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POSH decreases ROMK1 channel activity through stimulating clatharin‐independent and dynamin‐dependent endocytosis.
Author(s) -
Lin Daohong,
Yue Peng,
Sun Peng,
Jin Yan,
Roos Marcel,
Caplan Michael,
Wang Wenhui
Publication year - 2008
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.22.1_supplement.1180.1
Subject(s) - dynamin , chemistry , endocytosis , internalization , microbiology and biotechnology , inhibitory postsynaptic potential , potassium channel , biology , biophysics , endocrinology , biochemistry , receptor
Through a yeast‐two‐hybrid‐screen we detected an interaction between POSH and the C‐terminus of ROMK1. Immunostaining reveals that POSH is highly expressed in the renal cortical collecting duct (CCD). Moreover, immunoprecipitation of renal tissue lysate with ROMK antibody can pull‐down POSH. To study the effect of POSH expression on ROMK1 channels, we used two‐electrode voltage clamp to measure the K current in oocytes injected with ROMK1 or ROMK1+POSH. Co‐injection of 1, 2.5, 5 and 10 ng POSH RNA decreased K current in oocytes injected with 5 ng ROMK1 RNA by 12%, 25%, 45% and 50%, respectively. The effect of POSH on ROMK1 channels was specific because POSH did not inhibit Na current in oocytes injected with ENaC‐alpha, beta and gamma subunits. The inhibitory effect of POSH on ROMK1 channels requires the RING domain of POSH since deleting the RING domain abolished the inhibitory effect of POSH on ROMK1 channels. Also, the inhibitory effect of POSH on ROMK channels was absent in oocytes injected with dominant negative dynamin. However, POSH still decreased the K current in oocytes injected with a ROMK1 mutant in which amino acid residues 373–378 that contain the clathrin‐dependent tyrosine‐based internalization signal were deleted. We conclude that POSH‐induced inhibition of ROMK channels is due to stimulation of the dynamin‐dependent and clathring‐independent endocytosis.