title: A predominant role for cAMP-dependent protein kinase in the cGMP-induced phosphorylation of vasodilator-stimulated phosphoprotein and platelet inhibition in humans.
abstract: The vasodilator-stimulated phosphoprotein (VASP) plays an important role in cGMP-induced platelet inhibition. Since VASP is an in vitro substrate for cGMP-dependent protein kinase (PKG), it has been presumed that VASP phosphorylation induced by cGMP is mediated by PKG. Here we show that, in human platelets, phosphorylation of VASP at Ser239 induced by either cGMP analogs or nitric oxide (NO) donor glyco-SNAP1 is inhibited by PKA inhibitors KT5720, PKI, Rp-Br-cAMPS, and H89, but not by PKG inhibitors KT5823 or Rp-pCPT-cGMPS. Unlike human platelets, cGMP analog-induced phosphorylation of VASP in mouse platelets is inhibited by both PKG and PKA inhibitors. Ineffectiveness of PKG inhibitors in inhibiting VASP phosphorylation in human platelets is not due to an inability to inhibit PKG, as these PKG inhibitors but not PKA inhibitors inhibit a different cGMP-induced intracellular signaling event: phosphorylation of extracellular signal-responsive kinase. Furthermore, PKA inhibitors reverse cGMP-induced inhibition of thrombin-induced platelet aggregation, whereas PKG inhibitors further enhance the inhibitory effect of cGMP analogs. Thus, PKA plays a predominant role in the cGMP-induced phosphorylation of VASP and platelet inhibition in human platelets.
authors.affiliation: Department of Pharmacology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Li
authors.forename: Jasna
authors.initials: J
authors.lastname: Ajdic
authors.forename: Martin
authors.initials: M
authors.lastname: Eigenthaler
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Du
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D010974:Platelet Aggregation; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D015815:Cell Adhesion Molecules; D004791:Enzyme Inhibitors; D008840:Microfilament Proteins; D020030:Nitric Oxide Donors; D010750:Phosphoproteins; D000098662:Vasodilator-Stimulated Phosphoprotein; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP