The COOH-terminus of TM4SF5 in hepatoma cell lines regulates c-Src to form invasive protrusions via EGFR Tyr845 phosphorylation

AbstractTransmembrane 4 L six family member 5 (TM4SF5) enhances cell migration and invasion, although how TM4SF5 mechanistically mediates these effects remains unknown. In the study, during efforts to understand TM4SF5-mediated signal transduction, TM4SF5 was shown to bind c-Src and thus hepatoma cell lines expressing TM4SF5 were analyzed for the significance of the interaction in cell invasion. The C-terminus of TM4SF5 bound both inactive c-Src that might be sequestered to certain cellular areas and active c-Src that might form invasive protrusions. Wildtype (WT) TM4SF5 expression enhanced migration and invasive protrusion formation in a c-Src-dependent manner, compared with TM4SF5-null control hepatoma cell lines. However, tailless TM4SF5ΔC cells were more efficient than WT TM4SF5 cells, suggesting a negative regulatory role by the C-terminus. TM4SF5 WT- or TM4SF5ΔC-mediated formation of invasive protrusions was dependent or independent on serum or epidermal growth factor treatment, respectively, although they both were dependent on c-Src. The c-Src activity of TM4SF5 WT- or TM4SF5ΔC-expressing cells correlated with enhanced Tyr845 phosphorylation of epidermal growth factor receptor. Y845F EGFR mutation abolished the TM4SF5-mediated invasive protrusions, but not c-Src phosphorylation. Our findings demonstrate that TM4SF5 modulates c-Src activity during TM4SF5-mediated invasion through a TM4SF5/c-Src/EGFR signaling pathway, differentially along the leading protrusive edges of an invasive cancer cell

JNK signaling activity regulates cell-cell adhesions via TM4SF5-mediated p27Kip1 phosphorylation

Transmembrane 4 L six family member 5 (TM4SF5) can regulate cell–cell adhesion and cellular morphology via cytoplasmic p27Kip1-mediated changes in RhoA activity. However, how TM4SF5 causes cytosolic p27Kip1 stabilization remains unknown. In this study we found that TM4SF5-mediated Ser10 phosphorylation of p27Kip1 required for cytosolic localization was not always correlated with Akt activity. Inhibition or suppression of c-Jun Nterminal kinase (JNK) in TM4SF5-expressing cells decreased Ser10 phosphorylation of p27Kip1 and rescued expression levels and localization of adherence junction molecules to cell–cell contacts. These observations suggest involvement of JNKs in TM4SF5-mediated p27Kip1 Ser10 phosphorylation and localization during epithelial–mesenchymal transition.OAIID:oai:osos.snu.ac.kr:snu2012-01/102/0000003910/2SEQ:2PERF_CD:SNU2012-01EVAL_ITEM_CD:102USER_ID:0000003910ADJUST_YN:NEMP_ID:A078142DEPT_CD:375CITE_RATE:4.238FILENAME:63HJK-CL.pdfDEPT_NM:약학과EMAIL:[email protected]:

TM4SF5 accelerates G1/S phase progression via cytosolic p27Kip1 expression and RhoA activity

Transmembrane 4 L six family member 5 (TM4SF5) causes epithelial–mesenchymal transition (EMT) for aberrant cell proliferation. However, the effects of TM4SF5 expression on cell cycle are unknown so far. In this study, using hepatocytes that either ectopically or endogenously express TM4SF5 and human hepatocarcinoma tissues, the role of TM4SF5 in G1/S phase progression was examined. We found that TM4SF5 expression accelerated G1/S phase progression with facilitated cyclin D1 and E expression and Rb phosphorylation. Furthermore, TM4SF5 enhanced trafficking of CDK4 and cyclin D1 into the nucleus and induced complex formation between them. However, TM4SF5-facilitated G1/S phase progression was blocked by silencing of p27Kip1 using siRNA or by infection of active RhoA. Pharmacological inhibition of ROCK accelerated the G1/S phase progression of control TM4SF5-unexpressing cells. Altogether, these observations suggest that TM4SF5 accelerates G1/S phase progression with facilitated CDK4/cyclin D1 entry into the nucleus, which might be supported by TM4SF5-mediated actin reorganization through cytosolic p27Kip1 expression and Rho GTPase activity.OAIID:oai:osos.snu.ac.kr:snu2010-01/102/0000003910/4SEQ:4PERF_CD:SNU2010-01EVAL_ITEM_CD:102USER_ID:0000003910ADJUST_YN:NEMP_ID:A078142DEPT_CD:375CITE_RATE:4.733FILENAME:56KHJ_BBAMCR.pdfDEPT_NM:약학과EMAIL:[email protected]:

