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

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

New Orleans

Congreso; Scientific Sessions 2004, American Heart Association; 2004

American Heart Association

Meeting: Scientific Sessions 2004 Session Number: APS.19.1 Session Title: Cellular Aspects of Excitation-Contraction Coupling Presentation Number: 937 Presentation Title: Ischemia-reperfusion (I/R) reveals differential regulation in the phosphorylation of Ser-2809 site of the ryanodyne receptor (RyR2) and phospholamban (PLN) phosphorylation sites Author Block: Cecilia Mundina-Weilenmann, Paola Ferrero, Matilde Said, Leticia Vittone, Alicia Mattiazzi, Ctr Investigaciones Cardiovasculares, La Plata, Argentina Disclosure Block:  C. Mundina-Weilenmann, None; P. Ferrero, None; M. Said, None; L. Vittone, None; A. Mattiazzi, None. Abstract Body: 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 I/R. Ser-2809 phosphorylation significantly decreased at 20min of ischemia (I20) and at 1 and 5 min of reperfusion (R1 and R5), returning to pre-ischemic levels (PI) at R15 (Figure, A). This occurred in spite of the significant increase in the phosphorylation of PLN sites, Ser-16 at I20 and Thr-17 at R1, measured simultaneously (96.3 ± 22.9 % and 124.5 ± 24.7 %, respectively, above PI). 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.