Granzyme B is expressed in mouse mast cells in vivo and in vitro and causes delayed cell death independent of perforin

Abstract

Mast cells respond to pathogens and allergens by secreting a vast array of preformed and newly synthesized mediators, including enzymes, vasoactive amines, lipid mediators, cytokines and chemokines, thereby affecting innate and adaptive immune responses and pathogenesis. Here, we present evidence that skin-, but not lung-associated primary mast cells as well as in vitro-differentiated bone marrow-derived mast cells (BMMC) express granzyme (gzm) B, but not gzmA or perforin (perf). GzmB is associated with cytoplasmic granules of BMMC and secreted after Fce-receptor-mediated activation. BMMC from wild type but not gzmB-deficient mice cause cell death in susceptible adherent target cells, indicating that the perf-independent cytotoxicity of BMMC is executed by gzmB. Furthermore, gzmB induces a disorganization of endothelial cell-cell contacts. The data suggest that activated mast cells contribute, via secreted gzmB, to cell death, increased vascular permeability, leukocyte extravasation and subsequent inflammatory processes in affected tissues.

Death by a Thousand Cuts: Granzyme Pathways of Programmed Cell Death

“…Low levels of perforin mRNA and protein can be detected in one human mast cell line, HMC-1, but not in another (LAD-2) or in primary mast cells derived from cord blood and skin. In mice, only skin-associated mast cells and bone marrow-derived in vitro-differentiated mast cells make GzmB protein, but lung mast cells do not (8). Neither GzmA nor perforin are detected in mouse mast cells.…”

Granzymes in cancer and immunity

“…Granzyme B, but not granzyme A or perforin, is expressed by mast cells and secreted in an active form after ligation of the FceR1 receptor. 17 Basophilsecreted granzyme B promoted the death of adherent target cells and degraded endothelial cell-cell contacts and this has been suggested to mediate increased vascular permeability and extravasation by basophils at points of infection. 17 Furthermore, keratinocytes have been shown to express granzyme B and perforin on irradiation, with UVB-treated keratinocytes acquiring cytotoxicity toward various transformed cell lines in a perforin/granzyme B-dependent manner.…”

“…For example, transformed and activated primary B cells, mast cells, keratinocytes, basophils, macrophages and blood polymorphonuclear neutrophils have all been shown to express granzyme B. 11,[14][15][16][17][18][19][20] Mast cells are especially abundant at the boundary between the internal environment and the outside world, for example, in the skin and lungs, and are thus perfectly situated to coordinate an immune response against a nascent infection. Granzyme B, but not granzyme A or perforin, is expressed by mast cells and secreted in an active form after ligation of the FceR1 receptor.…”

“…Coupled with observations that certain granzymes are expressed and secreted by B cells, mast cells, keratinocytes, basophils, as well as other cell types, in the absence of detectable perforin, this suggests that granzymes may have hitherto unsuspected roles in immunity. 11,[14][15][16][17][18][19][20] Thus, in addition to acting as cell death effector molecules on delivery to target cells, granzymes may also possess activity on release into the extracellular space ( Figure 1). The expanding role for granzymes as possible soluble mediators of inflammation will be discussed later in this review.…”

A quarter century of granzymes

“…90 Furthermore, it has become appreciated that GrB is expressed in the absence of perforin by a variety of non-lymphoid cells. [91][92][93] Thus, there is great speculation that GrB may have extracellular functions that promote extracellular matrix remodeling, cell death, and inflammation. In support of this theory, reports have demonstrated GrB-mediated proteolysis of extracellular matrix proteins.…”