Granzyme K Activates Protease-Activated Receptor-1

Dawn M Cooper,Dmitri V Pechkovsky,David J Granville,Darryl A Knight,Tillie L Hackett,Silvano Sozzani

doi:10.1371/journal.pone.0021484

Dawn M Cooper, Dmitri V Pechkovsky + Show 4 more

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https://doi.org/10.1371/journal.pone.0021484

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Journal: PloS one	Publication Date: Jun 30, 2011
Citations: 111	License type: CC BY 4.0

Affiliation: St. Paul's Hospital, University of British Columbia

Abstract

Granzyme K (GrK) is a trypsin-like serine protease that is elevated in patients with sepsis and acute lung inflammation. While GrK was originally believed to function exclusively as a pro-apoptotic protease, recent studies now suggest that GrK may possess other non-cytotoxic functions. In the context of acute lung inflammation, we hypothesized that GrK induces pro-inflammatory cytokine release through the activation of protease-activated receptors. The direct effect of extracellular GrK on PAR activation, intracellular signaling and cytokine was assessed using cultured human lung fibroblasts. Extracellular GrK induced secretion of IL-6, IL-8 and MCP-1 in a dose- and time-dependent manner in lung fibroblasts. Heat-inactivated GrK did not induce cytokine release indicating that protease activity is required. Furthermore, GrK induced activation of both the ERK1/2 and p38 MAP kinase signaling pathways, and significantly increased fibroblast proliferation. Inhibition of ERK1/2 abrogated the GrK-mediated cytokine release. Through the use of PAR-1 and PAR-2 neutralizing antibodies, it was determined that PAR-1 is essential for GrK-induced IL-6, IL-8 and MCP-1 release. In summary, extracellular GrK is capable of activating PAR-1 and inducing fibroblast cytokine secretion and proliferation.

Highlights

IntroductionGranzymes (granule-secreted enzymes) are a family of serine proteases that were once thought to function exclusively in immunemediated target cell death through a perforin-dependent mechanism
Granzymes are a family of serine proteases that were once thought to function exclusively in immunemediated target cell death through a perforin-dependent mechanism
Cell viability and proliferation As extracellular Granzyme A (GrA) and Granzyme B (GrB) have been shown to induce cell detachment, we examined the impact of extracellular Granzyme K (GrK) on cell viability and proliferation in Human fetal lung fibroblasts (HFL)

Summary

Introduction

Granzymes (granule-secreted enzymes) are a family of serine proteases that were once thought to function exclusively in immunemediated target cell death through a perforin-dependent mechanism. There are 5 granzymes that differ in both function and substrate specificity: Granzyme A (GrA; tryptase), Granzyme B (GrB; aspartase), Granzyme H (GrH; chymase), Granzyme K (GrK; tryptase) and Granzyme M (GrM; metase). Despite their initial discovery and prediction to act as both intracellular and extracellular proteases, traditional views have limited granzyme function to the intracellular, perforin-dependent induction of cell death. GrK is found at low levels in the plasma of healthy patients but is markedly elevated in the plasma of patients suffering from viral infections and sepsis [11,15]. Our understanding of the proteolytic regulation of extracellular GrK remains poorly understood, recent studies have identified inter-alpha inhibitor proteins (IAIP) as physiological inhibitors of GrK and have shown that a reduction in plasma IAIP levels and free, unbound GrK correspond to increased disease severity [16,17]

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