title: Lyn, PKC-delta, SHIP-1 interactions regulate GPVI-mediated platelet-dense granule secretion.
abstract: Protein kinase C-delta (PKC-delta) is expressed in platelets and activated downstream of protease-activated receptors (PARs) and glycoprotein VI (GPVI) receptors. We have previously shown that PKC-delta positively regulates PAR-mediated dense granule secretion, whereas it negatively regulates GPVI-mediated dense granule secretion. We further investigated the mechanism of such differential regulation of dense granule release by PKC-delta in platelets. SH2 domain-containing inositol phosphatase-1 (SHIP-1) is phosphorylated on Y1020, a marker for its activation, upon stimulation of human platelets with PAR agonists SFLLRN and AYPGKF or GPVI agonist convulxin. GPVI-mediated SHIP-1 phosphorylation occurred rapidly at 15 seconds, whereas PAR-mediated phosphorylation was delayed, occurring at 1 minute. Lyn and SHIP-1, but not SHIP-2 or Shc, preferentially associated with PKC-delta on stimulation of platelets with a GPVI agonist, but not with a PAR agonist. In PKC-delta-null murine platelets, convulxin-induced SHIP-1 phosphorylation was inhibited. Furthermore, in Lyn null murine platelets, GPVI-mediated phosphorylations on Y-1020 of SHIP-1 and Y311 of PKC-delta were inhibited. In murine platelets lacking Lyn or SHIP-1, GPVI-mediated dense granule secretions are potentiated, whereas PAR-mediated dense granule secretions are inhibited. Therefore, we conclude that Lyn-mediated phosphorylations of PKC-delta and SHIP-1 and their associations negatively regulate GPVI-mediated dense granule secretion in platelets.
authors: Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
authors: Ramya
authors: R
authors: Chari
authors: Soochong
authors: S
authors: Kim
authors: Swaminathan
authors: S
authors: Murugappan
authors: Archana
authors: A
authors: Sanjay
authors: James L
authors: JL
authors: Daniel
authors: Satya P
authors: SP
authors: Kunapuli
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D015153:Blotting, Western; D005260:Female; D047468:Immunoprecipitation; D000072181:Inositol Polyphosphate 5-Phosphatases; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000502:physiology*; D010766:Phosphorylation; D010980:Platelet Membrane Glycoproteins / Q000502:physiology*; D051745:Protein Kinase C-delta / Q000502:physiology*; D051076:Proto-Oncogene Proteins c-fyn / Q000502:physiology; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000502:physiology; D022142:Secretory Vesicles / Q000378:metabolism*; D015398:Signal Transduction; D019061:src-Family Kinases / Q000502:physiology*
chemical_list: D010980:Platelet Membrane Glycoproteins; C098341:platelet membrane glycoprotein VI; C494960:Fyn protein, mouse; D051076:Proto-Oncogene Proteins c-fyn; D016392:Proto-Oncogene Proteins pp60(c-src); C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D051745:Protein Kinase C-delta; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; C000606430:INPP5D protein, human; C000606433:Inpp5d protein, mouse; C000606435:Inppl1 protein, mouse; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases