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， Ca信号从SR到线粒体的传播有助于生理和生理条件下的心脏功能， 病理条件。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），其功能是反离子通道， 在Ca释放的急性期，K离子流入SR/ER。基因消融或突变 TRIC通道与高血压、心脏病、呼吸缺陷和骨质疏松有关 疾病TRIC蛋白的最新晶体结构证实了TRIC蛋白的同源三聚体结构。 阳离子通道在人类和小鼠基因组中，存在两种TRIC同种型，TRIC-A和TRIC-B。 TRIC-B在兴奋性和非兴奋性细胞中对Ca信号的调节作用不同。 细胞虽然我们过去的研究工作主要集中在了解生理功能， TRIC-A在骨骼肌和平滑肌中的作用以及TRIC-B在上皮细胞中的作用， TRIC在心脏生理学和疾病中的作用仍在很大程度上未被探索。在这里我们提出证据 TRIC-A除了调节SR对K离子的渗透性外，还起着积分作用， 心肌钙信号生理控制机制的组成部分。我们发现 TRIC-A的羧基尾部结构域与RyR 2通道相互作用，直接调节Ca从 Sr. TRIC-A-/-小鼠在给药后发生心律失常、严重的心脏肥大和纤维化。 异丙肾上腺素治疗或横向主动脉缩窄（TAC）手术。隔离TRIC-A-/- 心肌细胞显示线粒体功能障碍，这可能反映了SR Ca超载诱导的 应激条件下的线粒体毒性。由于不受控制的钙释放与 在心脏病理学中，我们假设“TRIC与RyR 2的相互作用 调节SR Ca释放和与线粒体的串扰。缺乏TRIC导致Ca超载 并导致应激诱导的线粒体钙毒性。SR线粒体失调 串话导致心力衰竭的发展”。我们进一步建议，针对TRIC- 介导的SR-线粒体串扰代表了治疗心血管疾病的新方法， 疾病我们在这个项目中设计的实验包含两个具体目标：目标1 -定义 TRIC-A/B与RyR 2在调节SR钙信号转导中的相互作用 在生理和病理条件下心肌细胞中的线粒体;目的2 -阐明 TRIC-A在介导应激诱导的心脏功能变化中的体内作用。

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.