Department of Biological Chemistry & Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA.
Department of Medicine, University of California, San Diego, San Diego, CA, USA.
Sci Adv. 2019 Oct 16;5(10):eaax8855. doi: 10.1126/sciadv.aax8855. eCollection 2019 Oct.
PIP-dependent Rac exchanger 1 (P-Rex1) is activated downstream of G protein-coupled receptors to promote neutrophil migration and metastasis. The structure of more than half of the enzyme and its regulatory G protein binding site are unknown. Our 3.2 Å cryo-EM structure of the P-Rex1-Gβγ complex reveals that the carboxyl-terminal half of P-Rex1 adopts a complex fold most similar to those of phosphoinositide phosphatases. Although catalytically inert, the domain coalesces with a DEP domain and two PDZ domains to form an extensive docking site for Gβγ. Hydrogen-deuterium exchange mass spectrometry suggests that Gβγ binding induces allosteric changes in P-Rex1, but functional assays indicate that membrane localization is also required for full activation. Thus, a multidomain assembly is key to the regulation of P-Rex1 by Gβγ and the formation of a membrane-localized scaffold optimized for recruitment of other signaling proteins such as PKA and PTEN.
依赖于 PIP 的 Rac 交换因子 1（P-Rex1）在 G 蛋白偶联受体下游被激活，以促进中性粒细胞的迁移和转移。该酶的一半以上结构及其调节 G 蛋白结合位点尚不清楚。我们解析的 P-Rex1-Gβγ 复合物的 3.2Å 冷冻电镜结构表明，P-Rex1 的羧基末端采用了一种与磷酸肌醇磷酸酶非常相似的复杂折叠。尽管没有催化活性，但该结构域与一个 DEP 结构域和两个 PDZ 结构域融合，形成了 Gβγ 的一个广泛的对接位点。氢氘交换质谱提示 Gβγ 结合诱导 P-Rex1 的别构变化，但功能测定表明膜定位对于完全激活也是必需的。因此，多结构域组装是 Gβγ 调节 P-Rex1 以及形成膜定位支架的关键，该支架优化了招募其他信号蛋白（如 PKA 和 PTEN）的能力。
