title: Inhibition of the Ras-ERK pathway in mitotic COS7 cells is due to the inability of EGFR/Raf to transduce EGF signaling to downstream proteins.
abstract: Although previous studies have shown that Ras-ERK signaling in mitosis is closed due to the inhibition of signal transduction, the events involved in the molecular mechanisms are still unclear. In the present study, we investigated the Ras-ERK signaling pathway in mitotic COS7 cells. The results demonstrated that treatment with epidermal growth factor (EGF) failed to increase the endocytosis of EGF-EGFR (EGF receptor) complexes in mitotic COS7 cells, although a large amount of endosomes were found in asynchronous COS7 cells. Clathrin expression levels in mitotic COS7 cells were inhibited whereas caveolin expression levels in mitotic COS7 cells were almost unaffected. Y1068 and Y1086 residues of EGFR in the mitotic COS7 cells were activated. However, Grb2 and Shc in the mitotic COS7 cells did not bind to activated EGFR. Ras activity was inhibited in the mitotic COS7 cells whereas its downstream protein, Raf, was obviously phosphorylated by EGF in mitosis. Treatment with phorbol 12-myristate 13-acetate (PMA) also increased the phosphorylation levels of Raf in the mitotic COS7 cells. Nevertheless, Raf phosphorylation in mitosis was significantly inhibited by AG1478. Lastly, activation of EGF-mediated MEK and ERK in the mitotic COS7 cells was obviously inhibited. In summary, our results suggest that the Ras-ERK pathway is inhibited in mitotic COS7 cells which may be the dual result of the difficulty in the transduction of EGF signaling by EGFR or Raf to downstream proteins.
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, P.R. China.
authors.forename: Huaiping
authors.initials: H
authors.lastname: Shi
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, P.R. China.
authors.forename: Tianying
authors.initials: T
authors.lastname: Zhang
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, P.R. China.
authors.forename: Yongqing
authors.initials: Y
authors.lastname: Yi
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, P.R. China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Ma
mesh_terms: D000818:Animals; D019556:COS Cells; D022461:Caveolins / Q000096:biosynthesis; D002460:Cell Line; D002522:Chlorocebus aethiops; D002966:Clathrin / Q000096:biosynthesis; D004705:Endocytosis / Q000502:physiology; D011992:Endosomes / Q000502:physiology; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D051380:GRB2 Adaptor Protein / Q000378:metabolism; D020935:MAP Kinase Signaling System; D015739:Nocodazole / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D011799:Quinazolines / Q000494:pharmacology; D055765:Shc Signaling Adaptor Proteins / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D020032:Tyrphostins / Q000494:pharmacology; D048490:raf Kinases / Q000378:metabolism*
chemical_list: D022461:Caveolins; D002966:Clathrin; D051380:GRB2 Adaptor Protein; D011799:Quinazolines; D055765:Shc Signaling Adaptor Proteins; D020032:Tyrphostins; C101044:RTKI cpd; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D019908:Proto-Oncogene Proteins c-raf; D048490:raf Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D016283:Proto-Oncogene Proteins p21(ras); D013755:Tetradecanoylphorbol Acetate; D015739:Nocodazole