title: c-Src-induced activation of ceramide metabolism impairs membrane microdomains and promotes malignant progression by facilitating the translocation of c-Src to focal adhesions.
abstract: The proto-oncogenic tyrosine kinase c-Src is up-regulated in various human cancers, implicating its role in tumour progression. Upon activation, c-Src translocates to focal adhesions and initiates intracellular signalling cascades that promote malignant transformation, but the underlying mechanisms for c-Src translocation remain unclear. In the present study we show that c-Src up-regulation perturbs sphingolipid/cholesterol-enriched membrane microdomains by activating ceramide synthesis, resulting in promotion of c-Src translocation. Using an inducible c-Src expression system in Csk (C-terminal Src kinase)-deficient fibroblasts, we found that translocation of c-Src to focal adhesions/podosomes occurs in the later stages of cell transformation. Activated c-Src is liberated from microdomains and promotes the phosphorylation of FAK (focal adhesion kinase) and cortactin localized to focal adhesions/podosomes. In parallel with these events, anabolic metabolism of ceramides is activated by up-regulation of the de novo synthesis pathway. Inhibition of ceramide conversion into glucosylceramide promotes liberation of c-Src from microdomains, and inhibition of de novo ceramide synthesis restores the microdomain distribution of c-Src and suppresses malignant phenotypes such as increased cell motility and anchorage-independent cell growth. These results suggest that c-Src-induced activation of ceramide synthesis impairs the integrity of microdomains and contributes to malignant progression by promoting the translocation of c-Src to focal adhesions/podosomes.
authors.affiliation: *Department of Oncogene Research, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Kajiwara
authors.affiliation: †Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Yamada
authors.affiliation: †Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Bamba
authors.affiliation: †Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Eiichiro
authors.initials: E
authors.lastname: Fukusaki
authors.affiliation: ‡Department of Molecular Biology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Imamoto
authors.affiliation: *Department of Oncogene Research, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Okada
authors.affiliation: *Department of Oncogene Research, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Chitose
authors.initials: C
authors.lastname: Oneyama
mesh_terms: D000818:Animals; D002471:Cell Transformation, Neoplastic; D002518:Ceramides / Q000378:metabolism*; D022001:Focal Adhesions; D021962:Membrane Microdomains / Q000502:physiology*; D051379:Mice; D015688:Oncogene Protein pp60(v-src) / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D002518:Ceramides; D015688:Oncogene Protein pp60(v-src)