Structural Studies of the Ca2+ Regulatory Domain of Drosophila Na+/Ca2+ Exchanger CALX

  • Lei ZhengEmail author
  • Mousheng Wu
  • Shuilong Tong
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 961)


CALX, the NCX homolog in Drosophila, involves in light-mediated Ca2+ homeostasis in sensory neuronal cells. CALX exhibits a unique negative Ca2+ regulatory property mediated by Ca2+ binding at its intracellular regulatory domain. Our structural studies of individual CBD1 or CBD2 domain reveal that CBD1 is the only Ca2+ binding domain in CALX. Crystal structures of the entire Ca2+ regulatory domain CBD12 from two alternative splicing isoforms, CALX1.1 and CALX1.2, demonstrate that CBD1 and CBD2 form an open V-shaped conformation with four Ca2+ ions bound on the CBD domain interface. The structures together with Ca2+ binding analyses strongly argue that the Ca2+ inhibition of CALX is achieved by interdomain conformational change induced by Ca2+ binding at CBD1. The conformational difference between the two isoforms also raises a hypothesis that alternative splicing residues adjust the interdomain orientation angle between CBD1 and CBD2 to modify the Ca2+ regulatory property of the exchanger. These studies not only establish structural basis to understand the inhibitory Ca2+ regulation and the alternative splicing modification of CALX, but also shed light on the general Ca2+ regulatory mechanism of other mammalian NCX proteins.


