The phospholipase PLC-gamma is an important mediator of TCR, FCERI and DAP12 signal transduction. PLC-gamma hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) to produce inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG) and in-turn promotes the Ca+2 influx and activation of NFAT. Activation of PLC-gamma1 entails the binding of PLC-gamma1 to both LAT and SLP-76 adapter proteins. The amino-terminal SH2 domain of PLC-gamma1 was shown to preferentially bind phosphorylated LAT Y132 with high affinity and no detectable binding to phosphorylated tyrosines 171, 191, and 226. PLC-gamma1 was also shown to bind the adapter protein SLP-76 indirectly through GADS, which is bound to LAT at Y171 and Y191. SH3 domain of PLC-gamma1 associates with the proline-rich region of SLP-76 (Yablonski et al. 2001). PLC-gamma1 associates with Gads/SLP-76 complex before binding to p-Y132 of LAT (Houtman et al. 2005). PLC-gamma1 association with LAT is stabilized by Gads/SLP-76 bound to LAT (Zhu et al.2003). Association of PLC-gamma to LAT and SLP-76 couples it to the kinases (Syk and Tec family kinase) required for tyrosine phosphorylation and activation of PLC-gamma.
Mast cells express both PLC-gamma1 and PLC-gamma2 isoforms, which are phosphorylated by BTK/ITK and/or SYK. FCERI-dependent Ca2+ release requires the recruitment of PLC-gamma by SLP-76 and LAT. In mast cells, increased intracellular calcium triggers rapid release of preformed mediators, through a process of vesicle exocytosis, known as degranulation.
Recruitment and activation of phospholipase C gamma (PLC-gamma) is involved in DAP12 signal transduction. Phosphorylation of multiple substrates including PLC-gamma1 has been observed in Ly49D/DAP12 triggered NK cells (McVicar et al. 1998). In myeloid cells, PLC-gamma2 is recruited and then phosphorylated upon activation of TREM2 and DAP12 (Peng et al. 2010).