Claudin-2 knockdown decreases matrix metalloproteinase-9 activity and cell migration via suppression of nuclear Sp1 in A549 cells

AimsClaudin expression is altered in lung cancer, but the pathophysiological role of claudin is not well understood. We examined the effect of claudin-2 expression on cell migration using human adenocarcinoma A549 cells.Main methodsThe mRNA level was measured by real time polymerase chain reaction. To knockdown claudin-2 expression, we made the cells expressing doxycycline-inducible claudin-2 shRNA vector. The protein level was examined by Western blotting. Cell migration was measured by wound-healing assay. The enzymatic activity of MMP-9 was assessed by gelatin zymography.Key findingsIn A549 cells, claudin-2 expression was higher than in normal lung tissue. Claudin-2 knockdown did not affect the expression of other junctional proteins including claudin-1, occludin and E-cadherin. Claudin-2 knockdown decreased cell migration concomitant with a decrease in the mRNA level and enzymatic activity of MMP-9. The expression level of Sp1 in the nuclei was decreased by claudin-2 knockdown. In contrast, the expression levels of c-Fos, c-Jun and NF-kB p65 in the nuclei were not changed by claudin-2 knockdown. The knockdown of Sp1 expression by siRNA decreased cell migration, and the mRNA expression, enzymatic activity, and promoter activity of MMP-9.SignificanceClaudin-2 may increase the mRNA level and enzymatic activity of MMP-9 mediated by the elevation of nuclear distribution of Sp1, resulting in the up-regulation of A549 cell migration.