Chk1 phosphorylates the tumour suppressor Mig-6, regulating the activation of EGF signalling

The tumour suppressor gene product Mig‐6 acts as an inhibitor of epidermal growth factor (EGF) signalling. However, its posttranslational modifications and regulatory mechanisms have not been elucidated. Here, we investigated the phosphorylation of human Mig‐6 and found that Chk1 phosphorylated Mig‐...

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Bibliographic Details
Published in:The EMBO journal 2012-05, Vol.31 (10), p.2365-2377
Main Authors: Liu, Ning, Matsumoto, Masaki, Kitagawa, Kyoko, Kotake, Yojiro, Suzuki, Sayuri, Shirasawa, Senji, Nakayama, Keiichi I, Nakanishi, Makoto, Niida, Hiroyuki, Kitagawa, Masatoshi
Format: Article
Language:English
Subjects:
Adaptor Proteins, Signal Transducing - chemistry
Adaptor Proteins, Signal Transducing - metabolism
Amino Acid Substitution
Cancer
Cell growth
Checkpoint Kinase 1
Chk1
EGFR
Epidermal growth factor
Epidermal Growth Factor - metabolism
Gene Expression Regulation
Humans
Mass Spectrometry
Mig-6
Molecular biology
Mutagenesis, Site-Directed
Phosphorylation
Protein Kinases - metabolism
Serine - genetics
Serine - metabolism
Signal Transduction
Tumor Suppressor Proteins - chemistry
Tumor Suppressor Proteins - metabolism
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Summary:The tumour suppressor gene product Mig‐6 acts as an inhibitor of epidermal growth factor (EGF) signalling. However, its posttranslational modifications and regulatory mechanisms have not been elucidated. Here, we investigated the phosphorylation of human Mig‐6 and found that Chk1 phosphorylated Mig‐6 in vivo as well as in vitro. Moreover, EGF stimulation promoted phosphorylation of Mig‐6 without DNA damage and the phosphorylation was inhibited by depletion of Chk1. EGF also increased Ser280‐phosphorylated Chk1, a cytoplasmic‐tethering form, via PI3K pathway. Mass spectrometric analyses suggested that Ser 251 of Mig‐6 was a major phosphorylation site by Chk1 in vitro and in vivo. Substitution of Ser 251 to alanine increased inhibitory activity of Mig‐6 against EGF receptor (EGFR) activation. Moreover, EGF‐dependent activation of EGFR and cell growth were inhibited by Chk1 depletion, and were rescued by co‐depletion of Mig‐6. Our results suggest that Chk1 phosphorylates Mig‐6 on Ser 251, resulting in the inhibition of Mig‐6, and that Chk1 acts as a positive regulator of EGF signalling. This is a novel function of Chk1. While characterizing the EGF receptor (EGFR) feedback inhibitor Mig6 as Chk1 target, this paper provides the first mechanistic explanation for DNA damage‐independent functions of Chk1 in the regulation of growth factor signalling and cellular proliferation.
ISSN:0261-4189
1460-2075
DOI:10.1038/emboj.2012.88