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Semin Nephrol. 1999 Sep;19(5):421-30.

Nongastric H+,K+-ATPase: cell biologic and functional properties.

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1
Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06510, USA.

Abstract

Several members of the H+,K+-ATPase family of ion pumps participate in renal K transport. This class of P-type ATPases includes the gastric H+,K+-ATPase as well as a number of nongastric H+,K+-ATPase isoforms. Physiological studies suggest that these enzymes operate predominantly at the apical surfaces of tubule epithelial cells. Although much has been learned about the pattern of H+,K+-ATPase isoform expression and its response to stress, the functional and cell biologic attributes of these pumps remain largely unelucidated. We have studied the properties of renal H+,K+-ATPases both in vitro and in situ. Our analysis of ion fluxes driven by a nongastric H+,K+-ATPase isoform suggests that it exchanges Na (rather than H) for K under normal circumstances. Thus, the individual H+,K+-ATPase isoforms may make diverse contributions to renal cation transport. We find that the activities of renal H+,K+-ATPases in situ are regulated by endocytosis, which is mediated by an endocytosis signal in the cytoplasmic tail of the gastric H+,K+-ATPase beta-subunit. Transgenic mice expressing a version of this protein in which the signal has been disabled show constitutively active renal K resorption. The identities of the H+,K+-ATPase isoforms that are normally subject to endocytic regulation and the nature of the participating epithelial cell machinery have yet to be established.

PMID:
10511382
[Indexed for MEDLINE]
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