A 3-DIMENSIONAL COLLAGEN LATTICE ACTIVATES NF-KAPPA-B IN HUMAN FIBROBLASTS - ROLE IN INTEGRIN ALPHA(2) GENE-EXPRESSION AND TISSUE REMODELING

Normal adult human dermal fibroblasts grown in a three-dimensional col lagen lattice increase mRNA level of collagen receptor integrin subuni t alpha(2) (Xu, J., and R.A.F. Clark. 1996, J. Cell Biol. 132:239-249. ) and DNA binding activity of a nuclear transcription factor, NF-kappa B (Xu, J., and R.A.F. Clark. 1997, J. Cell Biol. 136:473-483.). Here we present evidence that the collagen lattice induced the nuclear tran slocation of p50, one member of NF-kappa B family, and the degradation of an NF-kappa B inhibitor protein, I kappa B-alpha. The inhibition o f NF-kappa B activity by SN50, a peptide inhibitor targeted at nuclear translocation of NF-kappa B, significantly reduced the induction of i ntegrin alpha(2) mRNA and protein by the collagen lattice. A region lo cated between -549 and -351 bp in the promoter of integrin alpha(2) ge ne conferred the inducibility by three-dimensional collagen lattice. T he presence of either SN50 or I kappa B-alpha(32,36), a stable mutant of I kappa B-alpha, abrogated this inducibility, indicating that the a ctivation of integrin alpha(2) gene expression was possibly mediated b y NF-kappa B through this region. Although there were three DNA-protei n binding complexes forming in this region that are sensitive to the i nhibition of NF-kappa B nuclear translocation, NF-kappa B was not dire ctly present in the binding complexes. Therefore, an indirect regulato ry mechanism by NF-kappa B in integrin alpha(2) gene expression induce d by three-dimensional collagen lattice is suggested. The involvement of NF-kappa B in reorganization and contraction of three-dimensional c ollagen lattice, a process that requires the presence of abundant inte grin alpha(2) beta(1), was also examined, The inhibition of NF-kappa B activity by SN50 greatly blocked the contraction, suggesting its crit ical role in not only the induction of integrin alpha(2) gene expressi on by three-dimensional collagen lattice, but also alpha(2) beta(1)-me diated tissue-remodeling process.