%0 Journal Article %1 Maac_2005_91 %A Maack, Christoph %A Ganesan, Anand %A Sidor, Agnieszka %A O'Rourke, Brian %D 2005 %J Circ. Res. %K 15550690 4,5-Diphosphate, Acid Action Adenocarcinoma, Adenoviridae, Allosteric Amino Animals, Calcium, Cardiac, Cell Data, Deletion, Exchanger, Extramural, Fusion Genetic Gov't, Guinea Humans, Interaction Kidney, Line, Lung Mapping, Molecular Motifs, Mutagenesis, Myocytes, N.I.H., Neoplasms, Non-U.S. P.H.S., Patch-Clamp Peptides, Phosphatidylinositol Pigs, Potentials, Protein Proteins, Recombinant Regulation, Research Sarcolemma, Sequence Sequence, Site-Directed, Sodium, Sodium-Calcium Structure, Support, Techniques, Tertiary, Tumor, U.S. Vectors, %N 1 %P 91--99 %R 10.1161/01.RES.0000151334.48676.68 %T Cardiac sodium-calcium exchanger is regulated by allosteric calcium and exchanger inhibitory peptide at distinct sites. %U http://dx.doi.org/10.1161/01.RES.0000151334.48676.68 %V 96 %X The sarcolemmal Na$^+$-Ca$^2+$ exchanger (NCX) is the main Ca$^2+$ extrusion mechanism in cardiac myocytes and is thus essential for the regulation of Ca$^2+$ homeostasis and contractile function. A cytosolic region (f-loop) of the protein mediates regulation of NCX function by intracellular factors including inhibition by exchanger inhibitory peptide (XIP), a 20 amino acid peptide matching the sequence of an autoinhibitory region involved in allosteric regulation of NCX by intracellular Na$^+$, Ca$^2+$, and phosphatidylinositol-4,5-biphosphate (PIP2). Previous evidence indicates that the XIP interaction domain can be eliminated by large deletions of the f-loop that also remove activation of NCX by intracellular Ca$^2+$. By whole-cell voltage clamping experiments, we demonstrate that deletion of residues 562-679, but not 440- 456, 498-510, or 680-685 of the f-loop selectively eliminates XIP-mediated inhibition of NCX expressed either heterologously (HEK293 and A549 cells) or in guinea pig cardiac myocytes. In contrast, by plotting I(NCX) against reverse-mode NCX-mediated Ca$^2+$ transients in myocytes, we demonstrate that Ca$^2+$-dependent regulation of NCX is preserved in Delta562-679, but significantly reduced in the other three deletion mutants. The findings indicate that f-loop residues 562-679 may contain the regulatory site for endogenous XIP, but this site is distinct from the Ca$^2+$-regulatory domains of the NCX. Because regulation of the NCX by Na$^+$ and PIP2 involves the endogenous XIP region, the Delta562-679 mutant NCX may be a useful tool to investigate this regulation in the context of the whole cardiac myocyte.

@article{Maac_2005_91, abstract = {The sarcolemmal {N}a$^{+}$-{C}a$^{2+}$ exchanger (NCX) is the main {C}a$^{2+}$ extrusion mechanism in cardiac myocytes and is thus essential for the regulation of {C}a$^{2+}$ homeostasis and contractile function. A cytosolic region (f-loop) of the protein mediates regulation of NCX function by intracellular factors including inhibition by exchanger inhibitory peptide ({XIP}), a 20 amino acid peptide matching the sequence of an autoinhibitory region involved in allosteric regulation of NCX by intracellular {N}a$^{+}$, {C}a$^{2+}$, and phosphatidylinositol-4,5-biphosphate ({PIP}2). Previous evidence indicates that the {XIP} interaction domain can be eliminated by large deletions of the f-loop that also remove activation of NCX by intracellular {C}a$^{2+}$. By whole-cell voltage clamping experiments, we demonstrate that deletion of residues 562-679, but not 440- 456, 498-510, or 680-685 of the f-loop selectively eliminates {XIP}-mediated inhibition of NCX expressed either heterologously (HEK293 and A549 cells) or in guinea pig cardiac myocytes. In contrast, by plotting I(NCX) against reverse-mode NCX-mediated {C}a$^{2+}$ transients in myocytes, we demonstrate that {C}a$^{2+}$-dependent regulation of NCX is preserved in Delta562-679, but significantly reduced in the other three deletion mutants. The findings indicate that f-loop residues 562-679 may contain the regulatory site for endogenous {XIP}, but this site is distinct from the {C}a$^{2+}$-regulatory domains of the NCX. Because regulation of the NCX by {N}a$^{+}$ and {PIP}2 involves the endogenous {XIP} region, the Delta562-679 mutant NCX may be a useful tool to investigate this regulation in the context of the whole cardiac myocyte.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Maack, Christoph and Ganesan, Anand and Sidor, Agnieszka and O'Rourke, Brian}, biburl = {https://www.bibsonomy.org/bibtex/2df1b3be86ce2db850ceb6fc2241436f9/hake}, description = {The whole bibliography file I use.}, doi = {10.1161/01.RES.0000151334.48676.68}, file = {Maac_2005_91.pdf:Maac_2005_91.pdf:PDF}, interhash = {d1ecaa2ed93954355347856296292abe}, intrahash = {df1b3be86ce2db850ceb6fc2241436f9}, journal = {Circ. Res.}, keywords = {15550690 4,5-Diphosphate, Acid Action Adenocarcinoma, Adenoviridae, Allosteric Amino Animals, Calcium, Cardiac, Cell Data, Deletion, Exchanger, Extramural, Fusion Genetic Gov't, Guinea Humans, Interaction Kidney, Line, Lung Mapping, Molecular Motifs, Mutagenesis, Myocytes, N.I.H., Neoplasms, Non-U.S. P.H.S., Patch-Clamp Peptides, Phosphatidylinositol Pigs, Potentials, Protein Proteins, Recombinant Regulation, Research Sarcolemma, Sequence Sequence, Site-Directed, Sodium, Sodium-Calcium Structure, Support, Techniques, Tertiary, Tumor, U.S. Vectors,}, month = Jan, number = 1, pages = {91--99}, pii = {01.RES.0000151334.48676.68}, pmid = {15550690}, timestamp = {2009-06-03T11:21:21.000+0200}, title = {Cardiac sodium-calcium exchanger is regulated by allosteric calcium and exchanger inhibitory peptide at distinct sites.}, url = {http://dx.doi.org/10.1161/01.RES.0000151334.48676.68}, volume = 96, year = 2005 }