|
|
|
|
|
|
|
||
Original Article |
lhryshko{at}sbrc.umanitoba.ca
Ion transport and regulation of Na+–Ca2+ exchange were examined for two alternatively spliced isoforms of the canine cardiac Na+–Ca2+ exchanger, NCX1.1, to assess the role(s) of the mutually exclusive A and B exons. The exchangers examined, NCX1.3 and NCX1.4, are commonly referred to as the kidney and brain splice variants and differ only in the expression of the BD or AD exons, respectively. Outward Na+–Ca2+ exchange activity was assessed in giant, excised membrane patches from Xenopus laevis oocytes expressing the cloned exchangers, and the characteristics of Na+i- (i.e., I1) and Ca2+i- (i.e., I2) dependent regulation of exchange currents were examined using a variety of experimental protocols. No remarkable differences were observed in the current–voltage relationships of NCX1.3 and NCX1.4, whereas these isoforms differed appreciably in terms of their I1 and I2 regulatory properties. Sodium-dependent inactivation of NCX1.3 was considerably more pronounced than that of NCX1.4 and resulted in nearly complete inhibition of steady state currents. This novel feature could be abolished by proteolysis with
-chymotrypsin. It appears that expression of the B exon in NCX1.3 imparts a substantially more stable I1 inactive state of the exchanger than does the A exon of NCX1.4. With respect to I2 regulation, significant differences were also found between NCX1.3 and NCX1.4. While both exchangers were stimulated by low concentrations of regulatory Ca2+i, NCX1.3 showed a prominent decrease at higher concentrations (>1 µM). This does not appear to be due solely to competition between Ca2+i and Na+i at the transport site, as the Ca2+i affinities of inward currents were nearly identical between the two exchangers. Furthermore, regulatory Ca2+i had only modest effects on Na+i-dependent inactivation of NCX1.3, whereas I1 inactivation of NCX1.4 could be completely eliminated by Ca2+i. Our results establish an important role for the mutually exclusive A and B exons of NCX1 in modulating the characteristics of ionic regulation and provide insight into how alternative splicing tailors the regulatory properties of Na+–Ca2+ exchange to fulfill tissue-specific requirements of Ca2+ homeostasis.
Key Words: sodium–calcium exchange • regulation • alternative splicing
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  M. Hilge, J. Aelen, A. Foarce, A. Perrakis, and G. W. Vuister Ca2+ regulation in the Na+/Ca2+ exchanger features a dual electrostatic switch mechanism PNAS, August 25, 2009; 106(34): 14333 - 14338. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 V. Chaptal, M. Ottolia, G. Mercado-Besserer, D. A. Nicoll, K. D. Philipson, and J. Abramson Structure and Functional Analysis of a Ca2+ Sensor Mutant of the Na+/Ca2+ Exchanger J. Biol. Chem., May 29, 2009; 284(22): 14688 - 14692. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Boyman, H. Mikhasenko, R. Hiller, and D. Khananshvili Kinetic and Equilibrium Properties of Regulatory Calcium Sensors of NCX1 Protein J. Biol. Chem., March 6, 2009; 284(10): 6185 - 6193. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Hryshko What regulates Na+/Ca2+ exchange? Focus on "Sodium-dependent inactivation of sodium/calcium exchange in transfected Chinese hamster ovary cells" Am J Physiol Cell Physiol, October 1, 2008; 295(4): C869 - C871. [Full Text] [PDF]
|
|
|
|
 |
|
 J. Tian and Z.-j. Xie The Na-K-ATPase and Calcium-Signaling Microdomains Physiology, August 1, 2008; 23(4): 205 - 211. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. M. Besserer, M. Ottolia, D. A. Nicoll, V. Chaptal, D. Cascio, K. D. Philipson, and J. Abramson From the Cover: The second Ca2+-binding domain of the Na+ Ca2+ exchanger is essential for regulation: Crystal structures and mutational analysis PNAS, November 20, 2007; 104(47): 18467 - 18472. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. P. Blaustein, T. H. Charpentier, and D. J. Weber Getting a grip on calcium regulation PNAS, November 20, 2007; 104(47): 18349 - 18350. [Full Text] [PDF]
