PDE3A is an important regulator of sarcoplasmic reticulum Ca2+-ATPase (SERCA2) activity

Tuesday, October 25, 2011 — Poster Session II
Noon – 2:00 p.m.	Natcher Conference Center	NHLBI	SIG/RNA/CYTOK-8

Authors

• F Khan
• W Shen
• S Beca
• S Hockman
• P Backx
• V Manganiello

Abstract

PDE3 plays an important role in regulating cAMP metabolism in the cardiovascular system. Although PDE3 inhibitors, by raising cAMP, produce acute inotropic and vasodilatory effects, the detailed mechanisms for these actions are unclear. In our experiments, PDE3A cofractionates with Ca2+-ATPase 2 (SERCA2) and phospholamban during sucrose gradient centrifugation of cardiac membranes, and colocalizes with SERCA2 and desmin in WT heart tissue. Using LC-MS/MS analysis of PDE3A immunoprecipitates, we found that PDE3A coimmunoprecipitated with SERCA2. Immunoblot and enzyme activity assays indicated that PDE3A coimmunoprecipitated with SERCA2, PLN, PP2A and AKAP18. In cardiac microsomes from WT and PDE3A-/- mice, SERCA2 activity and Ca2+ uptake were increased in KO fractions, compared to WT, and phosphorylation of phospholamban at Ser16 was increased. Cilostamide, specific PDE3 inhibitor, increased Ca2+ uptake into WT SR fractions. SR fractions from PDE3A-/- hearts showed a 2-fold reduction in total PDE activity, compared to WT, and reductions in PDE3 activity without changes in PDE4 activity, which is associated with increased phosphorylation of PKA-related protein targets. These data suggest that, as component of a SERCA2-containing macromolecular complex, PDE3A regulates a discrete cAMP pool important in mediating some effects of SERCA2 on Ca2+ uptake into the SR and, thereby, on myocardial function.

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