Molecular determinants of altered Ca2+ handling in human chronic atrial fibrillation.

TY - JOUR

T1 - Molecular determinants of altered Ca2+ handling in human chronic atrial fibrillation.

AU - El-Armouche, Ali

AU - Boknik, Peter

AU - Eschenhagen, Thomas

AU - Carrier, Lucie

AU - Knaut, Michael

AU - Ravens, Ursula

AU - Dobrev, Dobromir

PY - 2006

Y1 - 2006

N2 - BACKGROUND: Abnormal Ca2+ handling may contribute to impaired atrial contractility and arrhythmogenesis in human chronic atrial fibrillation (cAF). Here, we assessed the phosphorylation levels of key proteins involved in altered Ca2+ handling and contractility in cAF patients. METHODS AND RESULTS: Total and phosphorylation levels of Ca2+-handling and myofilament proteins were analyzed by Western blotting in right atrial appendages of 49 patients in sinus rhythm and 52 cAF patients. We found a higher total activity of type 1 (PP1) and type 2A phosphatases in cAF, which was associated with inhomogeneous changes of protein phosphorylation in the cellular compartments, ie, lower protein kinase A (PKA) phosphorylation of myosin binding protein-C (Ser-282 site) at the thick myofilaments but preserved PKA phosphorylation of troponin I at the thin myofilaments and enhanced PKA (Ser-16 site) and Ca2+-calmodulin protein kinase (Thr-17 site) phosphorylation of phospholamban. PP1 activity at sarcoplasmic reticulum is controlled by inhibitor-1 (I-1), which blocks PP1 in its PKA-phosphorylated form only. In cAF, the ratio of Thr-35-phosphorylated to total I-1 was 10-fold higher, which suggests that the enhanced phosphorylation of phospholamban may result from a stronger PP1 inhibition by PKA-hyperphosphorylated (activated) I-1. CONCLUSIONS: Altered Ca2+ handling in cAF is associated with impaired phosphorylation of myosin binding protein-C, which may contribute to the contractile dysfunction after cardioversion. The hyperphosphorylation of phospholamban probably results from enhanced inhibition of sarcoplasmic PP1 by hyperphosphorylated I-1 and may reinforce the leakiness of ryanodine channels in cAF. Restoration of sarcoplasmic reticulum-associated PP1 function may represent a new therapeutic option for treatment of atrial fibrillation.

AB - BACKGROUND: Abnormal Ca2+ handling may contribute to impaired atrial contractility and arrhythmogenesis in human chronic atrial fibrillation (cAF). Here, we assessed the phosphorylation levels of key proteins involved in altered Ca2+ handling and contractility in cAF patients. METHODS AND RESULTS: Total and phosphorylation levels of Ca2+-handling and myofilament proteins were analyzed by Western blotting in right atrial appendages of 49 patients in sinus rhythm and 52 cAF patients. We found a higher total activity of type 1 (PP1) and type 2A phosphatases in cAF, which was associated with inhomogeneous changes of protein phosphorylation in the cellular compartments, ie, lower protein kinase A (PKA) phosphorylation of myosin binding protein-C (Ser-282 site) at the thick myofilaments but preserved PKA phosphorylation of troponin I at the thin myofilaments and enhanced PKA (Ser-16 site) and Ca2+-calmodulin protein kinase (Thr-17 site) phosphorylation of phospholamban. PP1 activity at sarcoplasmic reticulum is controlled by inhibitor-1 (I-1), which blocks PP1 in its PKA-phosphorylated form only. In cAF, the ratio of Thr-35-phosphorylated to total I-1 was 10-fold higher, which suggests that the enhanced phosphorylation of phospholamban may result from a stronger PP1 inhibition by PKA-hyperphosphorylated (activated) I-1. CONCLUSIONS: Altered Ca2+ handling in cAF is associated with impaired phosphorylation of myosin binding protein-C, which may contribute to the contractile dysfunction after cardioversion. The hyperphosphorylation of phospholamban probably results from enhanced inhibition of sarcoplasmic PP1 by hyperphosphorylated I-1 and may reinforce the leakiness of ryanodine channels in cAF. Restoration of sarcoplasmic reticulum-associated PP1 function may represent a new therapeutic option for treatment of atrial fibrillation.

M3 - SCORING: Zeitschriftenaufsatz

VL - 114

SP - 670

EP - 680

JO - CIRCULATION

JF - CIRCULATION

SN - 0009-7322

IS - 7

M1 - 7

ER -