The NO/cGMP pathway inhibits Rap1 activation in human platelets via cGMP-dependent protein kinase I

  • The NO/cGMP signalling pathway strongly inhibits agonist-induced platelet aggregation. However, the molecular mechanisms involved are not completely defined.We have studied NO/cGMP effects on the activity of Rap1, an abundant guanine-nucleotidebinding protein in platelets. Rap1-GTP levels were reduced by NO-donors and activators of NO-sensitive soluble guanylyl cyclase. Four lines of evidence suggest that NO/cGMP effects are mediated by cGMP-dependent protein kinase (cGKI): (i) Rap1 inhibition correlated with cGKI activity as measured by the phosphorylation state ofVASP, an established substrate of cGKI, (ii) 8-pCPT-cGMP, a membrane permeable cGMP-analog and activator of cGKI, completely blocked Rap1 activation, (iii) Rp- 8pCPT-cGMPS, a cGKI inhibitor, reversed NO effects and (iv) expression of cGKI in cGKI-deficient megakaryocytes inhibited Rap1 activation. NO/cGMP/cGKI effects were independent of the type of stimulus used for Rap1 activation.Thrombin-,ADPand collagen-induced formation of Rap1-GTP in platelets as well as turbulence-induced Rap1 activation in megakaryocytes were inhibited. Furthermore, cGKI inhibited ADP-induced Rap1 activation induced by the G a i -coupled P2Y12 receptor alone, i.e. independently of effects on Ca2+-signalling. From these studies we conclude that NO/cGMP inhibit Rap1 activation in human platelets and that this effect is mediated by cGKI. Since Rap1 controls the function of integrin a IIbß 3 , we propose that Rap1 inhibition might play a central role in the anti-aggregatory actions of NO/cGMP.

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Author:Oliver Danielewski, Jan Schultess, Albert SmolenskiGND
Parent Title (English):Thrombosis and haemostasis
Place of publication:Stuttgart
Document Type:Article
Date of Publication (online):2014/11/25
Year of first Publication:2005
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2014/11/25
Tag:Kinase; Nitric oxide; Platelet physiology; Rap1; cGMP
Page Number:26
First Page:319
Last Page:325
This article is not an exact copy of the original published article in Thrombosis and Haemostasis. The definitive publisher-authenticated version of Danielewski O., Schultess J. and Smolenski A. 'The NO/cGMP pathway inhibits Rap 1 activation in human platelets via cGMP-dependent protein kinase I', 93(2): 319-325 is available online at
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Institutes:Biochemie, Chemie und Pharmazie / Biochemie und Chemie
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 57 Biowissenschaften; Biologie / 570 Biowissenschaften; Biologie
Sammlung Biologie / Sondersammelgebiets-Volltexte
Licence (German):License LogoCreative Commons - Namensnennung-Nicht kommerziell-Keine Bearbeitung 3.0