title: Axin inhibits extracellular signal-regulated kinase pathway by Ras degradation via beta-catenin.
abstract: Interactions between the Wnt/beta-catenin and the extracellular signal-regulated kinase (ERK) pathways have been posited, but the molecular mechanisms and cooperative roles of such interaction in carcinogenesis are poorly understood. In the present study, the Raf-1, MEK, and ERK activities were concomitantly decreased in fibroblasts, which inhibit morphological transformation and proliferation by Axin induction. The inhibition of the components of the ERK pathway by Axin occurred in cells retaining wild-type beta-catenin, including primary hepatocytes, but not in cells retaining non-degradable mutant beta-catenin. Axin inhibits cellular proliferation and ERK pathway activation induced by either epidermal growth factor or Ras, indicating a role of Axin in the regulation of growth induced by ERK pathway activation. ERK pathway regulation by Axin occurs at least partly via reduction of the protein level of Ras. Both wild-type and mutant Ras proteins are subjected to regulation by Axin, which occurs in cells retaining wild-type but not mutant beta-catenin gene. The role of beta-catenin in the regulation of the Ras-ERK pathway was further confirmed by Ras reduction and subsequent inhibitions of the ERK pathway components by knock down of mutated form of beta-catenin. The Ras regulation by Axin was blocked by treatment of leupeptin, an inhibitor of the lysosomal protein degradation machinery. Overall, Axin inhibits proliferation of cells at least partly by reduction of Ras protein level via beta-catenin. This study provides evidences for the role of the Ras-ERK pathway in carcinogenesis caused by mutations of the Wnt/beta-catenin pathway components.
authors: National Research Laboratory of Molecular Complex Control, and Department of Biotechnology, Yonsei University, Seoul, Korea.
authors: Soung Hoo
authors: SH
authors: Jeon
authors: Ju-Yong
authors: JY
authors: Yoon
authors: Young-Nyun
authors: YN
authors: Park
authors: Woo-Jeong
authors: WJ
authors: Jeong
authors: Sewoon
authors: S
authors: Kim
authors: Eek-Hoon
authors: EH
authors: Jho
authors: Young-Joon
authors: YJ
authors: Surh
authors: Kang-Yell
authors: KY
authors: Choi
mesh_terms: D000818:Animals; D060466:Axin Protein; D002448:Cell Adhesion; D002453:Cell Cycle; D049109:Cell Proliferation; D003114:Colony-Forming Units Assay; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005786:Gene Expression Regulation; D022781:Hepatocytes / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D041681:NIH 3T3 Cells / Q000378:metabolism; D015689:Oncogene Protein p21(ras) / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D012097:Repressor Proteins / Q000494:pharmacology*; D015398:Signal Transduction; D051153:Wnt Proteins / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D060466:Axin Protein; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D051153:Wnt Proteins; D051176:beta Catenin; D004815:Epidermal Growth Factor; C483803:Egfr protein, rat; D066246:ErbB Receptors; D019908:Proto-Oncogene Proteins c-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; D015689:Oncogene Protein p21(ras)