Study on regulatory mechanism for cardiac contraction : seeking for therapeutic basis of heart failure.

该项目的目的是为心力衰竭的治疗基础开辟一个新的概念。从1998年到2000年的三年时间里，我们围绕心力衰竭早期心脏E-C偶联的钙通道信号、心肌抗缺血的分子基础、L钙通道门控调控的分子机制、β肾上腺素能受体脱敏的细胞机制等方面进行了研究。1)在心肌缺血保护的分子基础方面，我们发现ROS直接激活GI和GO，进而激活ERK(细胞外信号调节激酶)。我们提出了一个新的概念，即ROS也参与了导致心脏保护的信号转导途径。2)通过比较海洋动物L型钙通道α_1亚基和敏感哺乳动物α_2+gt；通道α_1亚基的氨基酸序列，确定DHP敏感的哺乳动物DHP通道1C_1亚基与DHP敏感的哺乳动物DHP通道1C_1亚基的氨基酸序列比较表明，SER1115是DHP敏感的哺乳动物DHP通道亚基与DHP不敏感的Ca_1亚基调控L通道门控的关键决定因素。我们的发现为电压依赖性钙通道的门控机制提供了一个新的概念。我们还发现，位于L型钙通道α_1C亚基羧基末端的Ser1901是PKA调节的靶点。3)我们发现，在心力衰竭的早期适应阶段，冠状动脉结扎模型大鼠的心室肌细胞内钙离子交换活性上调。4)阐明了β_1受体耐受β肾上腺素能激动剂内化的分子基础，这部分解释了β_1肾上腺素能受体下调速率较慢的原因。

The aim of this project was to open up a novel concept for therapeutic basis of heart failure. In the past three years from 1998 through 2000, we have carried out the research project by focusing on Ca^<2+> signaling in cardiac E-C coupling at the early stage of heart failure, molecular basis for cardiac protection against ischemia, molecular mechanism underlying modulation of L-type Ca^<2+> channel gating, cellular mechanism for desensitization of β adrenergic receptors. Our research products are summarized as follows :1) With respect to the molecular basis for cardiac protection against ischemia, we found that ROS (reactive oxygen species) directly activates Gi and Go, which results in the activation of ERK (extracellular signal-regulated kinase). We opened up a novel concept that ROS is also involved in the signal transduction pathway leading to cardiac protection. 2) We identified Ser1115 in the pore domain of L-type Ca^<2+> channel α_<1C> subunit as the critical determinant for modulation of L-type Ca^<2+> channel gating by Ca^<2+> channel agonists by comparing the amino acid sequences between DHP-sensitive mammalian α_<1C> subunit and DHP-insensitive Ca^<2+> channel α_1 subunit of sea animals. Our finding opened up a novel concept in the gating mechanism of voltage-dependent Ca^<2+> channels. We also found that Ser1901 in the carboxy terminal of L-type Ca^<2+> channel α_<1C> subunit is the target for the PKA-modulation. 3) We found that, in the early adaptive stage of heart failure, the Ca^<2+> handling mechanism, especially Na^<+-> Ca^<2+> exchange activity, is up-regulated in ventricular myocytes of coronary artery ligation model rats. 4) We clarified the molecular basis for the tolerance of β_1 adrenergic receptors against internalization on exposure to β adrenergic agonists, which partially explains the reason for the slower rate of down regulation β_1 adrenergic receptors.