Regulation of cell-cell adhesion by the metastasis suppressor tetraspanin CD82/KAI1

Cell junctions are important sites of intercellular adhesion. They preserve the integrity of epithelial tissue and control cell signalling. Deregulation of genes associated with cellular junctions can result in tumour transformation and invasion. Cell junctions consists of desmosomes, tight junctions, gap junctions and adherens junctions. Cellular transformation, invasion and metastasis is brought about by the dysregulation of cell junction components and are therefore crucial for the suppression of metastases. Preliminary experiments in the lab indicated a potential interaction between the metastasis suppressor CD82 a member of the tetraspanin superfamily pf glycoproteins, and desmosomes. By performing Western blotting and semi-quantitative RT-PCR it showed CD82 regulates the expression of desmosomal proteins plakoglobin and desmoglein2, and the distribution of desmoglein2 within the cell. Despite down regulating plakoglobin and desmoglein2 protein levels, CD82 was found to promote cell-cell adhesion. Plakoglobin and CD82 were found to co-localise by immunofluorescence and an interaction was observed by immunoprecipitation. CD82 did not associate with desmoplakin and was not implicated in the trafficking of desmoplakin to the membrane during desmosome assembly. The significance of these finding remain to be determined, but they provide a useful platform for the development of future work