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Acute regulation of the epithelial Na + channel (ENaC) by phosphatidylinositol 3‐kinase in isolated collecting duct principal cells
Author(s) -
Staruschenko Alexander,
Pochynyuk Oleh,
Bugaj Vladislav,
Vandewalle Alain,
Stockand James D
Publication year - 2007
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.21.6.a954
Subject(s) - epithelial sodium channel , wortmannin , ly294002 , reabsorption , chemistry , pten , renal sodium reabsorption , phosphatidylinositol , gating , patch clamp , medicine , endocrinology , microbiology and biotechnology , biophysics , kinase , electrophysiology , pi3k/akt/mtor pathway , signal transduction , biology , sodium , biochemistry , organic chemistry
ENaC activity is rate limiting for Na + reabsorption across the distal nephron. ENaC is a target for PI3‐K and its down‐stream phospholipid‐dependent kinase effectors, including Sgk. Emerging evidence suggests that there is close coupling between PI3‐K and ENaC with the kinase also influencing channel gating independent of Sgk. To further study acute regulation of ENaC by PI3‐K, we isolated cortical collecting ducts (CCD) from rats maintained on a low sodium diet and used patch‐clamp electrophysiology to assess the single channel properties of ENaC. Inhibition of PI3‐K with either wortmannin or LY294002, but not the inactive analogue LY303511, rapidly decreased ENaC open probability and activity. These compounds elicited an identical response in the cortical collecting duct cell line, MPK CCD14 . IGF‐I increased Na + reabsorption across MPK CCD14 cells via PI3‐K with LY294002 completely abolishing IGF‐I actions on transport. In contrast, MAPK and ROCK inhibitors PD98059 and H1152, respectively, had no effect on IGF‐I induced Na + transport. However, the PTEN inhibitor bpV (pic) lessened inhibition of Na + transport by LY294002 stressing the importance of the equilibrium between production and degradation of PIP 3 . These results are the first to demonstrate in a native preparation that PI3‐K acutely influences ENaC gating likely through a mechanism independent of Sgk. Supported by NIH, AHA and NKF.