The 175 antigen expressed on myeloid and erythroid cells during
differentiation is associated with serine protease activity
D Deane, L Inglis and D Haig
Moredun Research Institute, Edinburgh, Scotland.
Monoclonal antibody 175 recognizes a cell-surface antigen on more than 80%
of nucleated ovine bone marrow cells (BMC). The distribution is unusual, as
the majority of differentiated myeloid and erythroid cells express the
antigen (175 antigen), whereas mast cells, basophils, and the majority of
lymphocytes do not. The level of 175 antigen expression has been shown to
increase as BMC differentiate during hematopoiesis. Previous attempts to
identify the 175 antigen have been unsuccessful. In this study, the 175
antigen was affinity-purified and shown to contain serine protease
activity. Immunoblot analysis following sodium dodecylsulfate
polyacrylamide gel electrophoresis (SDS-PAGE) of bone marrow cell lysates
run under reducing or nonreducing conditions showed two closely adjacent
protein bands (a doublet) of 28 to 30 kD molecular weight. N-linked
deglycosylation showed that the 30-kD band was a glycosylated form of the
28-kD protein. Both protein bands shared the same N-terminal amino acid
sequence over 20 residues, with high homology with serine proteases.
Affinity-purified 175 antigen was proteolytic in substrate gels, the
activity being inhibited by the 175 monoclonal antibody (Mab) and the
serine protease inhibitor phenylmethylsulfonyl fluoride (PMSF), but not by
metallo, thiol, or acid protease-specific inhibitors. The 175 antigen is
therefore part of a growing family of cell-surface proteases associated
with hematopoietic cell differentiation.
Volume 85,
Issue 5,
pp. 1215-1219,
03/01/1995
Copyright © 1995 by The American Society of Hematology
