PLCG2

Phospholipase C Gamma 2 (PLCG2) is a critical signaling enzyme uniquely enriched in microglia within the central nervous system. It functions as the direct downstream effector for TREM2 and other ITAM-containing receptors, acting as the key transducer that converts membrane receptor activation into intracellular calcium mobilization.

Upon TREM2-TYROBP activation, SYK phosphorylates PLCG2, which then cleaves PIP2 into IP3 and DAG. This immediately triggers the release of calcium from the endoplasmic reticulum, an event strictly required for driving microglial phagocytosis, chemotaxis, and the transcriptional shift into the Disease-Associated Microglia (DAM) state.

A rare coding variant in PLCG2 (P522R) was discovered to uniquely protect against Alzheimer's disease. This hypermorphic (gain-of-function) mutation slightly enhances the enzyme's baseline activity, allowing microglia to respond more robustly to pathological insults without becoming hyper-inflammatory. Conversely, loss-of-function variants lock microglia in a homeostatic or stalled state, entirely preventing their ability to corral amyloid plaques, cementing PLCG2 as a high-value target for pharmacological agonism to enhance neuroprotective clearance.