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Summary: Placental trophoblastic cells play important roles in placental development and fetal health. However, the mechanism of trophoblastic cell fusion is still not entirely clear. The level of Tspan5 in the embryo culture medium was detected using enzyme-linked immunosorbent assay (ELISA). Fusion of BeWo cells was observed by immunofluorescence. Cell fusion-related factors and EMT-related factors were identified by qRT-PCR and western blotting. Notch protein repressor DAPT was used to verify the role of Tspan5 in BeWo cells. The expression of Tspan5 was significantly increased in embryo culture medium. The fusion of BeWo cells was observed after treatment with forskolin (FSK). Cell fusion-related factors (i.e. β-hCG and syncytin 1/2) and Tspan5 were significantly increased after FSK treatment. In addition, FSK treatment promoted EMT-related protein expression in BeWo cells. Knockdown of Tspan5 inhibited cell fusion and EMT-related protein levels. Notch-1 and Jagged-1 protein levels were significantly upregulated, and the EMT process was activated by overexpression of Tspan5 in FSK-treated BeWo cells. Interestingly, blocking the Notch pathway by the repressor DAPT had the opposite results. These results indicated that Tspan5 could promote the EMT process by activating the Notch pathway, thereby causing cell fusion. These findings contribute to a better understanding of trophoblast cell syncytialization and embryonic development. Tspan5 may be used as a therapeutic target for normal placental development. [ABSTRACT FROM AUTHOR]

Cancer is a major disease and the leading cause of death worldwide, with colorectal cancer (CRC) being the third-most common cancer in Korea. The survival rate associated with CRC reduces as the disease stage increases. Therefore, its early detection and treatment can greatly increase patient survival rates. In this study, we identified the tetraspanin 5 (TSPAN5) gene as an important biomarker for predicting the prognosis of patients with CRC. A TMA slide was used for statistical analysis. pN and clinical stage were found to be significant factors according to chi-square analysis, whereas pT, pN, metastasis, clinical stage, and TSPAN5 expression were significant according to Cox regression analysis. In order to prove the usefulness of TSPAN5, which is overexpressed in patients with metastatic CRC, as a biomarker, proliferation, migration, invasion, and tumorigenicity were examined using cell lines inhibited using small interfering RNA. The evaluations confirmed that TSPAN5 suppression, in turn, suppressed proliferation, migration, invasion, and tumorigenesis, which are characteristic of cancer cells. Therefore, the evaluation of TSPAN5 expression may help observe the prognosis of CRC and determine an appropriate treatment method for patients with CRC. [ABSTRACT FROM AUTHOR]

MHC molecules are not randomly distributed on the plasma membrane but instead are present in discrete nanoclusters. The mechanisms that control formation of MHC I nanoclusters and the importance of such structures are incompletely understood. Here, we report a molecular association between tetraspanin-5 (Tspan5) and MHC I molecules that started in the endoplasmic reticulum and was maintained on the plasma membrane. This association was observed both in mouse dendritic cells and in human cancer cell lines. Loss of Tspan5 reduced the size of MHC I clusters without affecting MHC I peptide loading, delivery of complexes to the plasma membrane, or overall surface MHC I levels. Functionally, CD8 T cell responses to antigen presented by Tspan5-deficient dendritic cells were impaired but were restored by antibody-induced reclustering of MHC I molecules. In contrast, Tspan5 did not associate with two other plasma membrane proteins, Flotillin1 and CD55, with or the endoplasmic reticulum proteins Tapasin and TAP. Thus, our findings identify a mechanism underlying the clustering of MHC I molecules that is important for optimal T cell responses. [ABSTRACT FROM AUTHOR]

Objective: To study the effect of Tspan5 on the proliferation and migration of trophoblast cell, seeking a new target for the treatment of gestational trophoblastic disease. Materials and Methods: The authors used RNAi to silence the Tspan5 expression in human choriocarcinoma cell line JEG-3 first, and then used Western blotting to detect the expression of Tspan5, calculating the efficiency of interference. CCK-8 test, colony formation, and scratch assay were used to detect the proliferation and migration of the before and after interference JEG-3 cells. Results: Western blotting results showed that Tspan5/NC band gray value was highest and Tspan5/1005 lowest, so the authors chose Tspan5/1005 as an interference group to finish the follow-up experiment. Interference group (Tspan5/1005) clone number of JEG-3 cell was significantly reduced compared with the control group (Tspan5/NC) (148±23 vs. 276±31, p < 0.01). There was no significant difference between blank group and control group (328±39 vs. 276±31, p > 0.1). The JEG-3 cell proliferation activity of blank group was the highest, the control group (Tspan5/NC) group's proliferation activity was slightly lower, however there was no significant difference (1.200 ± 0.103 vs. 1.185 ± 0.022, p > 0.05) between the two. Compared with the control group (Tspan5/NC), the JEG-3 cell proliferation activity of interference group (Tspan5/1005) decreased significantly (1.185 ± 0.022 vs. 1.076 ±0.028, p < 0.01). In the absolute value of the scratch width, 24 hours after scratching minus the scratch width 0 hours after scratching, the interference group (Tspan5/1005) was significantly less than the control group (Tspan5/NC) (1.27 ± 0.03 cm vs. 1.97 ± 0.38 cm, p < 0.05). Conclusion: In this study, the authors found that the proliferation and migration of choriocarcinoma cells were reduced after using RNAi technology to knockdown Tspan5 expression. The quantity of Tspan5 expression was positively related with proliferation and migration of choriocarcinoma cells. [ABSTRACT FROM AUTHOR]

