EF-hand motif found in phosphoinositide phospholipase C beta 1 (PI-PLC-beta1)
PI-PLC-beta1, also termed 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase beta-1, or PLC-154, or phospholipase C-I (PLC-I), or phospholipase C-beta-1 (PLC-beta1), is expressed at highest levels in specific regions of the brain, as well as in the cardiovascular system. It has two splice variants, PI-PLC-beta1a and PI-PLC-beta1b, both of which are present within the nucleus. Nuclear PI-PLC-beta1 is a key molecule for nuclear inositide signaling, where it plays a role in cell cycle progression, proliferation and differentiation. It also contributes to generate cell-specific Ca2+ signals evoked by G protein-coupled receptor stimulation. PI-PLC-beta1 acts as an effector and a GTPase activating protein (GAP) specifically activated by the heterotrimeric G protein alpha q subunits through their C2 domain and long C-terminal extension. It regulates neuronal activity in the cerebral cortex and hippocampus, and has been implicated for participations in diverse critical functions related to forebrain diseases such as schizophrenia. It may play an important role in maintenance of the status epilepticus, and in osteosarcoma-related signal transduction pathways. PI-PLC-beta1 also functions as a regulator of erythropoiesis in kinamycin F, a potent inducer of gamma-globin production in K562 cells. The G protein activation and the degradation of PI-PLC-beta1 can be regulated by the interaction of alpha-synuclein. As a result, it may reduce cell damage under oxidative stress. Moreover, PI-PLC-beta1 works as a new intermediate in the HIV-1 gp120-triggered phosphatidylcholine-specific phospholipase C (PC-PLC)-driven signal transduction pathway leading to cytoplasmic CCL2 secretion in macrophages. PI-PLC-beta1 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.