Potency and mechanism of action of E4021, a type 5 phosphodiesterase isozyme-selective inhibitor, on the photoreceptor phosphodiesterase depend on the state of activation of the enzyme

Marc R D'Amours; Alexey E Granovsky; Nikolai O Artemyev; Rick H Cote

doi:10.1016/S0026-895X(24)12175-X

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Potency and mechanism of action of E4021, a type 5 phosphodiesterase isozyme-selective inhibitor, on the photoreceptor phosphodiesterase depend on the state of activation of the enzyme

Journal article

Peer reviewed

Potency and mechanism of action of E4021, a type 5 phosphodiesterase isozyme-selective inhibitor, on the photoreceptor phosphodiesterase depend on the state of activation of the enzyme

Marc R D'Amours, Alexey E Granovsky, Nikolai O Artemyev and Rick H Cote

Molecular pharmacology, Vol.55(3), pp.508-514

03/1999

DOI: 10.1016/S0026-895X(24)12175-X

PMID: 10051534

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Abstract

The ability of inhibitors selective for the type 5 phosphodiesterase isozyme (PDE5) to act on the photoreceptor PDE isozyme (PDE6, the central effector enzyme for visual transduction) is poorly understood. Because PDE5 inhibitors are currently used as therapeutic agents, it is important to assess the potency and mechanism of action of this class of PDE inhibitor on PDE6. We show that E4021 (sodium 1-[6-chloro-4-(3, 4-methylenedioxybenzyl)-aminoquinazolin-2-yl]piperidine-4-ca rboxylate sesquihydrate) inhibits activated PDE6 (KI = 1.7 nM) as potently as PDE5. This makes E4021 the most potent inhibitor of PDE6 discovered to date. The effectiveness of E4021 to inhibit nonactivated PDE6 (with bound inhibitory gamma subunits) is reduced 40-fold compared with the activated enzyme. Furthermore, at intermediate E4021 concentrations and high cGMP concentrations, nonactivated PDE undergoes activation of cGMP hydrolysis rather than inhibition. We demonstrate direct competition of E4021 and the gamma subunits for binding to the catalytic site. Measurements of cGMP binding to noncatalytic regulatory sites on the catalytic subunits of PDE6 rule out an allosteric effect of E4021 by direct binding to these noncatalytic sites. We conclude that E4021 is a competitive inhibitor of cGMP hydrolysis and that the gamma subunit also competes with both E4021 and substrate for catalytic site binding. An understanding of the effects of PDE5-targeted drugs on retinal PDE6 requires a knowledge of the complex interactions among substrate, drug, and inhibitory gamma subunit at the catalytic site of both nonactivated and activated forms of PDE6.

Binding, Competitive

Catalytic Domain

Cyclic Nucleotide Phosphodiesterases, Type 5

Photoreceptor Cells, Vertebrate - drug effects

Phosphodiesterase Inhibitors - pharmacology

3',5'-Cyclic-GMP Phosphodiesterases - metabolism

Animals

Holoenzymes - metabolism

Cyclic GMP - metabolism

Piperidines - pharmacology

3',5'-Cyclic-GMP Phosphodiesterases - antagonists & inhibitors

Cyclic Nucleotide Phosphodiesterases, Type 6

Ranidae

Enzyme Activation

Photoreceptor Cells, Vertebrate - metabolism

Quinazolines - pharmacology

Isoenzymes - antagonists & inhibitors

Details

Title: Subtitle: Potency and mechanism of action of E4021, a type 5 phosphodiesterase isozyme-selective inhibitor, on the photoreceptor phosphodiesterase depend on the state of activation of the enzyme
Creators: Marc R D'Amours - Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham 03824-3544, USA
Alexey E Granovsky
Nikolai O Artemyev
Rick H Cote
Resource Type: Journal article
Publication Details: Molecular pharmacology, Vol.55(3), pp.508-514
Publisher: United States
DOI: 10.1016/S0026-895X(24)12175-X
PMID: 10051534
ISSN: 0026-895X
eISSN: 1521-0111
Grant note: R01 EY005798 / NEI NIH HHS EY-05798 / NEI NIH HHS EY-10843 / NEI NIH HHS
Language: English
Date published: 03/1999
Academic Unit: Molecular Physiology and Biophysics; Iowa Neuroscience Institute; Ophthalmology and Visual Sciences
Record Identifier: 9984071638602771

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