title: Allosteric sites of phosphodiesterase-5 sequester cyclic GMP.
abstract: Phosphodiesterase-5 (PDE5) and cGMP-dependent protein kinase (PKG) play key roles in cGMP signaling. PDE5 has a catalytic domain (C domain) that hydrolyzes cGMP and a regulatory domain (R domain) that binds cGMP at allosteric sites. We recently demonstrated that in corpus cavernosum, PDE5 concentration exceeds basal cGMP by ~5-fold making it possible that its allosteric sites could bind a significant fraction of the total cellular cGMP. It is hypothesized that the allosteric sites regulate cGMP signaling by sequestering cGMP. At 60 nM cGMP in vitro, which approaches a stimulated concentration of cGMP in rabbit corpus cavernosum, isolated R domain inhibits both cGMP hydrolysis by C domain and activation of PKG (IC50 values of 388 and 100 nM, respectively). Prior phosphorylation of R domain by cyclic nucleotide-dependent protein kinases, which increases its cGMP-binding affinity, also increases its potency for inhibiting both cGMP hydrolysis by C domain and cGMP activation of PKG (IC50 values of 58 and 38 nM, respectively). In rabbit corpus cavernosum, PDE5 concentration (94 nM) exceeds these values. These findings support our hypothesis that physiological concentrations of R domain regulate cGMP signaling by sequestering this nucleotide and that phosphorylation of R domain modulates this effect. This could provide for negative feedback control of cGMP-signaling.
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0615, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Kotera
authors.forename: Sharron H
authors.initials: SH
authors.lastname: Francis
authors.forename: Kennard A
authors.initials: KA
authors.lastname: Grimes
authors.forename: Alfreda
authors.initials: A
authors.lastname: Rouse
authors.forename: Mitsi A
authors.initials: MA
authors.lastname: Blount
authors.forename: Jackie D
authors.initials: JD
authors.lastname: Corbin
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases; D000495:Allosteric Site; D000818:Animals; D020134:Catalytic Domain; D002417:Cattle; D006152:Cyclic GMP / Q000378:metabolism*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism*; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D020035:Holoenzymes / Q000378:metabolism; D006868:Hydrolysis; D007313:Insecta / Q000166:cytology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary / Q000502:physiology; D011817:Rabbits
chemical_list: D020035:Holoenzymes; D017869:Cyclic GMP-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D010727:Phosphoric Diester Hydrolases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D006152:Cyclic GMP