IDENTIFICATION AND CHARACTERIZATION OF THE CELL-ASSOCIATED BINDING-PROTEIN FOR URINARY TRYPSIN-INHIBITOR

Urinary trypsin inhibitor (UTI) inhibits not only tumor cell invasion but also production of experimental and spontaneous metastasis. Cell-b inding experiments indicated that human choriocarcinoma SMT-cc1 cells have specific binding sites for UTI on their cell surface. [Kobayashi et al., J. Biol. Chem. 269, 1994, 20642-20647]. UTI binding protein (U TIBP) was purified to homogeneity by a combination of UTI-coupled affi nity beads, preparative polyacrylamide gel electrophoresis and reverse phase HPLC. This protein is very similar to a truncated form of human cartilage link protein (LP). LP was identified structurally by its ap parent molecular mass with and without deglycosylation treatment. Immu nologically by the reactivity with anti-UTIBP antibody, and functional ly by its ability to bind the NH2-terminal domain of UTI. UTI and UTIB P are distributed uniformly in the cytoplasm and/or over the cell surf ace of tumor cells and fibroblasts. The level of staining for hyaluron ic acid, UTIBP and UTI is much lower in sections digested with hyaluro nidase. These results suggest that the cell membrane-derived UTI-assoc iated binding protein is the LP of proteoglycan-hyaluronic acid aggreg ates, which interacts with hyaluronic acid. Cell-associated LP may pla y a role in modulating protease activity to the environment close to t umor and fibroblast cell surface. (C) 1998 Elsevier Science B.V.