title: Amino acids interfere with the ERK1/2-dependent control of macroautophagy by controlling the activation of Raf-1 in human colon cancer HT-29 cells.
abstract: Activation of ERK1/2 stimulates macroautophagy in the human colon cancer cell line HT-29 by favoring the phosphorylation of the Galpha-interacting protein (GAIP) in an amino acid-dependent manner (Ogier-Denis, E., Pattingre, S., El Benna, J., and Codogno, P. (2000) J. Biol. Chem. 275, 39090-39095). Here we show that ERK1/2 activation by aurintricarboxylic acid (ATA) treatment induces the phosphorylation of GAIP in an amino acid-dependent manner. Accordingly, ATA challenge increased the rate of macroautophagy, whereas epidermal growth factor did not significantly affect macroautophagy and GAIP phosphorylation status. In fact, ATA activated the ERK1/2 signaling pathway, whereas epidermal growth factor stimulated both the ERK1/2 pathway and the class I phosphoinositide 3-kinase pathway, known to decrease the rate of macroautophagy. Amino acids interfered with the ATA-induced macroautophagy by inhibiting the activation of the kinase Raf-1. The role of the Ras/Raf-1/ERK1/2 signaling pathway in the GAIP- and amino acid-dependent control of macroautophagy was confirmed in HT-29 cells expressing the Ras(G12V,T35S) mutant. Similar to the protein phosphatase 2A inhibitor okadaic acid, amino acids sustained the phosphorylation of Ser(259), which is involved in the negative regulation of Raf-1. In conclusion, these results add a novel target to the amino acid signaling-dependent control of macroautophagy in intestinal cells.
authors.affiliation: INSERM U504, Glycobiologie et Signalisation Cellulaire, 16, avenue Paul-Vaillant-Couturier, 94807 Villejuif Cedex, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Pattingre
authors.forename: Chantal
authors.initials: C
authors.lastname: Bauvy
authors.forename: Patrice
authors.initials: P
authors.lastname: Codogno
mesh_terms: D001312:Aurintricarboxylic Acid / Q000494:pharmacology; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism*; D020710:RGS Proteins; D014407:Tumor Cells, Cultured
chemical_list: D010750:Phosphoproteins; D020710:RGS Proteins; C097187:regulator of G-protein signalling 19; D001312:Aurintricarboxylic Acid; D019908:Proto-Oncogene Proteins c-raf; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases