Monoclonal antibodies to protease nexin 1 that differentially block its inhibition of target proteases.
Protease nexin 1 (PN-1) is a protease inhibitor secreted by cultured fibroblasts that forms complexes with certain serine proteases; the complexes bind back to the cells and are internalized and degraded. In the present studies, a panel of PN-1 monoclonal antibodies (mAbs) was isolated; none showed detectable cross-reactivity with four related plasma protease inhibitors. Four purified mAbs (mAbp1, mAbp6, mAbp9, and mAbp18) were tested for their ability to block the formation of complexes between PN-1 and target proteases. mAbp1, as well as a rabbit polyclonal anti-PN-1 IgG preparation, did not block formation of 125I-thrombin-PN-1 complexes. mAbp6, mAbp9, and mAbp18 blocked the formation of 125I-thrombin-PN-1 and 125I-urokinase-PN-1 complexes at stoichiometric concentrations of mAb and PN-1. Studies on their ability to block formation of 125I-trypsin-PN-1 complexes showed that mAbp18 also blocked this reaction at stoichiometric concentrations with PN-1 whereas mAbp6 and mAbp9 blocked less effectively. Thus, mAbp18 appears to bind at or close to the reactive center of PN-1. The blocking mAbs should be useful in studies to probe physiological functions of PN-1.
Wagner
S L
SL
Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine 92717.
Van Nostrand
W E
WE
Lau
A L
AL
Cunningham
D D
DD
D016564:Amyloid beta-Protein Precursor; D000818:Animals; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D002352:Carrier Proteins / Q000276:immunology* / Q000494:pharmacology; D003429:Cross Reactions; D005260:Female; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D011480:Protease Inhibitors / Q000097:blood / Q000276:immunology*; D058255:Protease Nexins; D011956:Receptors, Cell Surface; D013917:Thrombin / Q000378:metabolism*
D016564:Amyloid beta-Protein Precursor; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D002352:Carrier Proteins; D011480:Protease Inhibitors; D058255:Protease Nexins; D011956:Receptors, Cell Surface; D013917:Thrombin