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Protease nexin-1 complexes and inhibits T cell serine proteinase-1
D Gurwitz1, M M Simon, U Fruth
1Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine 92717.
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 micrograms/ml) increases the association rate constant from 4.2 x 10(4) M-1 sec-1 to 4.8 x 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.
Insights
Protease nexin-1 (PN-1) irreversibly inhibits T cell serine proteinase-1 (TSP-1), a key player in cytotoxic T cell killing. PN-1 effectively complexes and inhibits both subunits of the TSP-1 homodimer.
Area of Science:
- Biochemistry
- Immunology
Background:
- T cell serine proteinase-1 (TSP-1) is implicated in cytotoxic T cell-mediated killing.
- Protease nexin-1 (PN-1) is an extravascular serine protease inhibitor.
Purpose of the Study:
- To investigate the inhibitory mechanism of PN-1 on TSP-1.
- To elucidate the interaction between PN-1 and TSP-1.
Main Methods:
- SDS-PAGE analysis to detect protein complexes.
- Kinetic analysis of the association rate constant.
Main Results:
- PN-1 forms irreversible, SDS-stable complexes with TSP-1.
- Two distinct complex species (91 and 122 kDa) indicate PN-1 inhibits both TSP-1 subunits.
- Heparin significantly enhances the association rate constant between PN-1 and TSP-1.
Conclusions:
- PN-1 is a potent inhibitor of TSP-1.
- PN-1 likely functions as a primary extravascular regulator of TSP-1 released by cytotoxic T lymphocytes.