Impairment of NF-kappaB activation and modulation of gene expression by calpastatin

To address the involvement of the calpain systemin both basal and silica-induced nuclear factor (NF)-B activation,several human bronchial epithelial cell lines were established in which an intracellular inhibitor of calpain, calpastatin, was stably expressed. Reduced basal and silica-induced inhibitor (IB)degradation and NF-B activation were observed in cells stablyoverexpressing calpastatin. In addition, the cells in which calpain wasconstitutively inhibited by the overexpression of calpastatin exhibiteda notable morphological change. Whereas empty vector-transfected cellsdisplayed a morphology indistinguishable from that of parental cells,cells overexpressing calpastatin exhibited a mosaic morphologicalchange with reduced formation of lamella 30 min after the cells were seeded. Genefilter microarray experiments, in which 3,965 human genescan be evaluated for their expression at the same time, showed thatcalpastatin downregulated genes encoding several membrane-associated proteins or nuclear proteins and upregulated genes of collagen 2,DAZ, and mitochondrial capsule selenoprotein. These results suggestthat, in addition to their proteolytic activities on cytoskeletal proteins and other cellular regulatory proteins, calpain-calpastatin systems can also affect the expression levels of genes encoding structural or regulatory proteins.