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First published online April 8, 2004
Journal of Experimental Biology 207, 1749-1756 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00953
Expression and polarity reversal of V-type H+-ATPase during the mineralizationdemineralization cycle in Porcellio scaber sternal epithelial cells
1 Central Facility for Electron Microscopy, University of Ulm,
Albert-Einstein-Allee 11, 89069 Ulm, Germany
2 University of Osnabrück, Department of Animal Physiology,
Barbarastraße 11, 49076 Osnabrück, Germany
3 Mount Desert Island Biological Laboratory, Salsbury Cove ME 04672,
USA
* Author for correspondence (e-mail: andreas.ziegler{at}medizin.uni-ulm.de)
Accepted 18 February 2004
The formation and resorption of CaCO3 by epithelial cell layers require epithelial transport of protons. We used the anterior sternal epithelium of the terrestrial isopod Porcellio scaber as a model to study the expression pattern and immunolocalization of a V-type H+-ATPase during the mineralization and demineralization of intermittent CaCO3 deposits. Semiquantitative RT-PCR revealed that the expression of the V-type H+-ATPase increases from non Ca2+-transporting control stages to the stages of CaCO3 deposit formation and resorption. In the Ca2+-transporting stages the expression was larger in the anterior than in the posterior sternal epithelium, which is not involved in deposit formation and transports just moderate amounts of CaCO3. Immunocytochemistry of the B-subunit of the V-type H+-ATPase in the anterior sternal epithelium reveals an increase in the abundance of the protein within the basolateral membrane, from undetectable to strong signals in the control stage to the stages of CaCO3 deposit formation, respectively. From the stage of CaCO3 deposit formation to that of CaCO3 resorption the signal decreased within the basolateral plasma membrane and increased within the apical plasma membrane. For the first time the results indicate a contribution of a V-type H+-ATPase to CaCO3 deposition and a reversal of its polarity from the basolateral to the apical plasma membrane compartment within the same cells.
Key words: biomineralization, calcium carbonate, Crustacea, epithelial H+ transport, epithelium, Isopoda, Porcellio scaber
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