Differential inhibition of transmembrane 4 L six family member 5 (TM4SF5)-mediated tumorigenesis by TSAHC and sorafenib

Two separate clinical studies of advanced hepatocarcinoma patients recently reported that the multikinase inhibitor sorafenib (nexavar) could extend survival of the patients only by 2-3 months. We also previously demonstrated that 4`-(p-toluenesulfonylamido)-4-hydroxychalcone (TSAHC) blocks the multilayer growth and migration mediated by TM4SF5, which is highly expressed in approximately 80% of Korean hepatocarcinoma patients. Therefore, we wondered how TSAHC might be different from sorafenib to deal with hepatocarcinoma in terms of the therapeutic characteristics including specificity for TM4SF5. TM4SF5 is previously shown to mediate tumorigenesis through cytosolic p27(Kip1)-mediated inactivation of RhoA, epithelial-mesenchymal transition, multilayer growth, migration, invasion and tumor angiogenesis. In this study, TSAHC and two derivatives showed similar antagonistic activities against TM4SF5-mediated signaling and multilayer growth in vitro and anti-tumorigenic activity even in early stages of TM4SF5-mediated tumor formation in nude mice. Meanwhile, sorafenib was only effective much later in tumorigenesis in vivo and affected in vitro proliferation in a TM4SF5-independent manner. Altogether, these observations suggest that TSAHC may be a promising anti-tumorigenic reagent, especially against TM4SF5-mediated hepatocarcinoma.

N-terminus-independent activation of c-Src via binding to a tetraspan(in) TM4SF5 in hepatocellular carcinoma is abolished by the TM4SF5 C-terminal peptide application

Active c-Src non-receptor tyrosine kinase localizes to the plasma membrane via N-terminal lipid modification. Membranous c-Src causes cancer initiation and progression. Even though transmembrane 4 L six family member 5 (TM4SF5), a tetraspan(in), can be involved in this mechanism, the molecular and structural influence of TM4SF5 on c-Src remains unknown. Methods: Here, we investigated molecular and structural details by which TM4SF5 regulated c-Src devoid of its N-terminus and how cell-penetrating peptides were able to interrupt c-Src activation via interference of c-Src-TM4SF5 interaction in hepatocellular carcinoma models. Results: The TM4SF5 C-terminus efficiently bound the c-Src SH1 kinase domain, efficiently to the inactively-closed form. The complex involved protein tyrosine phosphatase 1B able to dephosphorylate Tyr530. The c-Src SH1 domain alone, even in a closed form, bound TM4SF5 to cause c-Src Tyr419 and FAK Y861 phosphorylation. Homology modeling and molecular dynamics simulation studies predicted the directly interfacing residues, which were further validated by mutational studies. Cell penetration of TM4SF5 C-terminal peptides blocked the interaction of TM4SF5 with c-Src and prevented c-Src-dependent tumor initiation and progression in vivo. Conclusions: Collectively, these data demonstrate that binding of the TM4SF5 C-terminus to the kinase domain of inactive c-Src leads to its activation. Because this binding can be abolished by cell-penetrating peptides containing the TM4SF5 C-terminus, targeting this direct interaction may be an effective strategy for developing therapeutics that block the development and progression of hepatocellular carcinoma.Y

Cross-talk between TGFβ1 and EGFR signaling pathways induces TM4SF5 expression and Epithelial-Mesenchymal Transition.

