PHOSPHORYLATIONS OF PHOSPHOLAMBAN RESIDUES ARE critical in ischemic-reperfusion recovery in mice hearts

VALVERDE CA; MASINE L; KRANIAS EG; REYES M; MATTIAZZI A; ESCOBAR AL

Long Beach, California, USA

Congreso; 49th Annual Meeting of the Biophysical Society; 2005

Biophysical Society

Phosphorylation of phospholamban (PLN) at Ser16 (PKA site) and at Thr17 (CaMKII site), increases sarcoplasmic reticulum Ca2+ uptake, and myocardial contractility and relaxation. Previous experiments in transgenic mice expressing wild type PLN (PLN-WT), or PLN mutants in which either Thr17 or Ser16 were replaced by Ala into the PLN null background, demonstrated that both PLN phosphorylation sites were involved in the mechanical recovery after a period of ischemia. To further explore this issue, the present experiments were undertaken to assess the time course of both the intracellular calcium transients and the left ventricular pressure in the intact heart of PLN double mutant mice (PLN-DM), (where both phosphorylation sites were replaced by Ala). The hearts were evaluated with a protocol of ischemia/reperfusion (12/30 min). Briefly, hearts from transgenic mice were mounted on a Langendorff apparatus positioned on a Pulsed Local Field Fluorescence microscope and loaded with the calcium indicator Rhod-2. Ventricular pressure was measured with home made balloon connected to a pressure sensor (Motorola, CA). Both the amplitude of the developed pressure and the transient change of intracellular calcium concentration are highly diminished in the PLN-DM in comparison with PLN-WT after the reperfusion. Interestingly, the diastolic pressure is much higher in PLN-DM in comparison with PLN-WT after the reperfusion.