title: Phospholipase C-gamma 1 is translocated to the membrane of rat basophilic leukemia cells in response to aggregation of IgE receptors.
abstract: Aggregation of the high affinity receptor for IgE (Fc epsilon RI) on the surface of mast cells results in the rapid hydrolysis of membrane inositol phospholipids by phospholipase C (PLC). Although at least seven isoenzymes of PLC have been characterized in different mammalian cells, the isoenzyme involved in Fc epsilon RI-mediated signal transduction and the mechanism of its activation have not been demonstrated. We now report that PLC-gamma 1 is translocated to the membrane of mast cells after aggregation of Fc epsilon RI. Activation of rat basophilic leukemia cells, a rat mast cell line, with oligomeric IgE resulted in an increase in PLC activity in washed membrane preparations in a cell free assay containing exogenous [3H]phosphatidylinositol (PI). The increase in PLC activity has the same dose-response to oligomeric IgE as receptor mediated hydrolysis of inositol lipids (PI hydrolysis) in intact cells. Analysis by Western blot probed with anti-PLC-gamma 1 antibody revealed that there is a three- to fourfold increase in PLC-gamma 1 in membranes from activated cells. The increase in PLC activity is augmented a further 20% by the addition of orthovanadate to the incubation medium suggesting that a tyrosine phosphatase is involved in the down-regulation of this phenomenon. These findings demonstrate translocation of PLC-gamma 1 to the membrane following activation of a receptor which does not contain intrinsic tyrosine kinase activity. Activation of PLC-gamma 1 by this pathway may account for Fc epsilon RI-mediated PI hydrolysis.
authors.affiliation: National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
authors.forename: T P
authors.initials: TP
authors.lastname: Atkinson
authors.forename: M A
authors.initials: MA
authors.lastname: Kaliner
authors.forename: R J
authors.initials: RJ
authors.lastname: Hohman
mesh_terms: D000818:Animals; D000944:Antigens, Differentiation, B-Lymphocyte / Q000502:physiology*; D001692:Biological Transport; D002462:Cell Membrane / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D007073:Immunoglobulin E / Q000378:metabolism*; D015471:Leukemia, Basophilic, Acute / Q000201:enzymology*; D051379:Mice; D010716:Phosphatidylinositols / Q000378:metabolism; D010766:Phosphorylation; D011817:Rabbits; D051381:Rats; D011961:Receptors, Fc / Q000502:physiology*; D017455:Receptors, IgE; D013696:Temperature; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D010716:Phosphatidylinositols; D011961:Receptors, Fc; D017455:Receptors, IgE; D007073:Immunoglobulin E; D014443:Tyrosine; D010738:Type C Phospholipases