title: Adaptor protein Crk induces Src-dependent activation of p38 MAPK in regulation of synovial sarcoma cell proliferation.
abstract: The adaptor protein Crk mediates intracellular signaling related to cell motility and proliferation and is implicated in human tumorigenesis. The role of Crk in the growth of human sarcoma has remained unclear, however. The present study shows that Crk-induced activation of Src and subsequent signaling by p38 mitogen-activated protein kinase (MAPK) contribute to the enhanced proliferation of human synovial sarcoma cells. Depletion of Crk by RNA interference markedly inhibited proliferation of the synovial sarcoma cell lines HS-SYII, SYO-1, and Fuji as well as prevented anchorage-independent growth. Conversely, reconstitution with CrkII by authentic small interfering RNA-resistant Crk gene restored proliferation in Crk-silenced SYO-1 cells. Crk-depleted synovial sarcoma cells manifested enhanced transcriptional activity and expression of the p16(INK4A) gene, resulting in their accumulation in G(1) phase of the cell cycle. In response to hepatocyte growth factor stimulation, Crk prominently induced the tyrosine phosphorylation of Grb2-associated binder 1 through activation of Src and focal adhesion kinase, and the Src family kinase inhibitor PP2 almost completely inhibited the proliferation of SYO-1 cells. Crk also induced the phosphorylation of p38 MAPK, and SB203580, a p38 MAPK-specific inhibitor, increased expression of p16(INK4A) gene in SYO-1 cells. Furthermore, SB203580 or depletion of p38 MAPK by small interfering RNA suppressed both the phosphorylation of Akt triggered by hepatocyte growth factor and the proliferation of SYO-1 cells. These results suggest that Crk promotes proliferation of human synovial sarcoma cells through activation of Src and its downstream signaling by a novel p38 MAPK-Akt pathway, with these signaling molecules providing potent new targets for molecular therapeutics.
authors.affiliation: Department of Orthopedic Surgery, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Watanabe
authors.forename: Masumi
authors.initials: M
authors.lastname: Tsuda
authors.forename: Shinya
authors.initials: S
authors.lastname: Tanaka
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Ohba
authors.forename: Hideaki
authors.initials: H
authors.lastname: Kawaguchi
authors.forename: Tokifumi
authors.initials: T
authors.lastname: Majima
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Sawa
authors.forename: Akio
authors.initials: A
authors.lastname: Minami
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D002453:Cell Cycle / Q000502:physiology; D048708:Cell Growth Processes / Q000502:physiology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D051379:Mice; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D050737:Proto-Oncogene Proteins c-crk / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D013584:Sarcoma, Synovial / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D014443:Tyrosine / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D018909:src Homology Domains; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C485285:CRK protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; C099818:DOCK1 protein, human; C098587:GAB1 protein, human; D050737:Proto-Oncogene Proteins c-crk; D014443:Tyrosine; D019061:src-Family Kinases; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; D020744:rac GTP-Binding Proteins