Ischemia-reperfusion (I/R) reveals differential regulation in the phosphorylation of Ser-2809 site of the ryanodyne receptor (RyR2) and phospholamban (PLN) phosphorylaiton sites

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

New Orleans, USA

Congreso; Scientific Sessions 2004 American Heart Association; 2004

American Heart Association

The Ca release channel of the sarcoplasmic reticulum (RyR2) is susceptible of phosphorylation by PKA and CaMKII at the Ser-2809 site. We previously showed that the phosphorylation of Ser-16 (PKA site) and Thr-17 (CaMKII site) of PLN, increased at different times during I/R, indicating increased PKA and CaMKII activities. The phosphorylation of Ser-2809 of RyR2 was assessed by immunodetection during l/R. Ser-2809 phosphorylation significantly decreased at 20min of ischernia (l20) and at 1 and 5 min of reperfusion (R1 and R5), returning to pre-ischemic levels (Pl) at R15 (Figure, A). This occurred in spite of the significant increase in the phosphorylation of PLN sites, Ser-16 at l20 and Thr-17 at R1, measured simultaneously (96.3 " 22 9 % and 124.5 " 24.7 %, respectively, above Pl). A possible clue to explain these results, may lie in the different activities of the phosphatases that regulate the phosphorylation level of these proteins, during I/R. While PLN is mainly dephosphorylated by PP1, the RyR2 is also associated to other phosphatases, like PP2A. Acidosis, a condition present during I and early R, inhibits PP1 but increases PP2A activity (Figure, B). The results show for the first time the time course of Ser-2809 of RyR2 during I/R and reveal a differential modulation of the phosphorylation of PLN and RyR2 during I/R. It is suggested that an increase PP2A activity may be partially responsible for the decreased phosphorylation level of RyR2. This decrease may contribute to the altered Ca handling of I/R injury.