The EMT (epithelial–mesenchymal transition) is involved in fibrosis and cancer, and is regulated by different signalling pathways mediated through soluble factors, actin reorganization and transcription factor actions. Because the tetraspan (also called tetraspanin) TM4SF5 (transmembrane 4 L6 family member 5) is highly expressed in hepatocellular carcinoma and induces EMT, understanding how TM4SF5 expression in hepatocytes is regulated is important. We explored the mechanisms that induce TM4SF5 expression and whether impaired signalling pathways for TM4SF5 expression inhibit the acquisition of mesenchymal cell features, using human and mouse normal hepatocytes. We found that TGFβ1 (transforming growth factor β1)-mediated Smad activation caused TM4SF5 expression and EMT, and activation of the EGFR [EGF (epidermal growth factor) receptor] pathway. Inhibition of EGFR activity following TGFβ1 treatment abolished acquisition of EMT, suggesting a link from Smads to EGFR for TM4SF5 expression. Further, TGFβ1-mediated EGFR activation and TM4SF5 expression were abolished by EGFR suppression or extracellular EGF depletion. Smad overexpression mediated EGFR activation and TM4SF5 expression in the absence of serum, and EGFR kinase inactivation or EGF depletion abolished Smad-overexpression-induced TM4SF5 and mesenchymal cell marker expression. Inhibition of Smad, EGFR or TM4SF5 using Smad7 or small compounds also blocked TM4SF5 expression and/or EMT. These results indicate that TGFβ1- and growth factor-mediated signalling activities mediate TM4SF5 expression leading to acquisition of mesenchymal cell features, suggesting that TM4SF5 induction may be involved in the development of liver pathologies.OAIID:oai:osos.snu.ac.kr:snu2012-01/102/0000003910/3SEQ:3PERF_CD:SNU2012-01EVAL_ITEM_CD:102USER_ID:0000003910ADJUST_YN:NEMP_ID:A078142DEPT_CD:375CITE_RATE:4.897FILENAME:66MKK-BJ.pdfDEPT_NM:약학과EMAIL:[email protected]_YN:YCONFIRM:

Glucosamine Treatment-mediated O-GlcNAc Modification of Paxillin Depends on Adhesion State of Rat Insulinoma INS-1 Cells*

Protein-protein interactions and/or signaling activities at focal adhesions, where integrin-mediated adhesion to extracellular matrix occurs, are critical for the regulation of adhesion-dependent cellular functions. Although the phosphorylation and activities of focal adhesion molecules have been intensively studied, the effects of the O-GlcNAc modification of their Ser/Thr residues on cellular functions have been largely unexplored. We investigated the effects of O-GlcNAc modification on actin reorganization and morphology of rat insulinoma INS-1 cells after glucosamine (GlcN) treatment. We found that paxillin, a key adaptor molecule in focal adhesions, could be modified by O-GlcNAc in INS-1 cells treated with GlcN and in pancreatic islets from mice treated with streptozotocin. Ser-84/85 in human paxillin appeared to be modified by O-GlcNAc, which was inversely correlated to Ser-85 phosphorylation (Ser-83 in rat paxillin). Integrin-mediated adhesion signaling inhibited the GlcN treatment-enhanced O-GlcNAc modification of paxillin. Adherent INS-1 cells treated with GlcN showed restricted protrusions, whereas untreated cells showed active protrusions for multiple-elongated morphologies. Upon GlcN treatment, expression of a triple mutation (S83A/S84A/S85A) resulted in no further restriction of protrusions. Together these observations suggest that murine pancreatic β cells may have restricted actin organization upon GlcN treatment by virtue of the O-GlcNAc modification of paxillin, which can be antagonized by a persistent cell adhesion process