Simple Summary: Hepatocellular carcinoma (HCC) ranks second among the leading causes of cancer-related death. Since current therapeutic options are very limited, a deeper understanding of the molecular mechanisms underlying the tumor onset and progression of HCC holds great potential for improved therapeutic options. Although it has been shown that deleted in liver cancer 1 (DLC1) acts as a tumor suppressor whose allele is lost in 50% of liver cancers, alterations in gene expression initiated by DLC1 loss have not yet been the primary focus of liver cancer research. To identify novel gene targets that allow for a personalized medicine approach for HCC therapy, we performed gene expression profiling for HepG2 cells stably expressing DLC1shRNA. We provide evidence that TSPAN5 is required for HCC growth, migration and invasion, and dissected the underlying molecular mechanisms involving myocardin-related transcription factors. Thus, TSPAN5 represents a novel therapeutic target for the treatment of HCC characterized by DLC1 loss. Human hepatocellular carcinoma (HCC) is among the most lethal and common cancers in the human population, and new molecular targets for therapeutic intervention are urgently needed. Deleted in liver cancer 1 (DLC1) was originally identified as a tumor suppressor gene in human HCC. DLC1 is a Rho-GTPase-activating protein (RhoGAP) which accelerates the return of RhoGTPases to an inactive state. We recently described that the restoration of DLC1 expression induces cellular senescence. However, this principle is not amenable to direct therapeutic targeting. We therefore performed gene expression profiling for HepG2 cells depleted of DLC1 to identify druggable gene targets mediating the effects of DLC1 on senescence induction. This approach revealed that versican (VCAN), tetraspanin 5 (TSPAN5) and N-cadherin (CDH2) were strongly upregulated upon DLC1 depletion in HCC cells, but only TSPAN5 affected the proliferation of HCC cells and human HCC. The depletion of TSPAN5 induced oncogene-induced senescence (OIS), mediated by the p16INK4a/pRb pathways. Mechanistically, silencing TSPAN5 reduced actin polymerization and thereby myocardin-related transcription factor A- filamin A (MRTF-A-FLNA) complex formation, resulting in decreased expression of MRTF/SRF-dependent target genes and senescence induction in vitro and in vivo. Our results identify TSPAN5 as a novel druggable target for HCC. [ABSTRACT FROM AUTHOR]

Tetraspanins are a class of evolutionarily conserved transmembrane proteins with 33 members identified in mammals that have the ability to organize specific membrane domains, named tetraspanin-enriched microdomains (TEMs). Despite the relative abundance of different tetraspanins in the CNS, few studies have explored their role at synapses. Here, we investigate the function of TSPAN5, a member of the tetraspanin superfamily for which mRNA transcripts are found at high levels in the mouse brain. We demonstrate that TSPAN5 is localized in dendritic spines of pyramidal excitatory neurons and that TSPAN5 knockdown induces a dramatic decrease in spine number because of defects in the spine maturation process. Moreover, we show that TSPAN5 interacts with the postsynaptic adhesion molecule neuroligin-1, promoting its correct surface clustering. We propose that membrane compartmentalization by tetraspanins represents an additional mechanism for regulating excitatory synapses. • TSPAN5 is expressed in pyramidal neurons and localizes mainly to dendritic spines • TSPAN5 interacts with neuroligin-1 and promotes its clustering • TSPAN5-neuroligin-1 complex is fundamental for dendritic spine maturation Moretto et al. demonstrate that TSPAN5 controls the maturation of dendritic spines by promoting the clustering of neuroligin-1. These findings provide proof of principle that compartmentalization of transmembrane proteins through tetraspanins can represent an additional level of regulation of synapse formation and function. [ABSTRACT FROM AUTHOR]