Tryptase Regulates the Epigenetic Modification of Core Histones in Mast Cell Leukemia Cells

Abstract

Mast cells are immune cells that store large amounts of mast cell-restricted proteases in their secretory granules, including tryptase, chymase and carboxypeptidase A3. In mouse mast cells, it has been shown that tryptase, in addition to its canonical location in secretory granules, can be found in the nuclear compartment where it can impact on core histones. Here we asked whether tryptase can execute core histone processing in human mast cell leukemia cells, and whether tryptase thereby can affect the epigenetic modification of core histones. Our findings reveal that triggering of cell death in HMC-1 mast cell leukemia cells is associated with extensive cleavage of core histone 3 (H3) and more restricted cleavage of H2B. Tryptase inhibition caused a complete blockade of such processing. Our data also show that HMC-1 cell death was associated with a major reduction of several epigenetic histone marks, including H3 lysine-4-mono-methylation (H3K4me1), H3K9me2, H3 serine-10-phosphorylation (H3S10p) and H2B lysine-16-acetylation (H2BK16ac), and that tryptase inhibition reverses the effect of cell death on these epigenetic marks. Further, we show that tryptase is present in the nucleus of both viable and dying mast cell leukemia cells. In line with a role for tryptase in regulating nuclear events, tryptase inhibition caused increased proliferation of the mast cell leukemia cells. Altogether, the present study emphasizes a novel principle for how epigenetic modification of core histones is regulated, and provides novel insight into the biological function of human mast cell tryptase.

Carboxypeptidase A3—A Key Component of the Protease Phenotype of Mast Cells

“…In some cases, the directed secretion of CPA3 towards the nuclear structures of other cells becomes apparent (Figure 4g-l). The study of CPA3 in this aspect seems to be of particular interest after the discovery of the ability of tryptase to have regulatory effects on nuclear histones and thereby influence the proliferative activity of cells [120][121][122]. Moreover, there is clear immunohistochemical evidence of tryptase and CPA3 co-localization in the case of directed secretion of proteases to the nuclei of other cells (Figure 3a).…”

“…Tryptase has recently been shown to have epigenetic effects due to its influence on the state of nuclear histones and DNA stabilization [120][121][122]. The close co-localization of CPA3 with tryptase leads to some interest in the extent to which exopeptidase is involved in these effects (Figure 3a).…”

Sodium butyrate supresses malignant human mast cell proliferation, downregulates expression of KIT and promotes differentiation

“…The other HDACi that were tested, TSA and SAHA, appeared to have the same effect, although only the TSA increase in histamine content was statistically significant. A recent study by Alanazi et al has shown that when HMC-1 are induced to undergo apoptosis by HDACi (LLME, staurosporine, UNC-0,638 and UNC-1999), tryptase is released and cleaves histones 3 and 2B, leading to increased proliferation (67). Viability in the Alanazi et al study was measured using a resazurin-based assay which measures cell metabolic activity similar to the XTT assay used in our analysis.…”

Mast Cell Tryptase and Carboxypeptidase A3 in the Formation of Ovarian Endometrioid Cysts

“…The results of recent studies that have investigated the fundamental significance of tryptase entry into the nuclei of other cells [ 50 ] are supported by our findings, evidencing the potential, significant morphogenetic effects of MCs on the ovarian stroma. In particular, nuclear tryptase can process the core histones in the N-terminal tail, and thereby regulate transcription processes [ 51 , 52 ]. The provided principle of regulating the epigenetic modification of core histones, which ultimately leads to the restriction of cell proliferation, represents a strategically novel understanding of the biological function of human MC tryptase [ 52 ].…”