Na + K + ATPase isoform switching in zebrafish during transition to dilute freshwater habitats

Na K ATPase (NKA) is crucial to branchial ion transport as it uses the energy from ATP to move Na against its electrochemical gradient. When fish encounter extremely dilute environments the energy available from ATP hydrolysis may not be sufficient to overcome thermodynamic constraints on ion transp...

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Bibliographic Details
Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2019-05, Vol.286 (1903), p.20190630-20190630
Main Authors: Esbaugh, Andrew J, Brix, Kevin V, Grosell, Martin
Format: Article
Language:English
Subjects:
Acclimatization - physiology
Animals
Development and Physiology
Fresh Water
Isoenzymes - genetics
Isoenzymes - metabolism
Sodium-Potassium-Exchanging ATPase - genetics
Sodium-Potassium-Exchanging ATPase - metabolism
Zebrafish - genetics
Zebrafish - metabolism
Zebrafish Proteins - genetics
Zebrafish Proteins - metabolism
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Summary:Na K ATPase (NKA) is crucial to branchial ion transport as it uses the energy from ATP to move Na against its electrochemical gradient. When fish encounter extremely dilute environments the energy available from ATP hydrolysis may not be sufficient to overcome thermodynamic constraints on ion transport. Yet many fish species-including zebrafish-are capable of surviving in dilute environments. Despite much study, the physiological mechanisms by which this occurs remain poorly understood. Here, we demonstrate that zebrafish acclimated to less than 10 µM Na water exhibit upregulation of a specific NKA α subunit ( zatp1a1a.5) that, unlike most NKA heterotrimers, would result in transfer of only a single Na and K per ATP hydrolysis reaction. Thermodynamic models demonstrate that this change is sufficient to reduce the activation energy of NKA, allowing it to overcome the adverse electrochemical gradient imposed by dilute freshwater. Importantly, upregulation of zatp1a1a.5 also coincides with the recovery of whole body Na post-transfer, which occurs within 24 h. While these structural modifications are crucial for allowing zebrafish to survive in ion-poor environments, phylogenetic and structural analysis of available α subunits from a range of teleosts suggests this adaptation is not widely distributed.
ISSN:0962-8452
1471-2954
DOI:10.1098/rspb.2019.0630