FXYD-11 associates with Na+-K+-ATPase in the gill of Atlantic salmon: regulation and localization in relation to changed ion-regulatory status

Am J Physiol Regul Integr Comp Physiol. 2010 Nov;299(5):R1212-23. doi: 10.1152/ajpregu.00015.2010. Epub 2010 Aug 11.

Abstract

The Na(+)-K(+)-ATPase is the primary electrogenic component driving transepithelial ion transport in the teleost gill; thus regulation of its level of activity is of critical importance for osmotic homeostasis. In the present study, we examined the dynamics of the gill-specific FXYD-11 protein, a putative regulatory subunit of the pump, in Atlantic salmon during seawater (SW) acclimation, smoltification, and treatment with cortisol, growth hormone, and prolactin. Dual-labeling immunohistochemistry showed that branchial FXYD-11 is localized in Na(+)-K(+)-ATPase immunoreactive cells, and coimmunoprecipitation experiments confirmed a direct association between FXYD-11 and the Na(+)-K(+)-ATPase α-subunit. Transfer of freshwater (FW)-acclimated salmon to SW induced a parallel increase in total α-subunit and FXYD-11 protein expression. A similar concurrent increase was seen during smoltification in FW. In FW fish, cortisol induced an increase in both α-subunit and FXYD-11 abundance, and growth hormone further stimulated FXYD-11 levels. In SW fish, prolactin induced a decrease in FXYD-11 and α-subunit protein levels. In vitro cortisol (18 h, 10 μg/ml) stimulated FXYD-11, but not FXYD-9, mRNA levels in gills from FW and SW salmon. The data show that Na(+)-K(+)-ATPase expressed in branchial mitochondrion-rich cells is accompanied by FXYD-11, and that regulation of the two proteins is highly coordinated. The demonstrated association of FXYD-11 and α-subunit strengthens our hypothesis that FXYD-11 has a role in modulating the pump's kinetic properties. The presence of putative phosphorylation sites on the intracellular domain of FXYD-11 suggests the possibility that this protein also may transmit external signals that regulate Na(+)-K(+)-ATPase activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acclimatization
  • Animals
  • Blotting, Western
  • Fish Proteins / genetics
  • Fish Proteins / metabolism*
  • Gills / drug effects
  • Gills / enzymology*
  • Growth Hormone / metabolism
  • Homeostasis
  • Hydrocortisone / pharmacology
  • Immunohistochemistry
  • Immunoprecipitation
  • Ion Transport
  • Kinetics
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Prolactin / metabolism
  • Protein Subunits
  • RNA, Messenger / metabolism
  • Salinity
  • Salmo salar / genetics
  • Salmo salar / metabolism*
  • Seawater
  • Sodium-Potassium-Exchanging ATPase / genetics
  • Sodium-Potassium-Exchanging ATPase / metabolism*

Substances

  • Fish Proteins
  • Membrane Proteins
  • Protein Subunits
  • RNA, Messenger
  • Prolactin
  • Growth Hormone
  • Sodium-Potassium-Exchanging ATPase
  • Hydrocortisone