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Central role of Akt in regulating Clk/Sty, serine/arginine‐rich (SR) protein phosphorylation and alternative splicing
Author(s) -
Cooper Denise R.,
Corbin Karen D.,
Watson James E.,
Hagiwara Masatoshi,
Patel Niketa A.,
Jiang Kun
Publication year - 2006
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.20.4.a539-c
Subject(s) - akt2 , sr protein , phosphorylation , protein kinase b , alternative splicing , akt1 , microbiology and biotechnology , rna splicing , biology , chemistry , biochemistry , exon , gene , rna
SR proteins play essential roles in constitutive and regulated splicing of pre‐mRNAs. Phosphorylation of arginine/serine‐rich (RS) domains by SR protein kinases such as Cdc2‐like kinases (Clk) modulates their subcellular localization and activation. However, it remains unclear how these kinases and their target SR proteins are regulated by extracellular signals. Our prior work suggests that phosphatidylinositol‐3 kinase (PI3K) regulates insulin‐induced protein kinase CβII (PKCβII) alternative splicing. Here we report that insulin regulates pre‐mRNA splicing via Akt‐mediated phosphorylation of Clk1 and SR proteins, since Akt2 and Clk1 enhanced insulin‐induced SR protein phosphorylation. Akt2‐siRNA or PI3K inhibitor suppressed Clk1 and SR protein phosphorylation, indicating that Clk1 mediates Akt2 control of SR proteins. Clk1 inhibitor, TG003, suppressed phosphorylation of SRp75, SRp55 and SRp40 in the presence of activated Akt2. PI3K/Akt‐dependent alternative splicing was suppressed by inhibiting Clk1, demonstrated by Clk1 siRNA blockade of PKCβII exon inclusion. Moreover, SR protein phosphorylation on Akt‐substrate motifs was distinctive from their phosphorylation by Clk1. Further, Akt2‐deficient mice demonstrated impaired Clk1 and SR protein phosphorylation, and decreased PKCβII protein levels. These results established PI3K/Akt as a central event controlling Clk1 and SR proteins in alternative splicing and gene expression. (NIDDK54393 and Dept. Veterans Affairs)