cGMP-dependent protein kinase protects cGMP from hydrolysis by phosphodiesterase-5.
The physiological effects of cGMP are largely determined by the activities of intracellular receptors, including cGMP-dependent protein kinase (PKG) and cGMP-binding cyclic nucleotide phosphodiesterases (PDEs), and the distribution of cGMP among these receptors dictates activity of the signalling pathway. In the present study, the effects of PKG-Ialpha or PKG-Ibeta on the rate of cGMP hydrolysis by the isolated PDE5 catalytic domain were examined. PKG-Ialpha strongly inhibited cGMP hydrolysis with an IC(50) value of 217 nM, which is similar to the physiological concentration of PKG in pig coronary artery reported previously. By contrast, PKG-Ibeta, which has lower affinity for cGMP than does PKG-Ialpha, inhibited cGMP hydrolysis with an IC(50) of approx. 1 microM. Inhibition by PKG-Ialpha was more effective than that by PKG-Ibeta, consistent with their relative affinities for cGMP. Autophosphorylation of PKGs increased their cGMP-binding affinities and their inhibitory effects on PDE5 hydrolysis of cGMP. Autophosphorylation of PKG-Ibeta increased its inhibitory potency on PDE5 hydrolysis of cGMP by 10-fold compared with a 2-fold increase upon autophosphorylation of PKG-Ialpha. The results indicate that cGMP bound to allosteric cGMP-binding sites of PKG is protected from hydrolysis by PDE5 and that persistent protection of cGMP by either non-phosphorylated or autophosphorylated PKGs may be a positive-feedback control to sustain cGMP signalling.
Kotera
Jun
J
Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0615, USA.
Grimes
Kennard A
KA
Corbin
Jackie D
JD
Francis
Sharron H
SH
D015106:3',5'-Cyclic-GMP Phosphodiesterases; D000494:Allosteric Regulation; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D006152:Cyclic GMP / Q000378:metabolism*; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases / Q000494:pharmacology*; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D018076:DNA, Complementary / Q000378:metabolism; D019281:Dimerization; D004789:Enzyme Activation; D006868:Hydrolysis; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D010727:Phosphoric Diester Hydrolases / Q000494:pharmacology*; D010766:Phosphorylation; D011485:Protein Binding; D011994:Recombinant Proteins
D018076:DNA, Complementary; D011994:Recombinant Proteins; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases; D010727:Phosphoric Diester Hydrolases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D006152:Cyclic GMP