title: Activation of a phosphatidylcholine-specific phospholipase C by colony stimulating factor 1 receptor requires tyrosine phosphorylation and a guanine nucleotide-binding protein.
abstract: Receptor tyrosine kinases couple to multiple intracellular effector molecules that are crucial for normal cell growth and transformation. Stimulation of membrane phospholipid hydrolysis by receptor tyrosine kinases is one such pathway for generating intracellular second messengers that may be important for mitogenesis. Certain receptor tyrosine kinases tyrosine phosphorylate a phosphoinositide-specific phospholipase C that hydrolyses the membrane phospholipid phosphatidylinositol 4,5-bisphosphate. In contrast, the glycoprotein receptor for colony stimulating factor 1, a transmembrane tyrosine kinase, does not utilize this pathway, but rather stimulates the hydrolysis of phosphatidylcholine. Here we show that eluates of antiphosphotyrosine affinity purified lysates of colony-stimulating factor 1-stimulated cells contain elevated levels of phosphatidylcholine-specific phospholipase C activity. The affinity-purified activity is sensitive to tyrosine-specific T-cell phosphatase, and is detected in the membrane fraction of stimulated cells. Recovery of phospholipase C activity in the antiphosphotyrosine protein fraction is reduced by pertussis toxin pretreatment of cells. The phosphatidylcholine phospholipase C activity in isolated membranes of colony-stimulating factor 1-treated cells was also reduced by pertussis toxin treatment and stimulated by guanosine 5'-3-O-(thio)triphosphate. These results indicate that colony stimulating factor 1 receptor-mediated stimulation of phosphatidylcholine-specific phospholipase C requires tyrosine phosphorylation, and might be affected by a G-protein coupled pathway.
authors.affiliation: Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284-7762.
authors.forename: G G
authors.initials: GG
authors.lastname: Choudhury
authors.forename: V L
authors.initials: VL
authors.lastname: Sylvia
authors.forename: A Y
authors.initials: AY
authors.lastname: Sakaguchi
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D037342:Pertussis Toxin; D010713:Phosphatidylcholines / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D011916:Rats, Inbred F344; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000378:metabolism*; D013379:Substrate Specificity; D010738:Type C Phospholipases / Q000187:drug effects / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D010713:Phosphatidylcholines; D010566:Virulence Factors, Bordetella; D014443:Tyrosine; D016173:Macrophage Colony-Stimulating Factor; D037342:Pertussis Toxin; D016186:Receptor, Macrophage Colony-Stimulating Factor; D010744:Phosphoric Monoester Hydrolases; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins