Dissection of beta-adrenoceptor pathways of ryanodine receptor (RyR2) phosphorylation in the intact Heart.

MATTIAZZI A, SAID M, FERRERO P, VITTONE L, MUNDIÑA-WEILENMANN C.

New Orleans

Congreso; Scientific Session 2004, American Heart Association; 2004

American Heart Association

Meeting: Scientific Sessions 2004 Session Number: AOP.19.1N Session Title: Thomas Smith Memorial Lecture: Molecular Regulation of EC Coupling Presentation Number: 619 Presentation Title: Dissection of ß-adrenoceptor pathways of ryanodine receptor (RyR2) phosphorylation in the intact rat heart Author Block: Alicia Mattiazzi, Matilde Said, Paola Ferrero, Leticia Vittone, Cecilia Mundina-Weilenmann, Ctr Investigaciones Cardiovasculares, La Plata, Argentina Disclosure Block:  A. Mattiazzi, None; M. Said, None; P. Ferrero, None; L. Vittone, None; C. Mundina-Weilenmann, None. Abstract Body: Phosphorylation of the Ca-release channels of the cardiac sarcoplasmic reticulum (RyR2) has been shown to modulate the channel activity. A Ser-2809 in RyR2, has been described as the phosphorylation site for both PKA and CaMKII. In the intact heart, ß-adrenergic stimulation increased RyR2 phosphorylation at Ser-2809. Although both, PKA and CaMKII pathways, are activated in response to ß agonists, no attempts have been made to dissect the kinases involved in the ß-adrenergic-induced Ser-2809 RyR2 phosphorylation. To clarify this issue, rat hearts were perfused with isoproterenol (Iso) in the absence and the presence of low [Ca] plus nifedipine, to inhibit the CaMKII pathway. The figure shows the mirror image of the phosphorylated (PS2809-RyR2) and dephosphorylated (dePS2809-RyR2) Ser-2809 residue, assessed by phosphorylation-state dependent antibodies. Perfusion of Iso in the presence of low [Ca] plus nifedipine, significantly decreased the phosphorylation of Ser-2809 induced by Iso. The same maneuver produced a significant decrease in the Iso-induced Thr-17 phosphorylation of phospholamban (CaMKII site) by 92.5 ± 3.7%, n=6, with no alteration of Ser-16 phosphorylation (PKA site), which confirms the ability of low [Ca] treatment to decrease CaMKII activity against other targets. The results indicate that RyR2 is phosphorylated at the Ser-2809 site by CaMKII and PKA in response to ß-adrenergic stimulation.