Fisher Isaac J, Jenkins Meredith L, Tall Gregory G, Burke John E, Smrcka Alan V
Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA; Department of Pharmacology and Physiology, University of Rochester School of Medicine, Rochester, NY 14629, USA.
Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 2Y2, Canada.
Structure. 2020 Jul 7;28(7):810-819.e5. doi: 10.1016/j.str.2020.04.012. Epub 2020 May 12.
Phospholipase C (PLC) enzymes hydrolyze phosphoinositide lipids to inositol phosphates and diacylglycerol. Direct activation of PLCβ by Gα and/or Gβγ subunits mediates signaling by Gq and some Gi coupled G-protein-coupled receptors (GPCRs), respectively. PLCβ isoforms contain a unique C-terminal extension, consisting of proximal and distal C-terminal domains (CTDs) separated by a flexible linker. The structure of PLCβ3 bound to Gα is known, however, for both Gα and Gβγ; the mechanism for PLCβ activation on membranes is unknown. We examined PLCβ2 dynamics on membranes using hydrogen-deuterium exchange mass spectrometry (HDX-MS). Gβγ caused a robust increase in dynamics of the distal C-terminal domain (CTD). Gα showed decreased deuterium incorporation at the Gα binding site on PLCβ. In vitro Gβγ-dependent activation of PLC is inhibited by the distal CTD. The results suggest that disruption of autoinhibitory interactions with the CTD leads to increased PLCβ hydrolase activity.
磷脂酶C（PLC）可将磷酸肌醇脂质水解为肌醇磷酸和二酰基甘油。Gα和/或Gβγ亚基对PLCβ的直接激活分别介导了Gq和一些Gi偶联的G蛋白偶联受体（GPCR）的信号传导。PLCβ亚型包含一个独特的C末端延伸区，由近端和远端C末端结构域（CTD）组成，中间由一个柔性连接子隔开。已知与Gα结合的PLCβ3的结构，然而，对于Gα和Gβγ而言，PLCβ在膜上的激活机制尚不清楚。我们使用氢-氘交换质谱（HDX-MS）研究了膜上PLCβ2的动力学。Gβγ导致远端C末端结构域（CTD）的动力学显著增加。Gα在PLCβ上的Gα结合位点处的氘掺入减少。在体外，远端CTD可抑制Gβγ依赖的PLC激活。结果表明，与CTD的自抑制相互作用的破坏导致PLCβ水解酶活性增加。