Drosophila CALX Sodium-calcium exchange 


  1. D.M. Bers, Excitation–Contraction Coupling and Cardiac Contractile Force (Kluwer, Boston, 2001), pp. 71–92CrossRefGoogle Scholar
  2. G.M. Besserer, M. Ottolia, D.A. Nicoll, V. Chaptal, D. Cascio, K.D. Philipson, J. Abramson, The second Ca2+-binding domain of the Na+-Ca2+ exchanger is essential for regulation: crystal structures and mutational analysis. Proc. Natl. Acad. Sci. U. S. A. 104, 18467–18472 (2007)PubMedCrossRefGoogle Scholar
  3. M.P. Blaustein, G. Fontana, R.S. Rogowski, The Na+-Ca2+ exchanger in rat brain synaptosomes. Kinetics and regulation. Ann. N. Y. Acad. Sci. 779, 300–317 (1996)PubMedCrossRefGoogle Scholar
  4. X. Cai, J. Lytton, The Cation/Ca Exchanger Superfamily: Phylogenetic Analysis and Structural Implications. Mol. Biol. Evol. 21, 1692–1703 (2004)PubMedCrossRefGoogle Scholar
  5. C. Dyck, A. Omelchenko, C.L. Elias, B.D. Quednau, K.D. Philipson, M. Hnatowich, L.V. Hryshko, Ionic regulatory properties of brain and kidney splice variants of the NCX1 Na+-Ca2+ exchanger. J. Gen. Physiol. 114, 701–711 (1999)PubMedCrossRefGoogle Scholar
  6. M. Hilge, J. Aelen, G.W. Vuister, Ca2+ regulation in the Na+/Ca2+ exchanger involves two markedly different Ca2+ sensors. Mol. Cell 22, 15–25 (2006)PubMedCrossRefGoogle Scholar
  7. L.V. Hryshko, S. Matsuoka, D.A. Nicoll, J.N. Weiss, E.M. Schwarz, S. Benzer, K.D. Philipson, Anomalous regulation of the Drosophila Na+-Ca2+ exchanger by Ca2+. J. Gen. Physiol. 108, 67–74 (1996)PubMedCrossRefGoogle Scholar
  8. E. Johnson, L. Bruschweiler-Li, S.A. Showalter, G.W. Vuister, F. Zhang, R. Brüschweiler, Structure and dynamics of Ca2+-binding domain 1 of the Na+/Ca2+ exchanger in the presence and in the absence of Ca2+. J. Mol. Biol. 377, 945–955 (2008)PubMedCrossRefGoogle Scholar
  9. S. Matsuoka, D.A. Nicoll, R.F. Reilly, D.W. Hilgemann, K.D. Philipson, Initial localization of regulatory regions of the cardiac sarcolemmal Na+-Ca2+ exchanger. Proc. Natl. Acad. Sci. U. S. A. 90, 3870–3874 (1993)PubMedCrossRefGoogle Scholar
  10. D.A. Nicoll, M.R. Sawaya, S. Kwon, K.D. Cascio, D.A. Philipson, J. Abramson, The crystal structure of the primary Ca2+ sensor of the Na+/Ca2+ exchanger reveals a novel Ca2+ binding motif. J. Biol. Chem. 281, 21577–21581 (2006)PubMedCrossRefGoogle Scholar
  11. A. Omelchenko, C. Dyck, M. Hnatowich, J. Buchko, D.A. Nicoll, K.D. Philipson, L.V. Hryshko, Functional differences in ionic regulation between alternatively spliced isoforms of the Na+-Ca2+ exchanger from Drosophila melanogaster. J. Gen. Physiol. 111, 691–702 (1998)PubMedCrossRefGoogle Scholar
  12. M. Ottolia, K.D. Philipson, S. John, Conformational changes of the Ca2+ regulatory site of the Na+-Ca2+ exchanger detected by FRET. Biophys. J. 87, 899–906 (2004)PubMedCrossRefGoogle Scholar
  13. K.D. Philipson, D.A. Nicoll, Sodium-calcium exchange: a molecular perspective. Annu rev. physiol. 62, 111–133 (2000)PubMedCrossRefGoogle Scholar
  14. R. Ranganathan, G.L. Harris, C.F. Stevens, C.S. Zuker, A Drosophila mutant defective in extracellular calcium-dependent photoreceptor deactivation and desensitization. Nature 354, 230–232 (1991)PubMedCrossRefGoogle Scholar
  15. E.M. Schwarz, S. Benzer, Calx, a Na-Ca exchanger gene of Drosophila melanogaster. Proc. Natl. Acad. Sci. U. S. A. 94, 10249–10254 (1997)PubMedCrossRefGoogle Scholar
  16. T. Wang, C. Montell, Phototransduction and retinal degeneration in Drosophila. Pflugers Arch-Eur. J. Physiol. 454, 821–847 (2007)CrossRefGoogle Scholar
  17. T. Wang, H. Xu, J. Oberwinkler, Y. Gu, R.C. Hardie, C. Montell, Light activation, adaptation, and cell survival functions of the Na+/Ca2+ exchanger CalX. Neuron 45, 367–378 (2005)PubMedCrossRefGoogle Scholar
  18. M. Wu, M. Wang, J. Nix, L.V. Hryshko, L. Zheng, Crystal structure of CBD2 from the Drosophila Na+/Ca2+ exchanger: diversity of Ca2+ regulation and its alternative splicing modification. J. Mol. Biol. 387, 104–112 (2009)PubMedCrossRefGoogle Scholar
  19. M. Wu, H.D. Le, M. Wang, V. Yurkov, A. Omelchenko, M. Hnatowich, J. Nix, L.V. Hryshko, L. Zheng, Crystal structures of progressive Ca2+ binding states of the Ca2+ sensor CBD1 from the CALX Na+/Ca2+ exchanger reveal incremental conformational transitions. J. Biol. Chem. 285, 2554–2561 (2010)PubMedCrossRefGoogle Scholar
  20. M. Wu, S. Tong, J. Gonzalez, V. Jayaraman, J.L. Spudich, L. Zheng, Structural basis of the Ca2+ inhibitory mechanism of Drosophila Na+/Ca2+ exchanger CALX and its modification by alternative splicing. Structure 19, 1509–1517 (2011)PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  1. 1.Center for Membrane Biology, Department of Biochemistry and Molecular BiologyThe University of Texas Houston Medical SchoolHoustonUSA

Personalised recommendations