![]()
|
|
||||||||
J. Biol. Chem., Vol. 281, Issue 13, 8332-8338, March 31, 2006
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1



2
From the
Laboratorium voor Fysiologie, K. U. Leuven Campus Gasthuisberg, O/N Herestraat 49/802, B-3000 Leuven, Belgium, ¶Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, United Kingdom, and
Department of Basic Medical Sciences, St. George's University of London, Cranmer Terrace, London SW17 0RE, United Kingdom
Calmodulin (CaM) is a ubiquitous Ca2+ sensor protein that plays an important role in regulating a large number of Ca2+ channels, including the inositol 1,4,5-trisphosphate receptor (IP3R). Despite many efforts, the exact mechanism by which CaM regulates the IP3R still remains elusive. Here we show, using unidirectional 45Ca2+ flux experiments on permeabilized L15 fibroblasts and COS-1 cells, that endogenously bound CaM is essential for the proper activation of the IP3R. Removing endogenously bound CaM by titration with a high affinity (pM) CaM-binding peptide derived from smooth muscle myosin light-chain kinase (MLCK peptide) strongly inhibited IP3-induced Ca2+ release. This inhibition was concentration- and time-dependent. Removing endogenously bound CaM affected the maximum release capacity but not its sensitivity to IP3. A mutant peptide with a strongly reduced affinity for CaM did not affect inhibited IP3-induced Ca2+ release. Furthermore, the inhibition by the MLCK peptide was fully reversible. Re-adding exogenous CaM, but not CaM1234, reactivated the IP3R. These data suggest that, by using a specific CaM-binding peptide, we removed endogenously bound CaM from a high affinity CaM-binding site on the IP3R, and this resulted in a complete loss of the IP3R activity. Our data support a new model whereby CaM is constitutively associated with the IP3R and functions as an essential subunit for proper functioning of the IP3R.
Received for publication, October 17, 2005 , and in revised form, December 19, 2005.
* This work was supported by Grants G.0210.03 (to H. D. S. and J. B. P.) G.O0382.05 (to L. M. and G. C.) of the Fund for Scientific Research Flanders (Belgium), by Grant GOA2004/07 from the Concerted Actions of the K. U. Leuven Institute (to L. M., H. D. S., G. C., and J. B. P.) and by the Interuniversity Poles of Attraction Programme Belgian State, Prime Minister's Office, Federal Office for Scientific, Technical and Cultural Affairs, IUAP P5/05. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1 A postdoctoral fellow of the Research Foundation (FWO-Vlaanderen) Brussels, Belgium.
2 To whom correspondence should be addressed: Laboratorium voor Fysiologie, K. U. Leuven Campus Gasthuisberg, Herestraat 49/802, B-3000 Leuven, Belgium. Tel.: 32-16-34-57-25; Fax: 32-16-34-59-91; E-mail: humbert.desmedt{at}med.kuleuven.be.
![]()
CiteULike
Complore
Connotea
Del.icio.us
Digg
Reddit
Technorati What's this?
This article has been cited by other articles:
![]() |
G. G. Rodney Calmodulin in adult mammalian skeletal muscle: localization and effect on sarcoplasmic reticulum Ca2+ release Am J Physiol Cell Physiol, May 1, 2008; 294(5): C1288 - C1297. [Abstract] [Full Text] [PDF] |
||||
![]() |
Z. Zhou, J. Yin, Z. Dou, J. Tang, C. Zhang, and Y. Cao The Calponin Homology Domain of Vav1 Associates with Calmodulin and Is Prerequisite to T Cell Antigen Receptor-induced Calcium Release in Jurkat T Lymphocytes J. Biol. Chem., August 10, 2007; 282(32): 23737 - 23744. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. K. Foskett, C. White, K.-H. Cheung, and D.-O. D. Mak Inositol Trisphosphate Receptor Ca2+ Release Channels Physiol Rev, April 1, 2007; 87(2): 593 - 658. [Abstract] [Full Text] [PDF] |
||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| All ASBMB Journals | Molecular and Cellular Proteomics |
| Journal of Lipid Research | ASBMB Today |