title: In vivo reconstitution of the negative feedback in nitric oxide/cGMP signaling: role of phosphodiesterase type 5 phosphorylation.
abstract: Most effects of the messenger molecule nitric oxide (NO) are mediated by cGMP, which is formed by NO-sensitive guanylyl cyclase (GC) and degraded by phosphodiesterases (PDEs). In platelets, NO elicits a spike-like cGMP response and causes a sustained desensitization. Both characteristics have been attributed to PDE5 activation caused by cGMP binding to its regulatory GAF domain. Activation is paralleled by phosphorylation whose precise function remains unknown. Here, we report reconstitution of all features of the NO-induced cGMP response in human embryonic kidney cells by coexpressing NO-sensitive GC and PDE5. The spike-like cGMP response was blunted when PDE5 phosphorylation was enhanced by additional overexpression of cGMP-dependent protein kinase. Analysis of PDE5 activation in vitro revealed a discrepancy between the cGMP concentrations required for activation (micromolar) and reversal of activation (nanomolar), indicating the conversion of a low-affinity state to a high-affinity state upon binding of cGMP. Phosphorylation even increased the high apparent affinity enabling PDE5 activation to persist at extremely low cGMP concentrations. Our data suggest that the spike-like shape and the desensitization of the cGMP response are potentially inherent to every GC- and PDE5-expressing cell. Phosphorylation of PDE5 seems to act as memory switch for activation leading to long-term desensitization of the signaling pathway.
authors.affiliation: Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Ruhr-Universität Bochum, Bochum, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Mullershausen
authors.forename: Michael
authors.initials: M
authors.lastname: Russwurm
authors.forename: Doris
authors.initials: D
authors.lastname: Koesling
authors.forename: Andreas
authors.initials: A
authors.lastname: Friebe
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006152:Cyclic GMP / Q000378:metabolism*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D004789:Enzyme Activation; D005246:Feedback; D015870:Gene Expression; D006162:Guanylate Cyclase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D009569:Nitric Oxide / Q000378:metabolism* / Q000494:pharmacology; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D026422:S-Nitrosoglutathione / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection
chemical_list: D011994:Recombinant Proteins; D009569:Nitric Oxide; D026422:S-Nitrosoglutathione; D017869:Cyclic GMP-Dependent Protein Kinases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; C517381:PDE5A protein, human; D006162:Guanylate Cyclase; D006152:Cyclic GMP