Localization of the Novel GAP Family Protein SPAL in Epithelial Cells

抄録

Spa-1-like protein (SPAL) is a newly-identified GTPase-activating protein (GAP) family protein. To verify subcellular localization of SPAL, we performed fluorescence immunohistochemistry in Mardin-Darby canine kidney (MDCK) cells and rat esophagus, pancreas and colon using a cell adhesion-related protein β-catenin as a marker of cell-cell contact sites. SPAL and β -catenin were colocalized along the lateral cell-cell contact sites of MDCK cells, and along the entire cell-cell contact sites of the stratified epithelial cells of the esophagus. In the pancreatic exocrine acinus, SPAL was detected only at the apical end of the β-catenin-immunostained lateral cell-cell contact sites. In the colon, SPAL was localized not only to the apical end of the lateral cell-cell contact sites but also to the apical cell surface. Taken together, SPAL was localized to the entire cell-cell contact sites of the non-polarized cells while in the polarized cells preferentially to the lateral cell-cell contact sites with some variations depending on the cell types. These results suggest that SPAL may be involved in regulation of the epithelial cell-adhesion.