Assembly of high molecular weight kininogen and activation of prekallikrein on cell matrix

Investigations determined if extracellular matrix of endothelial cells (EC) is a platform for HK assembly and PK activation. In buffers containing bov ine serum albumin, biotin-RK binding to ECV304 cells or their matrix requir es greater than or equal to 50 muM added Zn2+. Ortho-phenanthroline or a HK domain 5 peptide blocks HK binding, Binding to umbilical vein EC or matrix , but not ECV304 cells or matrix, is mediated by cytokeratin 1. Biotin-HK b inds to ECV304 cells or matrix with a K-d of 15.8 or 9.0 nM and a B-max of 2.6 X 10(7) or 21.4 X 10(7) sites/cell, respectively. PK activation un ECV3 04 cells or matrix is blocked by antipain or SBTI and corn trypsin inhibito r partially inhibits kallikrein formation. PK activation occurs on ECV304 c ells or matrix prepared without serum or in human factor XII deficient seru m. indicating that the PK activator is not factor XIIa. EC matrix promotes plasminogen activation after the assembly of HK, PK and pro-urokinase. Thes e studies indicate that matrix of various EC has the ability to assemble HK allowing for PK activation and subsequent activities.