title: IRAG mediates NO/cGMP-dependent inhibition of platelet aggregation and thrombus formation.
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.
authors.affiliation: Institut für Pharmakologie und Toxikologie der Technischen Universität München, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Antl
authors.forename: Marie-Luise
authors.initials: ML
authors.lastname: von Brühl
authors.forename: Christina
authors.initials: C
authors.lastname: Eiglsperger
authors.forename: Matthias
authors.initials: M
authors.lastname: Werner
authors.forename: Ildiko
authors.initials: I
authors.lastname: Konrad
authors.forename: Thomas
authors.initials: T
authors.lastname: Kocher
authors.forename: Matthias
authors.initials: M
authors.lastname: Wilm
authors.forename: Franz
authors.initials: F
authors.lastname: Hofmann
authors.forename: Steffen
authors.initials: S
authors.lastname: Massberg
authors.forename: Jens
authors.initials: J
authors.lastname: Schlossmann
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D020536:Enzyme Activators / Q000494:pharmacology; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D046912:Multiprotein Complexes / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology*; D012016:Reference Values; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013927:Thrombosis / Q000378:metabolism / Q000517:prevention & control*
chemical_list: D020536:Enzyme Activators; C485784:IRAG1 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D010750:Phosphoproteins; C015482:protein kinase modulator; D009569:Nitric Oxide; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP; D002118:Calcium