IRAG mediates NO/cGMP-dependent inhibition of platelet aggregation and thrombus formation

Blood. 2007 Jan 15;109(2):552-9. doi: 10.1182/blood-2005-10-026294. Epub 2006 Sep 21.

Abstract

Defective regulation of platelet activation/aggregation is a predominant cause for arterial thrombosis, the major complication of atherosclerosis triggering myocardial infarction and stroke. A central regulatory pathway conveying inhibition of platelet activation/aggregation is nitric oxide (NO)/cyclic GMP (cGMP) signaling by cGMP-dependent protein kinase I (cGKI). However, the regulatory cascade downstream of cGKI mediating platelet inhibition is still unclear. Here, we show that the inositol-1,4,5-trisphosphate receptor-associated cGMP kinase substrate (IRAG) is abundantly expressed in platelets and assembled in a macrocomplex together with cGKIbeta and the inositol-1,4,5-trisphosphate receptor type I (InsP3RI). cGKI phosphorylates IRAG at Ser664 and Ser677 in intact platelets. Targeted deletion of the IRAG-InsP3RI interaction in IRAGDelta12/Delta12 mutant mice leads to a loss of NO/cGMP-dependent inhibition of fibrinogen-receptor activation and platelet aggregation. Intracellular calcium transients were not affected by DEA/NO or cGMP in mutant platelets. Furthermore, intravital microscopy shows that NO fails to prevent arterial thrombosis of the injured carotid artery in IRAGDelta12/Delta12 mutants. These findings reveal that interaction between IRAG and InsP3RI has a central role in NO/cGMP-dependent inhibition of platelet aggregation and in vivo thrombosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism
  • Cyclic GMP / metabolism*
  • Cyclic GMP-Dependent Protein Kinases / metabolism
  • Enzyme Activators / pharmacology
  • Humans
  • Inositol 1,4,5-Trisphosphate Receptors / metabolism
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Membrane Proteins / genetics
  • Membrane Proteins / physiology*
  • Mice
  • Mice, Knockout
  • Multiprotein Complexes / metabolism
  • Nitric Oxide / metabolism*
  • Phosphoproteins / genetics
  • Phosphoproteins / physiology*
  • Phosphorylation
  • Platelet Aggregation / drug effects
  • Platelet Aggregation / physiology*
  • Reference Values
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • Thrombosis / metabolism
  • Thrombosis / prevention & control*

Substances

  • Enzyme Activators
  • IRAG1 protein, human
  • Inositol 1,4,5-Trisphosphate Receptors
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Multiprotein Complexes
  • Phosphoproteins
  • protein kinase modulator
  • Nitric Oxide
  • Cyclic GMP-Dependent Protein Kinases
  • Cyclic GMP
  • Calcium