RGD Reference Report - Beta-subunit of cardiac Na+-K+-ATPase dictates the concentration of the functional enzyme in caveolae. - Rat Genome Database

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Beta-subunit of cardiac Na+-K+-ATPase dictates the concentration of the functional enzyme in caveolae.

Authors: Liu, L  Askari, A 
Citation: Liu L and Askari A, Am J Physiol Cell Physiol. 2006 Oct;291(4):C569-78. Epub 2006 Apr 19.
RGD ID: 2302992
Pubmed: PMID:16624992   (View Abstract at PubMed)
DOI: DOI:10.1152/ajpcell.00002.2006   (Journal Full-text)

Previous studies showed the presence of a significant fraction of Na(+)-K(+)-ATPase alpha-subunits in cardiac myocyte caveolae, suggesting the caveolar interactions of Na(+)-K(+)-ATPase with its signaling partners. Because both alpha- and beta-subunits are required for ATPase activity, to clarify the status of the pumping function of caveolar Na(+)-K(+)-ATPase, we have examined the relative distribution of two major subunit isoforms (alpha(1) and beta(1)) in caveolar and noncaveolar membranes of adult rat cardiac myocytes. When cell lysates treated with high salt (Na(2)CO(3) or KCl) concentrations were fractionated by a standard density gradient procedure, the resulting light caveolar membranes contained 30-40% of alpha(1)-subunits and 80-90% of beta(1)-subunits. Use of Na(2)CO(3) was shown to inactivate Na(+)-K(+)-ATPase; however, caveolar membranes obtained by the KCl procedure were not denatured and contained approximately 75% of total myocyte Na(+)-K(+)-ATPase activity. Sealed isolated caveolae exhibited active Na(+) transport. Confocal microscopy supported the presence of alpha,beta-subunits in caveolae, and immunoprecipitation showed the association of the subunits with caveolin oligomers. The findings indicate that cardiac caveolar inpocketings are the primary portals for active Na(+)-K(+) fluxes, and the sites where the pumping and signaling functions of Na(+)-K(+)-ATPase are integrated. Preferential concentration of beta(1)-subunit in caveolae was cell specific; it was also noted in neonatal cardiac myocytes but not in fibroblasts and A7r5 cells. Uneven distributions of alpha(1) and beta(1) in early and late endosomes of myocytes suggested different internalization routes of two subunits as a source of selective localization of active Na(+)-K(+)-ATPase in cardiac caveolae.

Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
potassium ion transport  IDA 2302992; 2302992; 2302992; 2302992 RGD 
sodium ion transport  IDA 2302992; 2302992; 2302992; 2302992 RGD 

Cellular Component
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
caveola  IDA 2302992; 2302992; 2302992; 2302992; 2302992; 2302992 RGD 
sodium:potassium-exchanging ATPase complex  IDA 2302992; 2302992; 2302992; 2302992 RGD 

Molecular Function
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
P-type sodium:potassium-exchanging transporter activity  IDA 2302992; 2302992; 2302992; 2302992 RGD 

Objects Annotated

Genes (Rattus norvegicus)
Atp1a1  (ATPase Na+/K+ transporting subunit alpha 1)
Atp1a2  (ATPase Na+/K+ transporting subunit alpha 2)
Atp1b1  (ATPase Na+/K+ transporting subunit beta 1)
Atp1b3  (ATPase Na+/K+ transporting subunit beta 3)
Cav2  (caveolin 2)
Cav3  (caveolin 3)


Additional Information