Claudin-4 localization in normal and tumor cells
Claudins are key integral proteins of the tight junction and increasing evidence supports a role for these proteins in non-barrier forming activities. To elucidate a potential function for claudins outside of their traditional role in tight junctions, subcellular localization of claudin-4 was determined in normal mammary epithelial cells as well as breast and ovarian cancer cell lines and the effects of a claudin mimic peptide on cell motility determined. Immunofluorescence revealed that claudin-4 was localized along cellular projections. Using a fluorescent peptide that mimics a conserved sequence in the second extracellular loop of a set of claudin subtypes (that includes claudin-4), exposure of this loop to the extracellular environment was confirmed in non-polarized cells. This peptide inhibited cell motility when normal mammary epithelial cells as well as breast and ovarian tumor cells were subjected to a wound healing assay. Knockdown of claudin-4 also inhibited cell motility and the mimic peptide had no effect on motility in the claudin-4 knockdown cells. Representative confocal microscopy image of subconfluent primary mammary epithelial cells with antibodies directed to claudin-4 (red), ZO-1 (green) and stained with DAPI (blue). Yellow color of the image indicates overlay of the red claudin and the green ZO-1 immunofluorescence.
Taken from: Heidi Wilson et al., 2013, BMC Cell Biology [View article]