Prakash Ajit, Li Zijian, Chirasani Venkata R, Rasquinha Juhi A, Valentin Natalie H, Hubbard Garrett B, Yin Guowei, Dohlman Henrik G, Campbell Sharon L
Department of Biochemistry & Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Res Sq. 2024 Apr 30:rs.3.rs-4203924. doi: 10.21203/rs.3.rs-4203924/v1.
Heterotrimeric G proteins (Gα, Gβ and Gγ) act downstream of G-protein-coupled receptors (GPCRs) to mediate signaling pathways that regulate various physiological processes and human disease conditions. Previously, human Gαi and its yeast homolog Gpa1 have been reported to function as intracellular pH sensors, yet the pH sensing capabilities of Gαi and the underlying mechanism remain to be established. Herein, we identify a pH sensing network within Gαi, and evaluate the consequences of pH modulation on the structure and stability of the G-protein. We find that changes over the physiological pH range significantly alter the structure and stability of Gαi-GDP, with the protein undergoing a disorder-to-order transition as the pH is raised from 6.8 to 7.5. Further, we find that modulation of intracellular pH in HEK293 cells regulates Gαi-Gβγ release. Identification of key residues in the pH-sensing network allowed the generation of low pH mimetics that attenuate Gαi-Gβγ release. Our findings, taken together, indicate that pH-dependent structural changes in Gαi alter the agonist-mediated Gβγ dissociation necessary for proper signaling.
异源三聚体G蛋白(Gα、Gβ和Gγ)在G蛋白偶联受体(GPCR)下游发挥作用,介导调节各种生理过程和人类疾病状态的信号通路。此前,已有报道称人类Gαi及其酵母同源物Gpa1可作为细胞内pH传感器,但Gαi的pH传感能力及其潜在机制仍有待确定。在此,我们在Gαi中识别出一个pH传感网络,并评估pH调节对G蛋白结构和稳定性的影响。我们发现,在生理pH范围内的变化会显著改变Gαi-GDP的结构和稳定性,随着pH从6.8升高到7.5,该蛋白会经历从无序到有序的转变。此外,我们发现调节HEK293细胞内的pH可调节Gαi-Gβγ的释放。在pH传感网络中鉴定关键残基使得能够产生减弱Gαi-Gβγ释放的低pH模拟物。综合我们的研究结果表明,Gαi中依赖于pH的结构变化会改变激动剂介导的Gβγ解离,而这对于正常信号传导是必需的。