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Role of cyclin dependent kinase 5 (CDK5) and c‐Abl in high NaCl‐induced nuclear localization of the osmoprotective transcription factor, TonEBP/OREBP
Author(s) -
Gallazzini Morgan,
Kunin Margarita,
Burg Maurice B.,
Ferraris Joan D.
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.933.6
Subject(s) - phosphorylation , cyclin dependent kinase 1 , kinase , transcription factor , nuclear localization sequence , chemistry , cyclin dependent kinase 5 , microbiology and biotechnology , alanine , transcription (linguistics) , biology , biochemistry , protein kinase a , cytoplasm , amino acid , gene , cell cycle , cyclin dependent kinase 2 , linguistics , philosophy
High NaCl activates TonEBP, resulting in increased transcription of protective genes. Early events include phosphorylation of TonEBP and increase in its nuclear to cytoplasmic (n:c) ratio. The purpose of the present studies was to identify specific amino acids that become phosphorylated in TonEBP and to determine whether they have a role in its nuclear localization. By mass spectrometry we previously identified T135 and Y143 as being phosphorylated in TonEBP. Use of phospho‐specific antibodies confirms phosphorylation at those sites and shows that high NaCl increases it. These amino acids are located in the Auxiliary Export Domain (AED) of TonEBP, which is necessary for its export from the nucleus when NaCl is low. MotifScan identifies T135 as a likely site for phosphorylation by CDK5 and Y143 as a likely c‐Abl site. The CDK5 inhibitors roscovitin and CDK1/5 reduce TonEBP n:c ratio, consistent with the hypothesis that CDK5 contributes to localization of TonEBP by phosphorylating T135. Dominant negative c‐Abl decreases TonEBP n:c ratio in cells exposed to high NaCl, as does prevention of phosphorylation of Y143 by mutating it to alanine. Effects on TonEBP n:c ratio of dominant negative c‐Abl and of mutation of Y143 to alanine are equivalent and non‐additive. We conclude that high NaCl stimulates nuclear localization of TonEBP by phosphorylation on T135 and Y143, most likely catalyzed by CDK5 and c‐Abl, respectively.