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Flexible selection of diversified Na(+)/K(+)-ATPase ?-subunit isoforms for osmoregulation in teleosts.

ABSTRACT: BACKGROUND AND METHODS:Multiple Na+/K+-ATPase (NKA) ?-subunit isoforms express differentially in response to salinity transfer in teleosts but we observed that the isoform nomenclature is inconsistent with the phylogenetic relationship of NKA ?-genes. We cloned the catalytic NKA ?-subunit isoforms in eels and medaka, analyzed the time course of their expressions in osmoregulatory tissues after transfer from freshwater (FW) to seawater (SW), and performed phylogenetic analyses to deduce an evolutionary scenario that illustrates how various duplication events have led to the current genomic arrangement of NKA ?-genes in teleosts. RESULTS AND DISCUSSION:Five and six ?-subunits were cloned in eels and medaka respectively. In eels, the commonly-reported ?1a and ?1b isoforms were absent while the ?1c isoform was diversified instead (?1c-1, ?1c-2, ?1c-3, ?2, and ?3 in eels). Phylogenetic estimation indicated that the ?1a and ?1b isoforms from salmon, tilapia, and medaka were generated by independent duplication events and thus they are paralogous isoforms. Re-examination of expression changes of known isoforms after salinity challenge revealed that the isoforms selected as predominant SW-types varied among teleost lineages. Diversification of ?1 isoforms occurred by various types of gene duplication, or by alternative transcription among tandem genes to form chimeric transcripts, but there is no trend for more ?1 copies in euryhaline species. Our data suggest that the isoform switching between FW (?1a predominates) and SW (?1b predominates) that occurs in salmonids is not universal in teleosts. Instead, in eels, ?1c-1 was the major ?-subunit upregulated gill, intestine, and kidney in SW. Localization of both NKA mRNA and protein showed consistent upregulation in gill and intestine in SW eels, but not in renal distal and collecting tubules, where low transcript expression levels were accompanied by high protein levels, suggesting a tissue-specific translational regulation that determines and fine-tunes the NKA expression. In medaka, ?1b was upregulated in SW in anterior intestine while most other ?-subunit isoforms were less responsive to salinity changes. CONCLUSION:By integrating gene expression and phylogenetic results, we propose that the major NKA ?-subunits for SW acclimation were not ancestrally selected, but rather were flexibly determined in lineage-specific fashion in teleosts.

SUBMITTER: Wong MK

PROVIDER: S-EPMC4971688 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Flexible selection of diversified Na(+)/K(+)-ATPase α-subunit isoforms for osmoregulation in teleosts.

Wong Marty Kwok-Shing MK Pipil Supriya S Ozaki Haruka H Suzuki Yutaka Y Iwasaki Wataru W Takei Yoshio Y

Zoological letters 20160803

<h4>Background and methods</h4>Multiple Na+/K+-ATPase (NKA) α-subunit isoforms express differentially in response to salinity transfer in teleosts but we observed that the isoform nomenclature is inconsistent with the phylogenetic relationship of NKA α-genes. We cloned the catalytic NKA α-subunit isoforms in eels and medaka, analyzed the time course of their expressions in osmoregulatory tissues after transfer from freshwater (FW) to seawater (SW), and performed phylogenetic analyses to deduce a ...[more]

PMID: 27489726

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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

Flexible selection of diversified Na(+)/K(+)-ATPase ?-subunit isoforms for osmoregulation in teleosts.

Publications

Flexible selection of diversified Na(+)/K(+)-ATPase α-subunit isoforms for osmoregulation in teleosts.

Similar Datasets

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