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Characterization of the Na+, K(+)-ATPase in isolated bovine articular chondrocytes; molecular evidence for multiple alpha and beta isoforms.

Mobasheri, A, Errington, RJ, Golding, S, Hall, AC and Urban, JP (1997) Characterization of the Na+, K(+)-ATPase in isolated bovine articular chondrocytes; molecular evidence for multiple alpha and beta isoforms. Cell Biol Int, 21 (4). pp. 201-212.

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We have used isoform-specific antibodies against the Na+, K(+)-ATPase alpha (alpha 1, alpha 2 and alpha 3) and beta (beta 1 and beta 2) subunit isoforms in order to establish their specific localization in isolated bovine articular chondrocytes. Immunoblotting confirmed the presence of the alpha 1 and alpha 3 isoforms, although alpha 1 expression was significantly greater than alpha 3 as assessed by immunofluorescence confocal laser scanning microscopy and PCR. A similar approach revealed the presence of the beta 1 and beta 2 isoforms in chondrocytes, although beta 2 immunostaining on the plasma membrane was more punctate than beta 1 which in contrast predominated in a subcellular compartment. The plasma membrane abundance of the Na+, K(+)-ATPase was found to be sensitive to the extracellular ionic concentration and long-term elevation of extracellular Na+ concentration significantly upregulated Na+, K(+)-ATPase density as measured by specific 3H-ouabain binding. Our observations suggest that the expression of alpha 3 and beta 2 is not restricted to excitable tissues as previously reported. The physiological relevance of alpha 3 expression in chondrocytes may be related to its low affinity for intracellular Na+ in an extracellular environment where Na+ concentration is unusually high (260-350 mM) compared to other cell types (140 mM). Glycoproteins and their branched carbohydrates have been implicated in cell recognition events, thus the beta 2 subunit glycoprotein may allow the chondrocyte to detect changes in its extracellular environment by physically interacting with components of the cellular cytoskeleton and matrix macromolecules.

Item Type: Article
Authors :
Date : April 1997
Identification Number : 10.1006/cbir.1997.0137
Uncontrolled Keywords : Animals, Antibodies, Blotting, Western, Cartilage, Articular, Cattle, Isoenzymes, Polymerase Chain Reaction, Sodium-Potassium-Exchanging ATPase
Related URLs :
Depositing User : Symplectic Elements
Date Deposited : 17 May 2017 10:17
Last Modified : 17 May 2017 14:48

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