Protease nexin-1 complexes and inhibits T cell serine proteinase-1

Abstract

The T cell serine proteinase-1 (TSP-1) which most probably is involved in cell killing by cytotoxic T cells is inhibited by protease nexin-1 (PN-1), an extravascular serine protease inhibitor. The inhibition is irreversible and correlates with formation of SDS-stable complexes between the two proteins. Two distinct species of complexes (91 and 122 kDa) are observed upon SDS-PAGE analysis of the reacted proteins, indicating that PN-1 is capable of complexing and inhibiting both subunits of the homodimeric TSP-1 molecule. Heparin (2 ug/ml) increases the association rate constant from 4.2×10 4 M −1 sec −1 to 4.8×10 5 M −1 sec −1. These observations suggest that PN-1 may function as a major extravascular inhibitor of TSP-1 released from cytotoxic T lymphocytes.