Impairment of NF-kappa B activation and modulation of gene expression by calpastatin

To address the involvement of the calpain system in both basal and silica-i nduced nuclear factor (NF)-kappa B activation, several human bronchial epit helial cell lines were established in which an intracellular inhibitor of c alpain, calpastatin, was stably expressed. Reduced basal and silica-induced inhibitor (I kappa B alpha) degradation and NF-kappa B activation were obs erved in cells stably overexpressing calpastatin. In addition, the cells in which calpain was constitutively inhibited by the overexpression of calpas tatin exhibited a notable morphological change. Whereas empty vector-transf ected cells displayed a morphology indistinguishable from that of parental cells, cells overexpressing calpastatin exhibited a mosaic morphological ch ange with reduced formation of lamella 30 min after the cells were seeded. Gene-filter microarray experiments, in which 3,965 human genes can be evalu ated for their expression at the same time, showed that calpastatin downreg ulated genes encoding several membrane-associated proteins or nuclear prote ins and upregulated genes of collagen alpha 2, DAZ, and mitochondrial capsu le selenoprotein. These results suggest that, in addition to their proteoly tic activities on cytoskeletal proteins and other cellular regulatory prote ins, calpain-calpastatin systems can also affect the expression levels of g enes encoding structural or regulatory proteins.