Dataset Information

Subunit isoform selectivity in assembly of Na,K-ATPase ?-? heterodimers.

ABSTRACT: To catalyze ion transport, the Na,K-ATPase must contain one ? and one ? subunit. When expressed by transfection in various expression systems, each of the four ? subunit isoforms can assemble with each of the three ? subunit isoforms and form an active enzyme, suggesting the absence of selective ?-? isoform assembly. However, it is unknown whether in vivo conditions the ?-? assembly is random or isoform-specific. The ?(2)-?(2) complex was selectively immunoprecipitated by both anti-?(2) and anti-?(2) antibodies from extracts of mouse brain, which contains cells co-expressing multiple Na,K-ATPase isoforms. Neither ?(1)-?(2) nor ?(2)-?(1) complexes were detected in the immunoprecipitates. Furthermore, in MDCK cells co-expressing ?(1), ?(1), and ?(2) isoforms, a greater fraction of the ?(2) subunits was unassembled with ?(1) as compared with that of the ?(1) subunits, indicating preferential association of the ?(1) isoform with the ?(1) isoform. In addition, the ?(1)-?(2) complex was less resistant to various detergents than the ?(1)-?(1) complex isolated from MDCK cells or the ?(2)-?(2) complex isolated from mouse brain. Therefore, the diversity of the ?-? Na,K-ATPase heterodimers in vivo is determined not only by cell-specific co-expression of particular isoforms, but also by selective association of the ? and ? subunit isoforms.

SUBMITTER: Tokhtaeva E

PROVIDER: S-EPMC3406695 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature

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Subunit isoform selectivity in assembly of Na,K-ATPase α-β heterodimers.

Tokhtaeva Elmira E Clifford Rebecca J RJ Kaplan Jack H JH Sachs George G Vagin Olga O

The Journal of biological chemistry 20120613 31

To catalyze ion transport, the Na,K-ATPase must contain one α and one β subunit. When expressed by transfection in various expression systems, each of the four α subunit isoforms can assemble with each of the three β subunit isoforms and form an active enzyme, suggesting the absence of selective α-β isoform assembly. However, it is unknown whether in vivo conditions the α-β assembly is random or isoform-specific. The α(2)-β(2) complex was selectively immunoprecipitated by both anti-α(2) and anti ...[more]

PMID: 22696220

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Project description:Due to the critical role of cochlear ion channels for hearing, the focus of the present study was to examine age-related changes of Na, K-ATPase (NKA) subunits in the lateral wall of mouse cochlea. We combined qRT-PCR, western blot and immunocytochemistry methodologies in order to determine gene and protein expression levels in the lateral wall of young and aged CBA/CaJ mice. Of the seven NKA subunits, only the mRNA expressions of α1, β1 and β2 subunit isoforms were detected in the lateral wall of CBA/CaJ mice. Aging was accompanied by dys-regulation of gene and protein expression of all three subunits detected. Hematoxylin and eosin (H&E) staining revealed atrophy of the cochlear stria vascularis (SV). The SV atrophy rate (20%) was much less than the ∼80% decline in expression of all three NKA isoforms, indicating lateral wall atrophy and NKA dys-regulation are independent factors and that there is a combination of changes involving the morphology of SV and NKA expression in the aging cochlea which may concomitantly affect cochlear function. Immunoprecipitation assays showed that the α1-β1 heterodimer is the selective preferential heterodimer over the α1-β2 heterodimer in cochlea lateral wall. Interestingly, in vitro pathway experiments utilizing cultured mouse cochlear marginal cells from the SV (SV-K1 cells) indicated that decreased mRNA and protein expressions of α1, β1 and β2 subunit isoforms are not associated with reduction of NKA activity following in vitro application of ouabain, but ouabain did disrupt the α1-β1 heterodimer interaction. Lastly, the association between the α1 and β1 subunit isoforms was present in the cochlear lateral wall of young adult mice, but this interaction could not be detected in old mice. Taken together, these data suggest that in the young adult mouse there is a specific, functional selection and assembly of NKA subunit isoforms in the SV lateral wall, which is disrupted and dys-regulated with age. Interventions for this age-linked ion channel disruption may have the potential to help diagnose, prevent, or treat age-related hearing loss.

Dataset Information

Subunit isoform selectivity in assembly of Na,K-ATPase ?-? heterodimers.

Publications

Subunit isoform selectivity in assembly of Na,K-ATPase α-β heterodimers.

Similar Datasets

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