Mast Cell β-Tryptase Is Enzymatically Stabilized by DNA

Abstract

Tryptase is a tetrameric serine protease located within the secretory granules of mast cells. In the secretory granules, tryptase is stored in complex with negatively charged heparin proteoglycans and it is known that heparin is essential for stabilizing the enzymatic activity of tryptase. However, recent findings suggest that enzymatically active tryptase also can be found in the nucleus of murine mast cells, but it is not known how the enzmatic activity of tryptase is maintained in the nuclear milieu. Here we hypothesized that tryptase, as well as being stabilized by heparin, can be stabilized by DNA, the rationale being that the anionic charge of DNA could potentially substitute for that of heparin to execute this function. Indeed, we showed that double-stranded DNA preserved the enzymatic activity of human β-tryptase with a similar efficiency as heparin. In contrast, single-stranded DNA did not have this capacity. We also demonstrated that DNA fragments down to 400 base pairs have tryptase-stabilizing effects equal to that of intact DNA. Further, we showed that DNA-stabilized tryptase was more efficient in degrading nuclear core histones than heparin-stabilized enzyme. Finally, we demonstrated that tryptase, similar to its nuclear localization in murine mast cells, is found within the nucleus of primary human skin mast cells. Altogether, these finding reveal a hitherto unknown mechanism for the stabilization of mast cell tryptase, and these findings can have an important impact on our understanding of how tryptase regulates nuclear events.

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

“…This implies that tryptase may have an impact in the nuclear compartment even in viable cells. In line with this, we found here that tryptase, in addition to its location within secretory granules, also is found within the nuclear compartment of the human mast cell leukemia cells, and there is also previous evidence that tryptase can be found in the nucleus of non-transformed mast cells ( 36 , 37 ). Hence, tryptase can impact on core histones not only during cell death, when large amounts of tryptase are released from granules, but also at steady state.…”

Expression of CD38 in Mast Cells: Cytological and Histotopographic Features

“…In this case, contact cells can capture exosomes and induce their cytolysis with the participation of specific mast cell proteases [26]. In addition to this effect, we should consider the inductive functions of tryptase exerted on the proliferative potencies of the immune contact cell [27,28]. Moreover, the activating effects on the secretion of granzymes and cytokines in NK cells with the acquisition of a cytotoxic phenotype are well-known [41].…”

“…From the point of view of explaining the mechanism of tryptase entry into the nuclei of CD38+ cells, we can assume the regulatory consequences of this phenomenon. In particular, this phenomenon can affect the state of histones and cell proliferation, while tryptase exhibits antiproliferative effects [27,28].…”

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).…”