|
|
|
|
|
|
F. Visser and J. Lytton K+-Dependent Na+/Ca2+ Exchangers: Key Contributors to Ca2+ Signaling Physiology, June 1, 2007; 22(3): 185 - 192. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. P. Ander, C. Hurtado, C. S. Raposo, T. G. Maddaford, J. F. Deniset, L. V. Hryshko, G. N. Pierce, and A. Lukas Differential sensitivities of the NCX1.1 and NCX1.3 isoforms of the Na+-Ca2+ exchanger to {alpha}-linolenic acid Cardiovasc Res, January 15, 2007; 73(2): 395 - 403. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Hurtado, M. Prociuk, T. G. Maddaford, E. Dibrov, N. Mesaeli, L. V. Hryshko, and G. N. Pierce Cells expressing unique Na+/Ca2+ exchange (NCX1) splice variants exhibit different susceptibilities to Ca2+ overload Am J Physiol Heart Circ Physiol, May 1, 2006; 290(5): H2155 - H2162. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Omelchenko, R. Bouchard, S. Shurraw, M. Trac, M. Hnatowich, and L. V. Hryshko Frequency-dependent regulation of cardiac Na+/Ca2+ exchanger Am J Physiol Heart Circ Physiol, October 1, 2005; 289(4): H1594 - H1603. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. R. Marshall, T.-C. Pan, H. D. Le, A. Omelchenko, P. P. Hwang, L. V. Hryshko, and G. F. Tibbits cDNA Cloning and Expression of the Cardiac Na+/Ca2+ Exchanger from Mozambique Tilapia (Oreochromis mossambicus) Reveal a Teleost Membrane Transporter with Mammalian Temperature Dependence J. Biol. Chem., August 12, 2005; 280(32): 28903 - 28911. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
X. Cai and J. Lytton Molecular Cloning of a Sixth Member of the K+-dependent Na+/Ca2+ Exchanger Gene Family, NCKX6 J. Biol. Chem., February 13, 2004; 279(7): 5867 - 5876. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Omelchenko, R. Bouchard, H. D. Le, P. Choptiany, N. Visen, M. Hnatowich, and L. V. Hryshko Inhibition of Canine (NCX1.1) and Drosophila (CALX1.1) Na+-Ca2+ Exchangers by 7-Chloro-3,5-dihydro-5-phenyl-1H-4,1-benzothiazepine-2-one (CGP-37157) J. Pharmacol. Exp. Ther., September 1, 2003; 306(3): 1050 - 1057. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Dunn, C. L. Elias, H. D. Le, A. Omelchenko, L. V. Hryshko, and J. Lytton The Molecular Determinants of Ionic Regulatory Differences between Brain and Kidney Na+/Ca2+ Exchanger (NCX1) Isoforms J. Biol. Chem., September 6, 2002; 277(37): 33957 - 33962. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Shigekawa and T. Iwamoto Cardiac Na+-Ca2+ Exchange : Molecular and Pharmacological Aspects Circ. Res., May 11, 2001; 88(9): 864 - 876. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Ruknudin, S. He, W J Lederer, and D. H Schulze Functional differences between cardiac and renal isoforms of the rat Na+-Ca2+ exchanger NCX1 expressed in Xenopus oocytes J. Physiol., December 15, 2000; 529(3): 599 - 610. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Fujioka, K. Hiroe, and S. Matsuoka Regulation kinetics of Na+-Ca2+ exchange current in guinea-pig ventricular myocytes J. Physiol., December 15, 2000; 529(3): 611 - 623. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Poon, S. Leach, X.-F. Li, J. E. Tucker, P. P. M. Schnetkamp, and J. Lytton Alternatively spliced isoforms of the rat eye sodium/calcium+potassium exchanger NCKX1 Am J Physiol Cell Physiol, April 1, 2000; 278(4): C651 - C660. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Kraev, B. D. Quednau, S. Leach, X.-F. Li, H. Dong, R. Winkfein, M. Perizzolo, X. Cai, R. Yang, K. D. Philipson, et al. Molecular Cloning of a Third Member of the Potassium-dependent Sodium-Calcium Exchanger Gene Family, NCKX3 J. Biol. Chem., June 15, 2001; 276(25): 23161 - 23172. [Abstract] [Full Text] [PDF]
|
|
|
|
