title: Chk1 phosphorylates the tumour suppressor Mig-6, regulating the activation of EGF signalling.
abstract: 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.
authors.affiliation: Department of Molecular Biology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan.
authors.forename: Ning
authors.initials: N
authors.lastname: Liu
authors.forename: Masaki
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Kyoko
authors.initials: K
authors.lastname: Kitagawa
authors.forename: Yojiro
authors.initials: Y
authors.lastname: Kotake
authors.forename: Sayuri
authors.initials: S
authors.lastname: Suzuki
authors.forename: Senji
authors.initials: S
authors.lastname: Shirasawa
authors.forename: Keiichi I
authors.initials: KI
authors.lastname: Nakayama
authors.forename: Makoto
authors.initials: M
authors.lastname: Nakanishi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Niida
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Kitagawa
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism*; D019943:Amino Acid Substitution; D000071877:Checkpoint Kinase 1; D004815:Epidermal Growth Factor / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D013058:Mass Spectrometry; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D012694:Serine / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C484017:ERRFI1 protein, human; D025521:Tumor Suppressor Proteins; D012694:Serine; D004815:Epidermal Growth Factor; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1