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.
%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
}