Differential role of protein kinase C delta isoform in agonist-induced dense granule secretion in human platelets

J Biol Chem. 2004 Jan 23;279(4):2360-7. doi: 10.1074/jbc.M306960200. Epub 2003 Oct 24.

Abstract

Several platelet agonists, including thrombin, collagen, and thromboxane A(2), cause dense granule release independently of thromboxane generation. Because protein kinase C (PKC) isoforms are implicated in platelet secretion, we investigated the role of individual PKC isoforms in platelet dense granule release. PKCdelta was phosphorylated in a time-dependent manner that coincided with dense granule release in response to protease-activated receptor-activating peptides SFLLRN and AYPGKF in human platelets. Only agonists that caused platelet dense granule secretion activated PKCdelta. SFLLRN- or AYPGKF-induced dense granule release and PKCdelta phosphorylation occurred at the same respective agonist concentration. Furthermore, AYPGKF and SFLLRN-induced dense granule release was blocked by rottlerin, a PKCdelta selective inhibitor. In contrast, convulxin-induced dense granule secretion was potentiated by rottlerin but was abolished by Go6976, a classical PKC isoform inhibitor. However, SFLLRN-induced dense granule release was unaffected in the presence of Go6976. Finally, rottlerin did not affect SFLLRN-induced platelet aggregation, even in the presence of dimethyl-BAPTA, indicating that PKCdelta has no role in platelet fibrinogen receptor activation. We conclude that PKCdelta and the classical PKC isoforms play a differential role in platelet dense granule release mediated by protease-activated receptors and glycoprotein VI. Furthermore, PKCdelta plays a positive role in protease-activated receptor-mediated dense granule secretion, whereas it functions as a negative regulator downstream of glycoprotein VI signaling.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Blood Platelets / physiology*
  • Cell Degranulation / drug effects
  • Cell Degranulation / physiology*
  • Humans
  • Isoenzymes / drug effects
  • Isoenzymes / physiology
  • Oligopeptides / pharmacology
  • Peptide Fragments / pharmacology
  • Phosphorylation / drug effects
  • Platelet Membrane Glycoproteins / physiology
  • Protein Kinase C / drug effects
  • Protein Kinase C / physiology*
  • Protein Kinase C-delta
  • Secretory Vesicles / drug effects
  • Secretory Vesicles / physiology
  • Signal Transduction / drug effects

Substances

  • Isoenzymes
  • Oligopeptides
  • Peptide Fragments
  • Platelet Membrane Glycoproteins
  • alanyl-tyrosyl-prolyl-glycyl-lysyl-phenylalanine
  • thrombin receptor peptide (42-47)
  • PRKCD protein, human
  • Protein Kinase C
  • Protein Kinase C-delta