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Cellular settings mediating Src Substrate switching between focal adhesion kinase tyrosine 861 and CUB-domain-containing protein 1 (CDCP1) tyrosine 734.

ABSTRACT: Reciprocal interactions between Src family kinases (SFKs) and focal adhesion kinase (FAK) are critical during changes in cell attachment. Recently it has been recognized that another SFK substrate, CUB-domain-containing protein 1 (CDCP1), is differentially phosphorylated during these events. However, the molecular processes underlying SFK-mediated phosphorylation of CDCP1 are poorly understood. Here we identify a novel mechanism in which FAK tyrosine 861 and CDCP1-Tyr-734 compete as SFK substrates and demonstrate cellular settings in which SFKs switch between these sites. Our results show that stable CDCP1 expression induces robust SFK-mediated phosphorylation of CDCP1-Tyr-734 with concomitant loss of p-FAK-Tyr-861 in adherent HeLa cells. SFK substrate switching in these cells is dependent on the level of expression of CDCP1 and is also dependent on CDCP1-Tyr-734 but is independent of CDCP1-Tyr-743 and -Tyr-762. In HeLa CDCP1 cells, engagement of SFKs with CDCP1 is accompanied by an increase in phosphorylation of Src-Tyr-416 and a change in cell morphology to a fibroblastic appearance dependent on CDCP1-Tyr-734. SFK switching between FAK-Tyr-861 and CDCP1-Tyr-734 also occurs during changes in adhesion of colorectal cancer cell lines endogenously expressing these two proteins. Consistently, increased p-FAK-Tyr-861 levels and a more epithelial morphology are seen in colon cancer SW480 cells silenced for CDCP1. Unlike protein kinase Cδ, FAK does not appear to form a trimeric complex with Src and CDCP1. These data demonstrate novel aspects of the dynamics of SFK-mediated cell signaling that may be relevant during cancer progression.

SUBMITTER: Wortmann A

PROVIDER: S-EPMC3234987 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundDeregulated expression of the transmembrane glycoprotein CDCP1 (CUB domain-containing protein-1) has been detected in several cancers including colon, lung, gastric, breast, and pancreatic carcinomas. CDCP1 has been proposed to either positively or negatively regulate tumour metastasis. In this study we assessed the role of CDCP1 in properties of cells that are directly relevant to metastasis, namely adhesion and motility. In addition, association between CDCP1 and the tetraspanin protein CD9 was investigated.MethodsCDCP1 and CD9 protein expression was measured in a series of colon cancer cell lines by flow cytometry and Western blotting. Adhesion of Colo320 and SW480 cells was determined using a Matrigel adhesion assay. The chemotactic motility of SW480 cells in which CDCP1 expression had been reduced by RNA interference was analysed using the xCELLigence system Real-Time Cell Analyzer Dual Plates combined with 8 μm pore filters. Detergent-resistant membrane fractions were generated following density gradient centrifugation and the CDCP1 and CD9 protein composition of these fractions was determined by Western blotting. The potential association of the CDCP1 and CD9 proteins was assessed by co-immunoprecipitation.ResultsEngineered CDCP1 expression in Colo320 cells resulted in a reduction in cell adhesion to Matrigel. Treatment of SW480 cells with CDCP1 siRNA reduced serum-induced chemotaxis. CDCP1 and CD9 cell-surface protein and mRNA levels showed a positive correlation in colon cancer cell lines and the proteins formed a low-level, but detectable complex as judged by co-sedimentation of detergent lysates of HT-29 cells in sucrose gradients as well as by co-immunoprecipitation in SW480 cell lysates.ConclusionsA number of recent studies have assigned a potentially important role for the cell-surface protein CDCP1 in invasion and metastasis of a several types of human cancer cells. In this study, CDCP1 was shown to modulate cell-substratum adhesion and motility in colon cancer cell lines, with some variation depending on the colon cancer cell type. CDCP1 and CD9 were co-expressed at the mRNA and protein level and we obtained evidence for the presence of a molecular complex of these proteins in SW480 colon cancer cells.

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Cellular settings mediating Src Substrate switching between focal adhesion kinase tyrosine 861 and CUB-domain-containing protein 1 (CDCP1) tyrosine 734.

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