Identification of cytokeratin 1 as a binding protein and presentation receptor for kininogens on endothelial cells

A kininogen binding protein(s), a putative receptor, was identified on endothelial cells, A 54-kDa protein was isolated by a biotin-high molecular mass kininogen (HK) affinity column that, on aminoterminal sequencing of tryptic digests, was identified as cytokeratin 1, Multiple antibodies directed to cytokeratin 1 reacted with a 54-kDa band on immunoblot of lysates of endothelial cells, On laser scanning: confocal microscopy, cytokeratin 1 antigen was found on the surface of endothelial tells, Cytokeratin 1 antigen also was detected on. endothelial cell membranes by flow cytometry, Moreover, an antipeptide antibody to a sequence unique to cytokeratin 1 also specifically bound to nonpermeabilized endothelial cells. Biotin-HK specifically bound to cytokeratin only in the presence of Zn2+, and cytokeratin blocked biotin-HK binding to endothelial cells, Further, HK and low molecular mass kininogen, but not factor XII, blocked biotin-HK binding to cytokeratin, and pep tides of each cell binding region of HK on domains 3,4, and 5 blocked biotin-HK binding to cytokeratin. gC1qR and soluble urokinase-like plasminogen activator receptor also inhibited biotin-HK binding to cytokeratin, These investigations identify a new function for cytokeratin 1 as a kininogen binding protein, Cytokeratins, members of the family of intermediate filament proteins, may represent a new class of receptors.