An integrated mechanism of regulation of PLCβ enzymes

• 成果类型: Article
• 署名作者: Senarath, Kanishka; Fisher, Isaac J.; Jang, Wonjo; Lu, Sumin; Inoue, Asuka; Kostenis, Evi; Lyon, Angeline M.; Lambert, Nevin A.
• 署名单位: University System of Georgia; Augusta University; Purdue University System; Purdue University; Tohoku University; Kyoto University; University of Bonn; Purdue University System; Purdue University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-10575
• DOI: 10.1073/pnas.2500318122
• 发表日期: 2025-04-22
• 关键词: phospholipase-c-beta; coupled receptor kinase; membrane-binding; terminal region; gamma; activation; alpha; g-alpha(q); proteins; subunits

摘要

Phospholipase C beta (PLC beta) enzymes are the principal effectors activated by Gq heterotrimers. Both G alpha q and G beta gamma subunits can activate PLC beta, which requires precise positioning of PLC beta at the plasma membrane to relieve structural autoinhibition and give the active site access to the phosphatidylinositol 4,5-bisphosphate (PIP2) substrate. PLC beta enzymes possess a unique distal C-terminal domain (dCTD) that is critical for activation by G alpha q, but the reason for this is unclear. It is also not known how G protein activation affects the subcellular localization of PLC beta enzymes, some of which are found primarily in the cytosol despite needing to act at the plasma membrane. Here, we use bioluminescence spectroscopy, imaging, and gene editing to study the membrane disposition of PLC beta enzymes in living cells and to define the functional roles of the dCTD. We find that PLC beta translocates to the plasma membrane upon Gq activation, primarily by binding to G alpha q subunits. This is rapidly counteracted by PIP2 hydrolysis, which promotes PLC beta translocation back into the cytosol. PLC beta translocation and activation require binding of G alpha q to the catalytic domain and the dCTD at two distinct interfaces. G alpha q binding to the dCTD is required for activation even when PLC beta is artificially tethered to the plasma membrane, suggesting that this domain has functions beyond simply recruiting the enzyme to the PIP2 substrate. We propose that in addition to associating PLC beta with the plasma membrane, the dCTD reorders the alpha N helix of active G alpha q and thus participates directly in the precise positioning of the catalytic domain.