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PPB is a Novel Serine/Threonine Phosphatase of Akt and is Involved in Myogenesis
Author(s) -
Duan Xueyan,
Tao Shen,
Gao Xinxin,
Zhang Jin,
Lin Xia,
Feng XinHua
Publication year - 2010
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.24.1_supplement.863.2
Subject(s) - protein kinase b , phosphatase , myogenesis , c2c12 , phosphorylation , pi3k/akt/mtor pathway , akt1 , microbiology and biotechnology , kinase , akt2 , biology , chemistry , biochemistry , signal transduction , myocyte
PI3 kinase/Akt signaling pathway plays a central role in many biological functions. There are two phosphorylation sites on Akt (Thr308 and Ser473), which are phosphorylated by PI3‐kinase/PDK1 and mTOR‐rictor kinase complex, respectively. Recently, PH domain and leucine rich repeat protein phosphatase 1(PHLPP1) was identified to dephosphorylate pSer473. The identity of phosphatase on Thr308 is still elusive. We screened for Akt phosphatase on Ser473 and Thr308 in mammalian cells. Of 45 phosphatases, we identified PPB ( P rotein P hosphatase for Akt/PK B ) as a potent phosphatase that dephosphorylates both Thr308 and Ser473. This was supported by both in vivo and in vitro phosphatase assays. Fluorescence resonance energy transfer (FRET) analysis using AktAR reporter indicates that PPB reduces Akt activity in live cells. However, PPB dead mutant doesn't dephosphorylate Akt. All these data suggest that PPB dephosphorylates Akt and reduces its kinase activity. PI3K/Akt pathway plays an important role during myogenesis. To study the effect of PPB on myogenesis, we generated C2C12 stable cells that over‐express PPB. When C2C12 control and stable cells were differentiated for up to 3 days, the expression of two important myogenetic markers, myosin heavy chain (MHC) and myogenin was abolished, However, this can be rescued with gain‐of‐function Akt, suggesting the inhibition of myogenesis in C2C12 cells by PPB was through its dephosphorylation of Akt.