title: Apart from its known function, the plasma membrane Ca²⁺ATPase can regulate Ca²⁺ signaling by controlling phosphatidylinositol 4,5-bisphosphate levels.
abstract: Plasma membrane Ca(2+) ATPases (PMCAs, also known as ATP2B1-ATP2B4) are known targets of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P₂], but if and how they control the PtdIns(4,5)P₂ pool has not been considered. We demonstrate here that PMCAs protect PtdIns(4,5)P₂ in the plasma membrane from hydrolysis by phospholipase C (PLC). Comparison of active and inactive PMCAs indicates that the protection operates by two mechanisms; one requiring active PMCAs, the other not. It appears that the mechanism requiring activity is the removal of the Ca(2+) required for sustained PLC activity, whereas the mechanism not requiring activity is PtdIns(4,5)P₂ binding. We show that in PMCA overexpressing cells, PtdIns(4,5)P₂ binding can lead to less inositol 1,4,5-triphosphate (InsP₃) and diminished Ca(2+) release from intracellular Ca(2+) pools. Inspection of a homology model of PMCA suggests that PMCAs have a conserved cluster of basic residues forming a 'blue collar' at the interface between the membrane core and the cytoplasmic domains. By molecular dynamics simulation, we found that the blue collar forms four binding pockets for the phosphorylated inositol head group of PtdIns(4,5)P₂; these pockets bind PtdIns(4,5)P₂ strongly and frequently. Our studies suggest that by having the ability to bind PtdIns(4,5)P₂, PMCAs can control the accessibility of PtdIns(4,5)P₂ for PLC and other PtdIns(4,5)P₂-mediated processes.
authors.affiliation: Institute of Molecular Pharmacology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, H-1025 Budapest, Hungary.
authors.forename: John T
authors.initials: JT
authors.lastname: Penniston
authors.forename: Rita
authors.initials: R
authors.lastname: Padányi
authors.forename: Katalin
authors.initials: K
authors.lastname: Pászty
authors.forename: Karolina
authors.initials: K
authors.lastname: Varga
authors.forename: Luca
authors.initials: L
authors.lastname: Hegedus
authors.forename: Agnes
authors.initials: A
authors.lastname: Enyedi
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D000252:Calcium-Transporting ATPases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D015870:Gene Expression; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D015544:Inositol 1,4,5-Trisphosphate / Q000737:chemistry / Q000378:metabolism*; D017136:Ion Transport; D056004:Molecular Dynamics Simulation; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011817:Rabbits; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D019269:Phosphatidylinositol 4,5-Diphosphate; D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D000252:Calcium-Transporting ATPases; D002118:Calcium
keywords: Ca2+ signaling; Molecular dynamics simulation; PMCA; Phosphatidylinositol 4,5,-bisphosphate; Plasma membrane Ca2+ ATPase; PtdIns(4,5)P2