the plasma membrane. Recently, it has been shown that the G protein alpha subunit G-pal can promote signaling at endosomes and requires two components of the sole phosphatidylinositol-3-kinase in yeast, Vps15 and Vps34. Vps15 contains multiple WD repeats and also binds to Gpa1 preferentially in the GDP-bound state; these observations led us to hypothesize that Vps15 may function as a G protein beta subunit at the endosome. Here we show an X-ray crystal structure of the Vps15 WD domain that reveals a seven-bladed propeller resembling that of typical G beta subunits. We show further that the WD domain is sufficient to bind Gpa1 as well as to Atg14, a potential G gamma protein that exists in a complex with Vps15. The Vps15 kinase domain together with the intermediate domain (linking the kinase and WD domains) also contributes to Gpa1 binding and is necessary for Vps15 to sustain G protein signaling. These findings reveal that the Vps15 G beta-like domain serves as a scaffold to assemble Gpa1 and Atg14, whereas the kinase and intermediate domains are required for proper signaling at the endosome.