We previously reported that the four-transmembrane L6 family member 5 (TM4SF5) was highly expressed in hepatocarcinoma, induced morphological elongation and epithelialmesenchymal transition, and caused abnormal cell growth in multilayers in vitro and tumor formation in vivo. In this study, we identified a synthetic compound, 4 -(p-toluenesulfonylamido)-4-hydroxychalcone (TSAHC) that antagonized both the TM4SF5-mediated multilayer growth and TM4SF5-enhanced migration/invasion. TSAHC treatment induced multilayer-growing cells to grow in monolayers, recovering contact inhibition without accompanying apoptosis, and inhibited chemotactic migration and invasion. E pithelial monolayer integrity is maintained by integrin-mediated cell adhesion between the cell and the extracellular matrix (ECM) and by E-cadherin-mediated contact between adjacent cells. 1 Epithelial-mesenchymal transition (EMT) through loss of cellcell contacts disrupts monolayer integrity and alters cell-ECM interactions. 2 Tumor cells disseminated from primary tumors via loss of cell adhesion and contact can migrate to and invade distal tissues. 3 We recently reported that TM4SF5-mediated EMT results in a loss of contact inhibition and multilayer growth. 4 Therefore, altered cell adhesion and contact may lead to both a loss of contact inhibition and a dissemination of metastatic cells from the primary tumor. 5 Integrin-mediated cell adhesion reorganizes actin filaments 6 through activation of diverse intracellular signaling molecules, including focal adhesion kinase (FAK), Rho guanosine triphosphatases (RhoA, Rac1, and CDC42), and others, 7 which are critical for cellular morphology and migration. 8 TM4SF proteins (i.e., tetraspanins or tetraspans) are a group of membrane proteins with four transmembrane

Furthermore, wildtype Akt1, but not the S473A mutant, appeared to be associated with 3 OGT following glucosamine treatment. Together, these observations suggest that Akt1 Ser473 may undergo both phosphorylation and O-GlcNAc modification, and the balance between these may regulate murine β-pancreatic cell fate.

SummaryTransmembrane 4 L six family member 5 (TM4SF5) plays an important role in cell migration, and focal adhesion kinase (FAK) activity is essential for homeostatic and pathological migration of adherent cells. However, it is unclear how TM4SF5 signaling mediates the activation of cellular migration machinery, and how FAK is activated during cell adhesion. Here, we showed that direct and adhesiondependent binding of TM4SF5 to FAK causes a structural alteration that may release the inhibitory intramolecular interaction in FAK. In turn, this may activate FAK at the cell's leading edge, to promote migration/invasion and in vivo metastasis. TM4SF5-mediated FAK activation occurred during integrin-mediated cell adhesion. TM4SF5 was localized at the leading edge of the cells, together with FAK and actin-organizing molecules, indicating a signaling link between TM4SF5/FAK and actin reorganization machinery. Impaired interactions between TM4SF5 and FAK resulted in an attenuated FAK phosphorylation (the signaling link to actin organization machinery) and the metastatic potential. Our findings demonstrate that TM4SF5 directly binds to and activates FAK in an adhesiondependent manner, to regulate cell migration and invasion, suggesting that TM4SF5 is a promising target in the treatment of metastatic cancer.

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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.