Loss of histochemical identity in mast cells lacking carboxypeptidase A.
Mast cell carboxypeptidase A (Mc-cpa) is a highly conserved secretory granule protease. The onset of expression in mast cell progenitors and lineage specificity suggest an important role for Mc-cpa in mast cells. To address the function of Mc-cpa, we generated Mc-cpa-null mice. Mc-cpa-/- mast cells lacked carboxypeptidase activity, revealing that Mc-cpa is a nonredundant enzyme. While Mc-cpa-/- peritoneal mast cells were ultrastructurally normal and synthesized normal amounts of heparin, they displayed striking histochemical and biochemical hallmarks of immature mast cells. Wild-type peritoneal mast cells had a mature phenotype characterized by differential histochemical staining with proteoglycan-reactive dyes (cells do not stain with alcian blue but stain with safranin and with berberine) and a high side scatter to forward scatter ratio by flow cytometry and were detergent resistant. In contrast, Mc-cpa-/- peritoneal mast cells, like immature bone marrow-derived cultured mast cells, stained with alcian blue normally or weakly and either did not stain with safranin and berberine or stained weakly, had a low side scatter to forward scatter ratio, and were detergent sensitive. This phenotype was partially ameliorated with age. Thus, histochemistry and flow cytometry, commonly used to measure mast cell maturation, deviated from morphology in Mc-cpa-/- mice. The Mc-cpa-/- mast cell phenotype was not associated with defects in degranulation in vitro or passive cutaneous anaphylaxis in vivo. Collectively, Mc-cpa plays a crucial role for the generation of phenotypically mature mast cells.
Department of Immunology, University of Ulm, D-89070 Ulm, Germany.
Thorsten B
TB
Feyerabend
Heinz
H
Hausser
Annette
A
Tietz
Carmen
C
Blum
Lars
L
Hellman
Anita H
AH
Straus
Hélio K
HK
Takahashi
Ellen S
ES
Morgan
Ann M
AM
Dvorak
Hans Jörg
HJ
Fehling
Hans-Reimer
HR
Rodewald
D000818:Animals; D000906:Antibodies / Q000276:immunology; D001599:Berberine / Q000494:pharmacology; D043422:Carboxypeptidases A / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D006493:Heparin / Q000276:immunology / Q000378:metabolism; D006651:Histocytochemistry; D008407:Mast Cells / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure*; D051379:Mice; D008817:Mice, Mutant Strains; D018945:Monocyte Chemoattractant Proteins / Q000378:metabolism; D010641:Phenotype; D011509:Proteoglycans / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism; D053802:Tryptases
D000906:Antibodies; C099677:CCL13 protein, human; D018945:Monocyte Chemoattractant Proteins; D011509:Proteoglycans; C509190:Tpsb2 protein, mouse; D001599:Berberine; D006493:Heparin; D043422:Carboxypeptidases A; C503326:Cpa3 protein, mouse; D012697:Serine Endopeptidases; C509222:Tpsab1 protein, mouse; D053802:Tryptases