IDENTIFICATION OF CYTOKERATIN-1 AS A BINDING-PROTEIN AND PRESENTATIONRECEPTOR 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 mol ecular mass kininogen (HK) affinity column that, on aminoterminal sequ encing of tryptic digests, was identified as cytokeratin 1, Multiple a ntibodies directed to cytokeratin 1 reacted with a 54-kDa band on immu noblot of lysates of endothelial cells, On laser scanning: confocal mi croscopy, cytokeratin 1 antigen was found on the surface of endothelia l tells, Cytokeratin 1 antigen also was detected on. endothelial cell membranes by flow cytometry, Moreover, an antipeptide antibody to a se quence unique to cytokeratin 1 also specifically bound to nonpermeabil ized endothelial cells. Biotin-HK specifically bound to cytokeratin on ly in the presence of Zn2+, and cytokeratin blocked biotin-HK binding to endothelial cells, Further, HK and low molecular mass kininogen, bu t not factor XII, blocked biotin-HK binding to cytokeratin, and pep ti des of each cell binding region of HK on domains 3,4, and 5 blocked bi otin-HK binding to cytokeratin. gC1qR and soluble urokinase-like plasm inogen activator receptor also inhibited biotin-HK binding to cytokera tin, These investigations identify a new function for cytokeratin 1 as a kininogen binding protein, Cytokeratins, members of the family of i ntermediate filament proteins, may represent a new class of receptors.