BAG3 regulates contractility and Ca(2+) homeostasis in adult mouse ventricular myocytes.
BAG3 regulates contractility and Ca(2+) homeostasis in adult mouse ventricular myocytes.
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DOI：
10.1016/j.yjmcc.2016.01.015
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发表时间：
2016-03
影响因子：
5
通讯作者：
Cheung JY
中科院分区：
文献类型：
--
作者：
Feldman AM;Gordon J;Wang J;Song J;Zhang XQ;Myers VD;Tilley DG;Gao E;Hoffman NE;Tomar D;Madesh M;Rabinowitz J;Koch WJ;Su F;Khalili K;Cheung JY
Bcl 2相关的产气基因3（BAG 3）是在心脏中组成性表达的575个氨基酸的抗凋亡蛋白。BAG 3突变，包括导致蛋白质丢失的突变，与家族性心肌病相关。此外，已发现终末期非家族性心肌衰竭中的BAG 3水平降低。与新生肌细胞中发现的BAG 3在细胞质中并参与蛋白质质量控制和细胞凋亡相反，在成年小鼠左心室（LV）肌细胞中，BAG 3与肌膜和t-小管中的Na+-K+-ATP酶和L-型Ca 2+通道共定位。BAG 3与β1-肾上腺素能受体、L-型钙通道和磷膜蛋白共沉淀。为了模拟在人类心力衰竭中观察到的BAG 3蛋白水平降低，我们在成人LV肌细胞中通过shRNA（shBAG 3）靶向BAG 3。将BAG 3减少55%导致异丙肾上腺素刺激的LV肌细胞收缩和[Ca 2 +]i瞬时振幅降低。异丙肾上腺素处理的shBAG 3心肌细胞中L型Ca 2+电流（伊卡）和肌浆网（SR）Ca 2+含量减少，但Na+/Ca 2+交换电流（INaCa）或SR Ca 2+摄取不减少。毛喉素或二丁酰cAMP使shBAG 3肌细胞中的伊卡振幅恢复到WT肌细胞中观察到的振幅，这与BAG 3在受体上游和受体水平上具有作用一致。静息膜电位和动作电位振幅不受影响，但APD 50和APD 90延长shBAG 3心肌细胞。在BAG 3较低的心肌细胞中，Ca 2+进入分子和其他重要的兴奋-收缩蛋白的蛋白水平没有变化。我们的研究发现，BAG 3定位于肌膜和t-小管，同时通过与β1-肾上腺素能受体和L-型Ca 2+通道的特异性相互作用调节肌细胞收缩和动作电位时程，这为BAG 3在心肌病中的作用和心力衰竭中心律失常风险增加提供了新的见解。
Bcl2-associated athanogene 3 (BAG3) is a 575 amino acid anti-apoptotic protein that is constitutively expressed in the heart. BAG3 mutations, including mutations leading to loss of protein, are associated with familial cardiomyopathy. Furthermore, BAG3 levels have been found to be reduced in end-stage non-familial failing myocardium. In contrast to neonatal myocytes in which BAG3 is found in the cytoplasm and involved in protein quality control and apoptosis, in adult mouse left ventricular (LV) myocytes BAG3 co-localized with Na+-K+-ATPase and L-type Ca2+ channels in the sarcolemma and t-tubules. BAG3 co-immunoprecipitated with β1-adrenergic receptor, L-type Ca2+ channels and phospholemman. To simulate decreased BAG3 protein levels observed in human heart failure, we targeted BAG3 by shRNA (shBAG3) in adult LV myocytes. Reducing BAG3 by 55% resulted in reduced contraction and [Ca2+]i transient amplitudes in LV myocytes stimulated with isoproterenol. L-type Ca2+ current (ICa) and sarcoplasmic reticulum (SR) Ca2+ content but not Na+/Ca2+ exchange current (INaCa) or SR Ca2+ uptake were reduced in isoproterenol-treated shBAG3 myocytes. Forskolin or dibutyrl cAMP restored ICa amplitude in shBAG3 myocytes to that observed in WT myocytes, consistent with BAG3 having effects upstream and at the level of the receptor. Resting membrane potential and action potential amplitude were unaffected but APD50 and APD90 were prolonged in shBAG3 myocytes. Protein levels of Ca2+ entry molecules and other important excitation-contraction proteins were unchanged in myocytes with lower BAG3. Our findings that BAG3 is localized at the sarcolemma and t-tubules while modulating myocyte contraction and action potential duration through specific interaction with the β1-adrenergic receptor and L-type Ca2+ channel provide novel insight into the role of BAG3 in cardiomyopathies and increased arrhythmia risks in heart failure.