title: M-COPA suppresses endolysosomal Kit-Akt oncogenic signalling through inhibiting the secretory pathway in neoplastic mast cells.
abstract: Gain-of-function mutations in Kit receptor tyrosine kinase result in the development of a variety of cancers, such as mast cell tumours, gastrointestinal stromal tumours (GISTs), acute myeloid leukemia, and melanomas. The drug imatinib, a selective inhibitor of Kit, is used for treatment of mutant Kit-positive cancers. However, mutations in the Kit kinase domain, which are frequently found in neoplastic mast cells, confer an imatinib resistance, and cancers expressing the mutants can proliferate in the presence of imatinib. Recently, we showed that in neoplastic mast cells that endogenously express an imatinib-resistant Kit mutant, Kit causes oncogenic activation of the phosphatidylinositol 3-kinase-Akt (PI3K-Akt) pathway and the signal transducer and activator of transcription 5 (STAT5) but only on endolysosomes and on the endoplasmic reticulum (ER), respectively. Here, we show a strategy for inhibition of the Kit-PI3K-Akt pathway in neoplastic mast cells by M-COPA (2-methylcoprophilinamide), an inhibitor of this secretory pathway. In M-COPA-treated cells, Kit localization in the ER is significantly increased, whereas endolysosomal Kit disappears, indicating that M-COPA blocks the biosynthetic transport of Kit from the ER. The drug greatly inhibits oncogenic Akt activation without affecting the association of Kit with PI3K, indicating that ER-localized Kit-PI3K complex is unable to activate Akt. Importantly, M-COPA but not imatinib suppresses neoplastic mast cell proliferation through inhibiting anti-apoptotic Akt activation. Results of our M-COPA treatment assay show that Kit can activate Erk not only on the ER but also on other compartments. Furthermore, Tyr568/570, Tyr703, Tyr721, and Tyr936 in Kit are phosphorylated on the ER, indicating that these five tyrosine residues are all phosphorylated before mutant Kit reaches the plasma membrane (PM). Our study provides evidence that Kit is tyrosine-phosphorylated soon after synthesis on the ER but is unable to activate Akt and also demonstrates that M-COPA is efficacious for growth suppression of neoplastic mast cells.
authors.affiliation: Division of Immunobiology, Research Institute for Biomedical Sciences, Tokyo University of Science, Noda, Chiba, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Hara
authors.affiliation: Division of Immunobiology, Research Institute for Biomedical Sciences, Tokyo University of Science, Noda, Chiba, Japan.
authors.forename: Yuuki
authors.initials: Y
authors.lastname: Obata
authors.affiliation: Division of Immunobiology, Research Institute for Biomedical Sciences, Tokyo University of Science, Noda, Chiba, Japan.
authors.forename: Keita
authors.initials: K
authors.lastname: Horikawa
authors.affiliation: Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Shinjuku-ku, Tokyo, Japan.
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Tasaki
authors.affiliation: Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Shinjuku-ku, Tokyo, Japan.
authors.forename: Kyohei
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Shinjuku-ku, Tokyo, Japan.
authors.forename: Takatsugu
authors.initials: T
authors.lastname: Murata
authors.affiliation: Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Shinjuku-ku, Tokyo, Japan.
authors.forename: Isamu
authors.initials: I
authors.lastname: Shiina
authors.affiliation: Division of Immunobiology, Research Institute for Biomedical Sciences, Tokyo University of Science, Noda, Chiba, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Abe
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor; D011992:Endosomes / Q000201:enzymology; D004789:Enzyme Activation; D006801:Humans; D000068877:Imatinib Mesylate / Q000494:pharmacology; D008247:Lysosomes / Q000201:enzymology; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D009284:Naphthols / Q000494:pharmacology*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology*; D055571:Secretory Pathway / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D000970:Antineoplastic Agents; C573938:N-(pyridine-3-ylmethyl)-5-(7-hydroxy-2,6,8-trimethyl-1,2,4a,5,6,7,8,8a-octahydronaphthalene-1-yl)-2-methylpenta-2,4-dienamide; D009284:Naphthols; D011725:Pyridines; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit; D051057:Proto-Oncogene Proteins c-akt