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J. Biol. Chem., Vol. 282, Issue 45, 32749-32757, November 9, 2007

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Cyclic Nucleotide Phosphodiesterase PDE1C1 in Human Cardiac Myocytes^*

Fabrice Vandeput¹, Sharon L. Wolda^¶1, Judith Krall, Ryan Hambleton, Lothar Uher^¶, Kim N. McCaw^¶, Przemyslaw B. Radwanski, Vincent Florio^¶, and Matthew A. Movsesian²

From the Cardiology Section, Veterans Affairs Salt Lake City Health Care System, Salt Lake City, Utah 84148, and the Departments of Internal Medicine (Cardiology) and Pharmacology, University of Utah School of Medicine, Salt Lake City, Utah 84132, and ^¶ICOS Corporation, Bothell, Washington 98021

Isoforms in the PDE1 family of cyclic nucleotide phosphodiesterases were recently found to comprise a significant portion of the cGMP-inhibited cAMP hydrolytic activity in human hearts. We examined the expression of PDE1 isoforms in human myocardium, characterized their catalytic activity, and quantified their contribution to cAMP hydrolytic and cGMP hydrolytic activity in subcellular fractions of this tissue. Western blotting with isoform-selective anti-PDE1 monoclonal antibodies showed PDE1C1 to be the principal isoform expressed in human myocardium. Immunohistochemical analysis showed that PDE1C1 is distributed along the Z-lines and M-lines of cardiac myocytes in a striated pattern that differs from that of the other major dual-specificity cyclic nucleotide phosphodiesterase in human myocardium, PDE3A. Most of the PDE1C1 activity was recovered in soluble fractions of human myocardium. It binds both cAMP and cGMP with K_m values of 1 µM and hydrolyzes both substrates with similar catalytic rates. PDE1C1 activity in subcellular fractions was quantified using a new PDE1-selective inhibitor, IC295. At substrate concentrations of 0.1 µM, PDE1C1 constitutes the great majority of cAMP hydrolytic and cGMP hydrolytic activity in soluble fractions and the majority of cGMP hydrolytic activity in microsomal fractions, whereas PDE3 constitutes the majority of cAMP hydrolytic activity in microsomal fractions. These results indicate that PDE1C1 is expressed at high levels in human cardiac myocytes with an intracellular distribution distinct from that of PDE3A and that it may have a role in the integration of cGMP-, cAMP- and Ca²⁺-mediated signaling in these cells.

Received for publication, April 16, 2007 , and in revised form, August 21, 2007.

^* This work was supported by Medical Research funds from the United States Department of Veterans Affairs and grants from the Fondation Leducq for the Transatlantic Network of Excellence 06 CVD 02 and the American Heart Association (to M. A. M.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ Both authors contributed equally to this work.

² To whom correspondence should be addressed: Cardiology Section, Veterans Affairs Salt Lake City Health Care System, 500 Foothill Blvd., Salt Lake City, UT 84148. Tel.: 801-582-1565 (Ext. 4156); Fax: 801-584-2532; E-mail: matthew.movsesian{at}hsc.utah.edu.

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