Molecular mechanisms underlying abnormal functions in RyR2 complex in cardiac hypertrophy/heart failure

2型兰尼碱受体（RyR 2）是心肌肌浆网（SR）中的一种Ca^2+释放通道，在调节细胞内Ca^2+浓度中起关键作用。RyR 2与影响RyR 2活性的几种相关蛋白形成多蛋白复合物。在这项研究中，我们研究了在心肌肥厚（CH）/心力衰竭（HF）的动物模型中的RyR 2复合物的异常。从Dahl大鼠（CH/HF模型）分离的心肌细胞的Ca^2+瞬变明显小于对照大鼠。这是由于SR中Ca^2+含量减少所致。在ryanodine结合试验和单通道记录中，Dahl大鼠RyR 2的通道活性高于对照RyR 2。为了解决增加的活性的潜在机制，通过2D电泳确定分离的SR的蛋白质表达谱。与对照大鼠SR相比，Dahl大鼠SR中许多蛋白质减少或增加。我们目前正在通过RNA干扰试验研究几种候选蛋白质的功能。综上所述，这些发现表明蛋白质表达的改变可能导致CH/HF中RyR 2活性的增加，从而导致储存的Ca^2+减少和Ca^2+瞬变减少。

Type 2 ryanodine receptor (RyR2) is a Ca^<2+> release channel in the sarcoplasmic reticulum (SR) in the cardiac muscle and plays a pivotal role in regulation of intracellular Ca^<2+> concentration. RyR2 forms a multi-protein complex with several associated proteins which affect the activity of RyR2. In this study, we examined the abnormality in the RyR2 complex in cardiac hypertrophy (CH)/heart failure (HF) by using animal model. Ca^<2+> transients of the myocytes isolated from the Dahl rats, a model for CH/HF, were significantly smaller than those from the control rats. This was due to a reduced Ca^<2+> content in the SR. The channel activity of Dahl rat RyR2 was higher than the control RyR2 in ryanodine binding assay and single channel recordings. To address the underlying mechanisms of the increased activity, protein expression profiles of the isolated SR were determined by 2D electrophoresis. Many proteins were decreased or increased in the Dahl rat SR in compared with control rat SR. We are currently examining the function of several candidate proteins by RNA interference assay. Taken together, these findings suggest that alterations in the protein expression may cause the increased activity of RyR2 in the CH/HF, which leads to reduction in the stored Ca^<2+> and decreased Ca^<2+> transients.