title: Direct activation of PDE5 by cGMP: long-term effects within NO/cGMP signaling.
abstract: In platelets, the nitric oxide (NO)-induced cGMP response is indicative of a highly regulated interplay of cGMP formation and cGMP degradation. Recently, we showed that within the NO-induced cGMP response in human platelets, activation and phosphorylation of phosphodiesterase type 5 (PDE5) occurred. Here, we identify cyclic GMP-dependent protein kinase I as the kinase responsible for the NO-induced PDE5 phosphorylation. However, we demonstrate that cGMP can directly activate PDE5 without phosphorylation in platelet cytosol, most likely via binding to the regulatory GAF domains. The reversal of activation was slow, and was not completed after 60 min. Phosphorylation enhanced the cGMP-induced activation, allowing it to occur at lower cGMP concentrations. Also, in intact platelets, a sustained NO-induced activation of PDE5 for as long as 60 min was detected. Finally, the long-term desensitization of the cGMP response induced by a low NO concentration reveals the physiological relevance of the PDE5 activation within NO/cGMP signaling. In sum, we suggest NO-induced activation and phosphorylation of PDE5 as the mechanism for a long-lasting negative feedback loop shaping the cGMP response in human platelets in order to adapt to the amount of NO available.
authors.affiliation: Abteilung für Pharmakologie und Toxikologie, Medizinische Fakultät, Ruhr-Universität Bochum, MA N1/43, Universitaetsstr. 150, 44780 Bochum, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Mullershausen
authors.forename: Andreas
authors.initials: A
authors.lastname: Friebe
authors.forename: Robert
authors.initials: R
authors.lastname: Feil
authors.forename: W Joseph
authors.initials: WJ
authors.lastname: Thompson
authors.forename: Franz
authors.initials: F
authors.lastname: Hofmann
authors.forename: Doris
authors.initials: D
authors.lastname: Koesling
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases; D000818:Animals; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism* / Q000494:pharmacology; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases / Q000172:deficiency / Q000235:genetics; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D004791:Enzyme Inhibitors / Q000494:pharmacology; D025461:Feedback, Physiological / Q000187:drug effects / Q000502:physiology*; D005260:Female; D016166:Free Radical Scavengers / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008840:Microfilament Proteins; D009569:Nitric Oxide / Q000378:metabolism* / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D015815:Cell Adhesion Molecules; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D008840:Microfilament Proteins; D020030:Nitric Oxide Donors; D010750:Phosphoproteins; D000098662:Vasodilator-Stimulated Phosphoprotein; D009569:Nitric Oxide; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases; C569718:PRKG1 protein, human; C569720:Prkg1 protein, mouse; D010727:Phosphoric Diester Hydrolases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; C517381:PDE5A protein, human; C517382:Pde5a protein, mouse; D006162:Guanylate Cyclase; D006152:Cyclic GMP