Binding of recombinant human cytokeratin 19 to laminin: a possible role in interaction between intermediate filament derived from epithelial cells and extracellular matrixes.

Cytokeratin 8 (CK8) and cytokeratin 19 (CK19) is a specific cytoskeletal component of simple epithelia, including bronchial epithelial cells. We hypothesized that CK8 or CK19 released from epithelial cells may bind to and cause damage to extracellular matrixes through binding of anti-CK8 or anti-CK19 autoantibodies. In the present study, bindings of recombinant human CK8 and CK19 to laminin (both derived from mouse sarcoma cells and human), collagen, gelatin, and fibronectin were evaluated by a modified enzyme-linked immunosorbent assay (ELISA). In addition, binding of CK19 to laminin was also confirmed by inhibition assay. As a result, CK19 strongly bound to mouse laminin as well as human laminin. Pretreatment with laminin significantly reduced the binding of CK19 to laminin. However, binding of recombinant CK19 to laminin was not demonstrated by Western immunoblot, suggesting that SDS treatment of laminin diminished the binding. These results suggest that released CK19 from epithelial cells may have played a role in the damage of basement membrane by accumulation of an immune complex composed by CK19 and anti-CK19 autoantibody.