EF-hand motif found in phosphoinositide phospholipase C beta 3 (PI-PLC-beta3)
PI-PLC-beta3, also termed 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase beta-3, or phospholipase C-beta-3 (PLC-beta3), is widely expressed at highest levels in brain, liver, and parotid gland. It is activated by the heterotrimeric G protein alpha q subunits through their C2 domain and long C-terminal extension. It is also activated by the beta-gamma subunits of heterotrimeric G proteins. PI-PLC-beta3 associates with CXC chemokine receptor 2 (CXCR2) and Na+/H+ exchanger regulatory factor-1 (NHERF1) to form macromolecular complexes at the plasma membrane of pancreatic cancer cells, which functionally couple chemokine signaling to PI-PLC-beta3-mediated signaling cascade. Moreover, PI-PLC-beta3 directly interacts with the M3 muscarinic receptor (M3R), a prototypical G alpha-q-coupled receptor that promotes PI-PLC-beta3 localization to the plasma membrane. This binding can alter G alpha-q-dependent PLC activation. Furthermore, PI-PLC-beta3 inhibits the proliferation of hematopoietic stem cells (HSCs) and myeloid cells through the interaction of SH2-domain-containing protein phosphatase 1 (SHP-1) and signal transducer and activator of transcription 5 (Stat5), and the augment of the dephosphorylating activity of SHP-1 toward Stat5, leading to the inactivation of Stat5. It is also involved in atopic dermatitis (AD) pathogenesis via regulating the expression of periostin in fibroblasts and thymic stromal lymphopoietin (TSLP) in keratinocytes. In addition, PI-PLC-beta3 mediates the thrombin-induced Ca2+ response in glial cells. PI-PLC-beta3 contains a core set of domains, including an N-terminal pleckstrin homology (PH) domain, four atypical EF-hand motifs, a PLC catalytic core, and a single C2 domain. Besides, it has a unique C-terminal coiled-coil (CT) domain necessary for homodimerization. The PLC catalytic core domain is a TIM barrel with two highly conserved regions (X and Y) split by a highly degenerate linker sequence.