T. Osterwalder et al., THE AXONALLY SECRETED SERINE PROTEINASE-INHIBITOR, NEUROSERPIN, INHIBITS PLASMINOGEN ACTIVATORS AND PLASMIN BUT NOT THROMBIN, The Journal of biological chemistry, 273(4), 1998, pp. 2312-2321
Neuroserpin is an axonally secreted serine proteinase inhibitor that i
s expressed in neurons during embryogenesis and in the adult nervous s
ystem. To identify target proteinases, we used a eucaryotic expression
system based on the mouse myeloma cell line J558L and vectors includi
ng a promoter from an Ig-kappa-variable region, an Ig-kappa enhancer,
and the exon encoding the Ig-kappa constant region (C kappa) and produ
ced recombinant neuroserpin as a wild-type protein or as a fusion prot
ein with C kappa. We investigated the capability of recombinant neuros
erpin to form SDS-stable complexes with, and to reduce the amidolytic
activity of, a variety of serine proteinases in vitro. Consistent with
its primary structure at the reactive site, neuroserpin exhibited inh
ibitory activity against trypsin-like proteinases. Although neuroserpi
n bound and inactivated plasminogen activators and plasmin, no interac
tion was observed with thrombin. A reactive site mutant of neuroserpin
neither formed complexes with nor inhibited the amidolytic activity o
f any of the tested proteinases. Kinetic analysis of the inhibitory ac
tivity revealed neuroserpin to be a slow binding inhibitor of plasmino
gen activators and plasmin. Thus, we postulate that neuroserpin could
represent a regulatory element of extracellular proteolytic events in
the nervous system mediated by plasminogen activators or plasmin.