Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan, Republic of China.
Adv Exp Med Biol. 2013;961:163-73. doi: 10.1007/978-1-4614-4756-6_14.
It has been shown that in rat heart NCX1 exists in a macromolecular -complex including PKA, PKA-anchoring protein, PKC, and phosphatases PP1 and PP2A. In addition, several lines of evidence suggest that the interactions of the exchanger with other molecules are closely associated with its function in regulation of Ca(2+). NCX contains a large intracellular loop (NCXIL) that is responsible for regulating NCX activity. We used the yeast two-hybrid method to screen a human heart cDNA library and found that the C-terminal region of sarcomeric mitochondrial creatine kinase (sMiCK) interacted with NCX1IL. Among the four creatine kinase (CK) isozymes, both sMiCK and the muscle-type cytosolic creatine kinase (CKM) co-immunoprecipitated with NCX1. Both sMiCK and CKM were able to produce a recovery in the decreased NCX1 activity that was lost under energy-compromised conditions. This regulation is mediated through a putative PKC phosphorylation site of sMiCK and CKM. The catalytic activity of sMiCK and CKM is not required for their regulation of NCX1 activity. Our results suggest a novel mechanism for the regulation of NCX1 activity and a novel role for CK.
已有研究表明，在大鼠心脏中，NCX1 存在于一个包含 PKA、PKA 锚定蛋白、PKC 和磷酸酶 PP1 和 PP2A 的大分子复合物中。此外，有几条证据表明，交换器与其他分子的相互作用与其在调节[Ca（2+）]（i）中的功能密切相关。NCX 包含一个大的细胞内环（NCXIL），负责调节 NCX 的活性。我们使用酵母双杂交方法筛选了人类心脏 cDNA 文库，发现肌小节线粒体肌酸激酶（sMiCK）的 C 端区域与 NCX1IL 相互作用。在四种肌酸激酶（CK）同工酶中，sMiCK 和肌型细胞质肌酸激酶（CKM）都与 NCX1 共免疫沉淀。sMiCK 和 CKM 都能够恢复在能量受限条件下丧失的降低的 NCX1 活性。这种调节是通过 sMiCK 和 CKM 的一个假定的 PKC 磷酸化位点介导的。sMiCK 和 CKM 的催化活性对于其对 NCX1 活性的调节不是必需的。我们的结果表明了一种调节 NCX1 活性的新机制和 CK 的新作用。
