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EAST/SeSAME syndrome mutations disrupt function of heteromeric Kir2.3/Kir4.1 channels at the basolateral membrane of the distal nephron
Author(s) -
Ortega Bernardo,
Li Dimin,
Kim BoYoung,
Wade James B,
Welling Paul A
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1041.23
Subject(s) - xenopus , reabsorption , epithelial polarity , apical membrane , chemistry , microbiology and biotechnology , nephron , biology , endocrinology , medicine , kidney , cell , biochemistry , membrane , gene
Basolateral inwardly rectifying K channels (Kir) in the distal nephron are essential for salt and mineral reabsorption. Mutations in Kir 4.1 cause profound renal salt wasting (EAST/SeSAME syndrome), suggesting that Kir 4.1 plays a dominant role through assembly with the other Kir subunits, like Kir 5.1. Here, we report that Kir2.3 and Kir4.1 co‐immunoprecipitate when co‐expressed in Cos cells, and co‐localize in the mouse distal nephron. As studied in Xenopus oocytes, co‐expression of Kir 2.3 with Kir4.1 potentiated K current density and increased cell surface expression. A dominant negative mutation in the Kir4.1 blocked Kir2.3 activity, and a comparable mutation in Kir2.3 inhibited Kir4.1, indicating heteromeric assembly. At the single channel level, Kir2.3/4.1 channels exhibit properties different than Kir2.3 or Kir4.1 alone, more similar to the native channel in the CCD basolateral membrane. Interestingly, of the 6 studied EAST/SeSAME syndrome mutations, 4 of them (C140R, T164I, R297C, R199X) reduced Kir4.1/5.1 function, and 3 of them (R65P, C140R, T164I) exerted a similar effect on Kir2.3. In conclusion: 1) basolateral K channels of the distal nephron can be formed through heteromeric assembly of Kir4.1/5.1 or Kir4.1/2.3 subunits; 2) Consequently, the inhibitory effects of EAST/SeSAME syndrome mutations can be broadly transmitted throughout the basolateral membrane conductance. Funds from NIH & AHA.