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CHIF, a member of the FXYD protein family, is a regulator of Na,K‐ATPase distinct from the γ‐subunit
Author(s) -
Béguin Pascal,
Crambert Gilles,
Guennoun Saida,
Garty Haim,
Horisberger JeanDaniel,
Geering Käthi
Publication year - 2001
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/20.15.3993
Subject(s) - biology , protein subunit , xenopus , gamma subunit , microbiology and biotechnology , cytoplasm , regulator , homeostasis , membrane protein , biophysics , biochemistry , membrane , gene
The biological role of small membrane proteins of the new FXYD family is largely unknown. The best characterized FXYD protein is the γ‐subunit of the Na,K‐ATPase (NKA) that modulates the Na,K‐pump function in the kidney. Here, we report that, similarly to γa and γb 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 γa and γb, 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 γ‐subunit and CHIF interaction with NKA, while cytoplasmic, positively charged residues are necessary for the γ‐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.