title: Granzyme H is a novel protease expressed by human mast cells.
abstract: BACKGROUND
  Many of the functions attributed to mast cells depend on the various pro-inflammatory mediators that are secreted upon mast cell activation. These include a panel of mast cell-specific proteases. In addition, recent studies have indicated that murine mast cells also express granzyme D, a protease previously thought to be confined to cytotoxic lymphocytes. Here, we address the human relevance of the latter findings by investigating whether human mast cells express granzyme H, the granzyme that may represent the functional counterpart to murine granzyme D.
  
  
  METHODS
  Cord blood-derived mast cells, LAD2 cells and skin mast cells in situ were evaluated for their expression of granzymes using quantitative PCR, Western blot analysis and immunostaining. Mast cells were activated by either calcium ionophore stimulation or IgE receptor cross-linking.
  
  
  RESULTS
  Cord blood-derived mast cells and LAD2 cells were shown to express granzyme H and B mRNA, while granzyme A, K and M expression was undetectable. Mast cell activation by either calcium ionophore or IgE receptor cross-linking caused down-regulated expression of granzyme H. In contrast, granzyme B expression was up-regulated by the same stimuli. Granzyme H expression was also confirmed at the protein level, as shown by both Western blot analysis and confocal microscopy. Further, we show that granzyme H is expressed by human skin mast cells in situ.
  
  
  CONCLUSIONS
  The present findings implicate granzyme H as a novel protease expressed by human mast cells and support earlier findings obtained in natural killer cells suggesting that granzymes B and H are reciprocally regulated.
authors.affiliation: Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Elin
authors.initials: E
authors.lastname: Rönnberg
authors.forename: Gabriela
authors.initials: G
authors.lastname: Calounova
authors.forename: Vivien R
authors.initials: VR
authors.lastname: Sutton
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Trapani
authors.forename: Ola
authors.initials: O
authors.lastname: Rollman
authors.forename: Eva
authors.initials: E
authors.lastname: Hagforsen
authors.forename: Gunnar
authors.initials: G
authors.lastname: Pejler
mesh_terms: D002460:Cell Line; D053804:Granzymes / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008407:Mast Cells / Q000201:enzymology*; D018613:Microscopy, Confocal; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D012333:RNA, Messenger; C069434:GZMH protein, human; D053804:Granzymes