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Increased UT‐A1 ubiquitination is partially due to decreased deubiquitination activity in Streptozotocin‐induced diabetic rat kidney inner medulla
Author(s) -
Su Hua,
Ilori Titilayo O,
Klein Janet D,
Sands Jeff M,
Chen Guangping
Publication year - 2013
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.27.1_supplement.1111.4
Subject(s) - ubiquitin , chemistry , gene knockdown , streptozotocin , in vitro , microbiology and biotechnology , endocrinology , apoptosis , biochemistry , biology , diabetes mellitus , gene
The urea transporter UT‐A1 protein abundance in kidney inner medulla (IM) is dramatically increased under diabetic conditions to compensate for the osmotic diuresis caused by glucosuria. In this study, we examined UT‐A1 ubiquitination and degradation in a streptozotocin‐induced diabetic animal model. IM tissue lysates were immunoprecipitated with UT‐A1 antibody followed by immunoblotting with ubiquitin antibody. The smeared large size bands indicating ubiquitinated UT‐A1 were significantly increased. We further found that the de‐ubiquitination enzymes, ubiquitin‐specific proteases 18 (USP18) and USP24, were downregulated in diabetic rat IM. In vitro deubiquitination assays were performed and revealed a decrease in deubiquitination activity from diabetic rat IM lysates. We then specifically examined the effect of USP24 on UT‐A1 deubiquitination. USP24 directly interacted with UT‐A1 and promoted UT‐A1 deubiquitination in vitro. Knockdown of USP24 in UT‐A1 HEK293 cells increased both cell surface and total UT‐A1 degradation. By using sucrose gradient ultracentrifugation, we found that USP24 was absent in the cell plasma membrane and mainly present in early endosomes where it is co‐distributed with Rab5. Our study demonstrates that deubiquitination enzymes, like USP24, may play an important role in regulating UT‐A1 expression by affecting protein ubiquitination and degradation