NEUTROPHILS IN BEIGE MICE SECRETE NORMAL AMOUNTS OF CATHEPSIN-G AND A46 KDA LATENT FORM OF ELASTASE THAT CAN BE ACTIVATED EXTRACELLULARLY BY PROTEOLYTIC ACTIVITY
E. Cavarra et al., NEUTROPHILS IN BEIGE MICE SECRETE NORMAL AMOUNTS OF CATHEPSIN-G AND A46 KDA LATENT FORM OF ELASTASE THAT CAN BE ACTIVATED EXTRACELLULARLY BY PROTEOLYTIC ACTIVITY, Biological chemistry, 378(5), 1997, pp. 417-423
Among other phenotypic defects, the beige mouse is susceptible to infe
ction and has large neutrophil granules that apparently secrete a decr
eased amount of elastolytic activity. We have shown using in vitro met
hods that cytosolic inhibitors in beige neutrophils are normal, Althou
gh cathepsin G is tightly bound to lysosomal membranes, normal amounts
of activity are released in response to degranulating agents. Decreas
ed elastolytic activity is secreted by beige neutrophils because elast
ase is present in the granules as a 46 kDa proenzyme, which can be act
ivated extracellularly by a protease-dependent mechanism. The current
experiments were undertaken to explore the in vivo functions of neutro
phils from C57 BI/6J (bg/bg) beige mice using the model of casein-indu
ced acute peritonitis; normal C57 BI/6J (+/+) mice served as controls.
The kinetics of neutrophil accumulation in the peritoneum were normal
, suggesting normal neutrophil migration. Cathepsin G activity in the
cell-free supernatant of peritoneal lavage fluid was normal; elastolyt
ic activity was initially very low but increased to about twice baseli
ne level after 4 h at 25 degrees C and to about 20-fold at 36 h. The a
ppearance of this activity was inhibited to varying degree (54 to 83%)
by different protease inhibitors (pepstatin, antipain, aprotinin, leu
peptin and chymostatin), We conclude that the decreased amount of elas
tolytic activity secreted by beige neutrophils into an inflammatory ex
udate is due to a genetic defect that results in production of a 46 kD
a proelastase rather than the normal 29 kDa active elastase; the proel
astase can be spontaneously activated by a protease-dependent mechanis
m. In light of these data, the use of the beige mouse as a model for t
he Chediak-Higashi syndrome, and as a model in which neutrophils do no
t produce elastase, must be reconsidered.