PDZ interaction of the GABA transporter GAT1 with the syntenin-1 in Neuro-2a cells.

The GABA transporter GAT1 regulates brain inhibitory neurotransmission and it is considered a potential therapeutic target for the treatment of wide spectrum of neurological diseases including epilepsy, stroke and autism. Syntenin-1 binds to syntaxin 1A, which is known to regulate the plasma membrane insertion of several neurotransmitter transporters. Previously, a direct interaction of syntenin-1 with the glycine transporter GlyT2 was reported. Here, we show that the GABA transporter GAT1 also directly interacts with syntenin-1, involving both unidentified protein interaction interface and the GAT1 C-terminal PDZ binding motif interacting mainly with syntenin-1 PDZ domain 1. The PDZ interaction was eliminated by the mutation of GAT1 isoleucine 599 and tyrosine 598 located in PDZ positions 0 and -1, respectively. This indicates an unconventional PDZ interaction and possible regulation of the transporter PDZ motif via tyrosine phosphorylation. Whole syntenin-1 protein fused to GST protein and immobilised on glutathione resin coprecipitated intact GAT1 transporter from an extract of GAT1 transfected neuroblastoma N2a cells. This coprecipitation was inhibited by tyrosine phosphatases inhibitor pervanadate. The fluorescence tagged GAT1 and syntenin-1 colocalized upon coexpression in N2a cells. The above results show that syntenin-1 might be, in addition to GlyT2, directly involved in the trafficking of GAT1 transporter.

Potential Therapeutic Applications of MDA-9/Syntenin-NF-κB-RKIP Loop in Human Liver Carcinoma.

BACKGROUND: Overexpression of MDA-9/Syntenin occurs in multiple human cancer cell lines and is associated with higher grade of tumor classification, invasiveness and metastasis. In some cases, its role in cancer biology depends on relationships between MDA-9/Syntenin and NF-κB. OBJECTIVE: This study aims to analyze the presence of a regulation loop like that between MDA-9/Syntenin - NF-κB - RKIP in human liver carcinoma. METHODS: Transient transfection was performed with siRNA anti-MDA-9/Syntenin. Expression of different factors was evaluated by Real time-PCR and Western blotting, while NF-κB activation by TransAM assay. Invasion capacity was analyzed by Matrigel Invasion Assay and the effects of agents on cell viability were examined by MTS assay. RESULTS: We have examined basal expression of MDA-9/Syntenin in three cell lines of human liver carcinoma (HA22T/VGH, Hep3B and HepG2). In all cell lines there was an inverse relationship between MDA-9/Syntenin and RKIP expression levels, and a positive correlation between MDA-9/Syntenin expression and NF-κB activation levels. By silencing with a siRNA anti-MDA-9/Syntenin we observed in all cell lines a very strong increase of RKIP at mRNA level. Interestingly, in all cell lines, inhibition of MDA- 9/Syntenin expression induced NF-κB downregulation and contemporary a reduction in invasion ability MMP-2 dependent. Finally, we showed a good additive effect of MDA- 9/Syntenin siRNA when associated with Curcumin or Doxorubicin on cell growth inhibition. CONCLUSION: Our data confirm the key role of MDA-9/Syntenin in HCC biology. The presence of a regulation loop among MDA-9/Syntenin, NF-κB and RKIP provide new pharmacological approaches.

Panax ginseng increases hypoxia-induced down-regulated cellular response related genes in human neuroblastoma cells, SK-N-MC.

BACKGROUND: Many studies have suggested that hypoxia plays a crucial role in the pathogenesis of various neurological disorders. To determine protective effect of Panax ginseng (PG) on hypoxia (0.1% O(2))-induced cell death in human neuroblastoma cells SK-N-MC, we profiled the gene expression among hypoxia, PG-treated hypoxia and normoxia groups. METHODS: To determine protective effect on hypoxia-induced cytotoxicity of PG, we performed 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. We compared the gene expression profiles among hypoxia, PG-treated hypoxia (100 mug/ml, 6 hours) and normoxia groups using 8K human cDNA microarray analysis. Additionally, in order to identify differentially expressed genes between hypoxia and PG-treated hypoxia groups, hierarchical clustering of genes was also performed. RESULTS: MTT assay showed that PG protected hypoxia-induced cell death. In cDNA microarray analysis, hypoxia remarkably down-regulated IGF-II mRNA-binding protein 3 (IMP-3), integrin alpha 2 (ITGA2), syndecan binding protein (SDCBP), insulin-like growth factor binding protein 3 (IGBP3) and M-phase phosphoprotein 10 (MPHOSPH10), belonging to category of cellular physiologic response (global M<-3.5). In cluster analysis, 1428 genes exhibited differential expression levels between hypoxia and PG-treated hypoxia groups. Of them, the expressions of 11 genes were increased more than two-fold by PG treatment compared to those in hypoxia group. Particularly, of 11 genes, the expression levels of cellular physiologic response related genes such as MPHOSPH10, IMP-3 and SDCBP, which markedly down-regulated by hypoxia, are increased more than four-fold by PG treatment, compared to hypoxia group. CONCLUSION: In summary, hypoxia induced down-regulation of cellular physiologic response related genes in human neuroblastoma cells, SK-N-MC, and PG ameliorated the hypoxia-induced down-regulation of such genes. These results indicate possible usage of PG in hypoxia-induced neuronal injury including ischemia, trauma and degenerative diseases.