title: Ca2+ regulation of phosphatidylinositol turnover in the plasma membrane of tobacco suspension culture cells.
abstract: The biochemical properties of the enzymes involved in phosphatidylinositol (PI) turnover in higher plants were investigated using the plasma membrane isolated from tobacco suspension culture cells by aqueous two-phase partitioning. Submicromolar concentrations of Ca2+ inhibited PI kinase and phosphatidylinositol 4-phosphate (PIP) kinase and stimulated phospholipase C. Diacylglycerol (DG) kinase was inhibited by Ca2+, but required a higher concentration than the physiological level. From the above results we postulate the following scheme: signal coupled activation of phospholipase C produces IP3 which induces Ca2+ release from the intracellular Ca2+ compartment, the increased cytoplasmic Ca2+ in turn activates phospholipase C and causes a further increase of the cytoplasmic Ca2+ level. This inhibits PI kinase and PIP kinase and brings about a limited supply of PIP2, the substrate of phospholipase C. Consequently, IP3 production decreases and Ca2+ mobilization ceases. Then cytosolic Ca2+ returns to the stationary level by the Ca2+ pump at the plasma membrane and at the endoplasmic reticulum and Ca2+/H+ antiporter at the plasma membrane and at the tonoplast.
authors.affiliation: Institute of Applied Microbiology, University of Tokyo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kamada
authors.forename: S
authors.initials: S
authors.lastname: Muto
mesh_terms: D019870:1-Phosphatidylinositol 4-Kinase; D000255:Adenosine Triphosphate / Q000378:metabolism; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D019852:Diacylglycerol Kinase; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D017830:Octoxynol; D010716:Phosphatidylinositols / Q000378:metabolism*; D010770:Phosphotransferases / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor); D010944:Plants / Q000201:enzymology / Q000378:metabolism*; D010947:Plants, Toxic; D011092:Polyethylene Glycols / Q000494:pharmacology; D014026:Nicotiana; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D010716:Phosphatidylinositols; D011092:Polyethylene Glycols; D000255:Adenosine Triphosphate; D017830:Octoxynol; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); D019852:Diacylglycerol Kinase; D019870:1-Phosphatidylinositol 4-Kinase; C020077:1-phosphatidylinositol-4-phosphate 5-kinase; D010738:Type C Phospholipases; D008274:Magnesium; D002118:Calcium