Fate of two mast cell tryptases in V3 mastocytosis and normal BALB/c mice undergoing passive systemic anaphylaxis: prolonged retention of exocytosed mMCP-6 in connective tissues, and rapid accumulation of enzymatically active mMCP-7 in the blood.
The mouse mast cell protease granule tryptases designated mMCP-6 and mMCP-7 are encoded by highly homologous genes that reside on chromosome 17. Because these proteases are released when mast cells are activated, we sought a basis for distinctive functions by examining their fates in mice undergoing passive systemic anaphylaxis. 10 min-1 h after antigen (Ag) was administered to immunoglobulin (Ig)E-sensitized mice, numerous protease/proteoglycan macromolecular complexes appeared in the extracellular matrix adjacent to most tongue and heart mast cells of normal BALB/c mice and most spleen and liver mast cells of V3 mastocytosis mice. These complexes could be intensively stained by anti-mMCP-6 Ig but not by anti-mMCP-7 Ig. Shortly after Ag challenge of V3 mastocytosis mice, large amounts of properly folded, enzymatically active mMCP-7 were detected in the plasma. This plasma-localized tryptase was approximately 150 kD in its multimeric state and approximately 32 kD in its monomeric state, possessed an NH2 terminus identical to that of mature mMCP-7, and was not covalently bound to any protease inhibitor. Comparative protein modeling and electrostatic calculations disclosed that mMCP-6 contains a prominent Lys/Arg-rich domain on its surface, distant from the active site. The absence of this domain in mMCP-7 provides an explanation for its selective dissociation from the exocytosed macromolecular complex. The retention of exocytosed mMCP-6 in the extracellular matrix around activated tissue mast cells suggests a local action. In contrast, the rapid dissipation of mMCP-7 from granule cores and its inability to be inactivated by circulating protease inhibitors suggests that this tryptase cleaves proteins located at more distal sites.
Ghildyal
N
N
Department of Medicine, Harvard Medical School, Boston, Massachusetts, USA.
Friend
D S
DS
Stevens
R L
RL
Austen
K F
KF
Huang
C
C
Penrose
J F
JF
Sali
A
A
Gurish
M F
MF
D000707:Anaphylaxis / Q000201:enzymology*; D000818:Animals; D053818:Chymases; D004591:Electrophoresis, Polyacrylamide Gel; D005089:Exocytosis; D006863:Hydrogen-Ion Concentration; D018836:Inflammation Mediators / Q000378:metabolism*; D008407:Mast Cells / Q000201:enzymology*; D008415:Mastocytosis / Q000201:enzymology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010449:Peptide Mapping; D017452:Receptors, IgG / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D053802:Tryptases
D018836:Inflammation Mediators; D017452:Receptors, IgG; C509190:Tpsb2 protein, mouse; D012697:Serine Endopeptidases; C083294:chymase 2; D053818:Chymases; C509222:Tpsab1 protein, mouse; D053802:Tryptases