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XB-ART-8629
EMBO J 2001 Aug 01;2015:3993-4002. doi: 10.1093/emboj/20.15.3993.
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CHIF, a member of the FXYD protein family, is a regulator of Na,K-ATPase distinct from the gamma-subunit.

Béguin P, Crambert G, Guennoun S, Garty H, Horisberger JD, Geering K.


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The biological role of small membrane proteins of the new FXYD family is largely unknown. The best characterized FXYD protein is the gamma-subunit of the Na,K-ATPase (NKA) that modulates the Na,K-pump function in the kidney. Here, we report that, similarly to gamma(a) and gamma(b) splice variants, the FXYD protein CHIF (corticosteroid-induced factor) is a type I membrane protein which is associated with NKA in renal tissue, and modulates the Na,K-pump transport when expressed in Xenopus oocytes. In contrast to gamma(a) and gamma(b), which both decrease the apparent Na+ affinity of the Na,K-pump, CHIF significantly increases the Na+ affinity and decreases the apparent K+ affinity due to an increased Na+ competition at external binding sites. The extracytoplasmic FXYD motif is required for stable gamma-subunit and CHIF interaction with NKA, while cytoplasmic, positively charged residues are necessary for the gamma-subunit's association efficiency and for CHIF's functional effects. These data document that CHIF is a new tissue-specific regulator of NKA which probably plays a crucial role in aldosterone-responsive tissues responsible for the maintenance of body Na+ and K+ homeostasis.

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Species referenced: Xenopus laevis
Genes referenced: atp1a1

References [+] :
Arystarkhova, The gamma subunit modulates Na(+) and K(+) affinity of the renal Na,K-ATPase. 1999, Pubmed