BPS2026 – Electrostatic interactions drive membrane association of PLCβ enzymes

PLCβ enzymes are canonical downstream targets of G protein-coupled receptor (GPCR) signaling via direct activation by the G proteins Gβγ and Gα q . Upon activation, PLCβ enzymes cleave PIP2 from the plasma membrane, producing IP3 and DAG, which elevate intracellular Ca 2+ and activate protein kinase C, respectively. PLCβ function is essential for a myriad of cellular processes, such as cardiac and neuronal function as well as macrophage activation. Accordingly, dysregulation of these enzymes leads to diseased states, including cancer and cardiac hypertrophy. PLCβ enzymes are unique in that they are aqueous-soluble but must first partition onto the membrane surface to access their lipid substrate. This property enables the dual regulation of their activity at both the catalytic step and partitioning step. Our recent work demonstrated that G proteins utilize both these mechanisms to activate PLCβs. Specifically, Gβγ activates by membrane recruitment and orientation and Gα q activates by increasing the catalytic rate constant. While membrane association is a crucial step of PLCβ activity with important regulatory roles, the underlying molecular mechanisms remain poorly understood. PLCβ membrane association involves direct interactions with phospholipids on the plasma membrane, suggesting that the chemical properties of phospholipids could influence this association. To address this question, we systematically tested the effects of phospholipid head group chemistry on PLCβ membrane association and demonstrate that anionic lipids are essential. We identified interactions between anionic phospholipids and basic residues in the distal c-terminal domain of PLCβ that are responsible for robust PLCβ partitioning. Finally, we show that Gβγ-dependent membrane association of PLCβ is also influenced by anionic lipids. Taken together, these findings support an updated model of PLCβ regulation where phospholipids and G proteins cooperate to fine-tune PLCβ activity, facilitating cellular signal transduction.