title: Regulation of sodium-calcium exchanger activity by creatine kinase under energy-compromised conditions.
abstract: Na(+)/Ca(2+) exchanger (NCX) is one of the major mechanisms for removing Ca(2+) from the cytosol especially in cardiac myocytes and neurons, where their physiological activities are triggered by an influx of Ca(2+). NCX contains a large intracellular loop (NCXIL) that is responsible for regulating NCX activity. Recent evidence has shown that proteins, including kinases and phosphatases, associate with NCX1IL to form a NCX1 macromolecular complex. To search for the molecules that interact with NCX1IL and regulate NCX1 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. Moreover, both sMiCK and the muscle-type creatine kinase (CKM) coimmunoprecipitated with NCX1 using lysates of cardiacmyocytes and HEK293T cells that transiently expressed NCX1 and various creatine kinases. 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 autophosphorylation and the catalytic activity of sMiCK and CKM are not required for their regulation of NCX1 activity. Our results suggest a novel mechanism for the regulation of NCX1 activity.
authors.affiliation: Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 112, Taiwan, Republic of China.
authors.forename: Ya-Chi
authors.initials: YC
authors.lastname: Yang
authors.forename: Ming-Ji
authors.initials: MJ
authors.lastname: Fann
authors.forename: Wen-Hsin
authors.initials: WH
authors.lastname: Chang
authors.forename: Long-Hao
authors.initials: LH
authors.lastname: Tai
authors.forename: Jhih-Hang
authors.initials: JH
authors.lastname: Jiang
authors.forename: Lung-Sen
authors.initials: LS
authors.lastname: Kao
mesh_terms: D000818:Animals; D002417:Cattle; D002460:Cell Line; D003402:Creatine Kinase / Q000737:chemistry / Q000378:metabolism*; D052283:Creatine Kinase, MM Form / Q000737:chemistry / Q000378:metabolism; D052281:Creatine Kinase, Mitochondrial Form / Q000737:chemistry / Q000378:metabolism; D004734:Energy Metabolism; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D021381:Protein Transport; D012518:Sarcomeres / Q000201:enzymology; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D007527:Isoenzymes; D019831:Sodium-Calcium Exchanger; C110374:sodium-calcium exchanger 1; D011493:Protein Kinase C; D003402:Creatine Kinase; D052283:Creatine Kinase, MM Form; D052281:Creatine Kinase, Mitochondrial Form