Dissection of beta-adrenoceptor pathways of ryanodine receptor (RyR2) phosphorylation in the intact rat heart

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

New Orleans, USA

Congreso; Scientific Sessions 2004 American Heart Association; 2004

American Heart Association

Phosphorylation of the Ca-release channels of the cardiac sarcoplasmic reticulum (RyR) 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, b-adrenergic stimulation increased RyR2 phosphorylation at Ser-2809. Although both, PKA and CaMKII pathways, are activated in response to b agonist, no attempts have been made to dissect the kinases involved in the b-adrenergic-induced Ser-2809 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 phospholambam (CaMKII site) by 92.5 " 3.7%, n=6, with no alteration of Ser-16 phosphorylation (PKA site) wich 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 b-adrenergic stimulation.