title: Studies on a PMCA-like protein in the outer mantle epithelium of Anodonta cygnea: insights on calcium transcellular dynamics.
abstract: Early studies on the outer mantle epithelium (OME) cells of the freshwater bivalve Anodonta cygnea (Linnaeus, 1758) revealed high ionic calcium concentrations by electrophysiological methods and subsequently a high tendency to reach an intracellular toxic condition. This toxicity could be neutralized by specific mechanisms in the cytosol of OME cells of A. cygnea. The present immunocytochemistry studies of OME cells by light and transmission electron microscopy (TEM) clearly showed a positive reaction of an antibody directed against the human plasma membrane Ca(2+)-ATPase 1 (PMCA-1) in the cytoplasm of OME cells. Also, western blot analysis of different fractions of OME cells with anti human PMCA-1 and C28R2 antibodies confirmed the presence of a PMCA-like protein with an unusual topographical localization and a molecular weight of only 70-80 kDa. These results lead us to speculate that this PMCA-like protein is distributed either in the plasma membrane or in the entire cytosol, where it eventually regulates intracellular calcium levels. Interestingly, the antibody reactions showed seasonal variations, being highest in OME samples prepared during summer when A. cygnea live under natural acidosis and absent in samples taken in winter conditions, which is in accordance with the seasonal variation of shell calcification rates. During winter, PMCA-1 antibody reaction was also detected in OME cells of animals kept only under experimentally induced acidosis conditions. Therefore, we assume that a functional role for this PMCA-like protein in the intracellular calcium regulation of OME cells during the mineralization of the shells of A. cygnea can be speculated.
authors: Laboratório de Fisiologia Aplicada, ICBAS, Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Lg. Prof. Abel Salazar, 4099-003, Porto, Portugal.
authors: Manuel
authors: M
authors: Lopes-Lima
authors: Reiner
authors: R
authors: Bleher
authors: Tassilo
authors: T
authors: Forg
authors: Mathias
authors: M
authors: Hafner
authors: Jorge
authors: J
authors: Machado
mesh_terms: D000818:Animals; D049877:Anodonta / Q000201:enzymology* / Q000648:ultrastructure; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004847:Epithelial Cells / Q000201:enzymology* / Q000648:ultrastructure; D007150:Immunohistochemistry; D046529:Microscopy, Electron, Transmission; D008970:Molecular Weight; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000378:metabolism*; D012621:Seasons
chemical_list: D053499:Plasma Membrane Calcium-Transporting ATPases; D002118:Calcium
references: Biochim Biophys Acta. 1964 Jul 29;88:225-7
references: 14205493
references: Comp Biochem Physiol B Biochem Mol Biol. 2000 Mar;125(3):293-306
references: 10818264
references: J Exp Biol. 2004 Aug;207(Pt 17):2991-3002
references: 15277554
references: Plant Physiol. 1999 Apr;119(4):1165-76
references: 10198075
references: Am J Physiol. 1992 Jul;263(1 Pt 2):R76-83
references: 1322068
references: Science. 1960 Mar 11;131(3402):735
references: 14409383
references: Tissue Cell. 1988;20(5):797-807
references: 18620246
references: J Exp Biol. 2002 Jul;205(Pt 13):1935-42
references: 12077170
references: J Exp Zool A Comp Exp Biol. 2004 May 1;301(5):419-27
references: 15114649
references: Anal Biochem. 1992 Aug 15;205(1):22-6
references: 1443557
references: Nephrol Dial Transplant. 2001 Jul;16(7):1329-35
references: 11427620
references: J Gen Physiol. 1968 Apr;51(4):478-96
references: 4967974
references: Comp Biochem Physiol A Mol Integr Physiol. 2002 Jul;132(3):541-53
references: 12044764