Ca signaling cross-talk from SR to mitochondria in heart muscle

项目摘要 线粒体和肌浆网(SR)在心肌细胞中形成紧密的界面，其中 钙信号从SR到线粒体的传播有助于生理和心理状态下的心脏功能 病理情况。TRIC是一类新的位于SR的三聚体细胞内阳离子通道 或多种细胞类型的内质网(ER)，它们的功能是反离子通道，允许 钙释放急性期K离子流入SR/ER。基因消融或突变 经络与高血压、心脏病、呼吸缺陷和脆性骨骼有关 疾病。最近蛋白质的晶体结构证实了一个同源三聚体的构型 阳离子通道。在人类和小鼠的基因组中，有两种tre异构体，trc-A和trc-A。 在兴奋性和非兴奋性钙信号调节中显示不同功能的trc-B 细胞。虽然我们过去的研究工作主要集中在了解大脑的生理功能 Tre-A在骨骼肌和平滑肌中的作用，以及在较小程度上在上皮细胞中的作用， TIC在心脏生理学和疾病中的作用在很大程度上尚不清楚。在这里，我们展示了证据 除了调节SR对K离子的渗透性外，TIC-A还起着积分的作用 心肌钙信号生理调控机制的组成部分。我们发现， TRIC-A的羧基-尾部结构域与RyR2通道相互作用，直接调节细胞内钙释放。 高级小鼠出现心律失常、严重的心肌肥大和纤维化。 异丙肾上腺素治疗或横断主动脉缩窄(TAC)手术。隔离TIC-A-/- 心肌细胞显示线粒体功能障碍，这可能反映了肌浆网钙超载引起的 应激条件下线粒体的毒性。由于不受控制的钙释放被认为与 在心脏病理中，线粒体功能障碍，我们假设与RyR2相互作用 调节肌浆网钙的释放和与线粒体的串扰。缺铁性钙导致钙超载 内质网，并对线粒体造成应激诱导的钙毒性。调节失调的SR-线粒体 相声有助于心力衰竭的发展。我们进一步建议将目标对准TICRIC- 介导的SR-线粒体串扰是治疗心血管疾病的新手段 疾病。我们在这个项目中设计的实验包含两个特定的目标：目标1-定义 Trc-A/B和RyR2在调节SR钙信号串扰中的功能相互作用 在生理和病理条件下对心肌细胞线粒体的影响；和目的2-阐明 TRIC-A在体内调节应激诱导的心功能改变中的作用。

Project Summary Mitochondria and sarcoplasmic reticulum (SR) form close interfaces in cardiomyocytes where the propagation of Ca signals from SR to mitochondria contributes to heart function under physiologic and pathologic conditions. TRIC is a novel class of trimeric intracellular cation channels located at the SR or endoplasmic reticulum (ER) of multiple cell types, which function as counter-ion channels that allow flow of K ions into the SR/ER during the acute phase of Ca release. Genetic ablations or mutations of TRIC channels are associated with hypertension, heart disease, respiratory defects and brittle bone disease. The recent crystal structure of TRIC proteins confirms the homotrimeric architecture of a cation channel. Within the human and mouse genomes, there are two TRIC isoforms, TRIC-A and TRIC-B, that display differential functions in regulation of Ca signaling in excitable and non-excitable cells. While our past research efforts primarily focused on understanding the physiological function for TRIC-A in skeletal and smooth muscle and to a lesser extent the role of TRIC-B in epithelial cells, the role of TRIC in cardiac physiology and disease remains largely unexplored. Here we present evidence that TRIC-A, in addition to modulation of the SR permeability to K ions, functions as an integral component of the physiological control mechanism of Ca signaling in cardiac muscle. We found that the carboxyl-tail domain of TRIC-A interacts with the RyR2 channel to directly modulate Ca release from the SR. The TRIC-A-/- mice develop arrhythmia, severe cardiac hypertrophy and fibrosis following isoproterenol treatment or transverse aortic constriction (TAC) surgery. Isolated TRIC-A-/- cardiomtocytes display mitochondria dysfunction that likely reflects SR Ca overload-induced mitochondria toxicity under stress conditions. As uncontrolled Ca release has been implicated in mitochondrial dysfunction in cardiac pathology, we hypothesize that “TRIC interaction with RyR2 modulates SR Ca release and crosstalk with mitochondria. Absence of TRIC leads to Ca overload inside SR and causes stress-induced Ca toxicity to mitochondria. The dysregulated SR-mitochondria crosstalk contributes to the development of heart failure”. We further propose that targeting TRIC- mediated SR-mitochondria crosstalk represents a novel means for treatment of cardiovascular diseases. Our experiments designed in this project contain two specific aims: Aim 1 - to define the functional interaction between TRIC-A/B and RyR2 in regulating the cross-talk of Ca signaling from SR to mitochondria in cardiomyocytes under physiologic and pathologic conditions; and Aim 2 - to elucidate the in vivo role of TRIC-A in mediating stress-induced changes in heart function.