Mitogen-Activated Protein Kinase Signaling Regulates Proteoglycan Composition of Mast Cell Secretory Granules

Abstract

Mast cells (MCs) are characterized by an abundance of lysosome-like secretory granules filled with immunomodulatory compounds including histamine, cytokines, lysosomal hydrolases, MC-restricted proteases, and serglycin proteoglycans. The latter are essential for promoting the storage of other granule compounds and are built up of the serglycin core protein to which highly sulfated and thereby negatively charged glycosaminoglycan (GAG) side chains of heparin or chondroitin sulfate type are attached. In the search for mechanisms operating in regulating MC granule homeostasis, we here investigated the role of mitogen-activated protein kinase (MAPK) signaling. We show that inhibition of MEK1/2 (a MAPK kinase) leads to increased metachromatic staining of MC granules, indicative of increased proteoglycan content. Indeed, MEK1/2 inhibition caused a profound increase in the expression of the gene coding for the serglycin core protein and of genes coding for various enzymes involved in the biosynthesis/sulfation of the GAGs attached to the serglycin core protein. This was accompanied by corresponding increases in the levels of the respective GAGs. Deletion of the serglycin core protein abrogated the induction of enzymes operative in proteoglycan synthesis, indicating that availability of the serglycin proteoglycan core protein has a regulatory function impacting on the expression of the various serglycin-modifying enzymes. MEK1/2 inhibition also caused a substantial increase in the expression of granule-localized, proteoglycan-binding proteases. Altogether, this study identifies a novel role for MAPK signaling in regulating the content of secretory granules in MCs.

CREB Is Activated by the SCF/KIT Axis in a Partially ERK-Dependent Manner and Orchestrates Survival and the Induction of Immediate Early Genes in Human Skin Mast Cells

“…In fact, ERK can also phosphorylate and thereby activate transcriptional repressors [ 54 ]. In MCs, ERK has also been described as a negative regulator of lineage attributes such as secretory granule constituents [ 69 ].…”

Authentic and Ectopically Expressed MRGPRX2 Elicit Similar Mechanisms to Stimulate Degranulation of Mast Cells

“…The first cluster, which comprises ERK1/2 MAP kinase signaling, is also shared with the IgE pathway [ 48 , 51 , 54 ], implying that ERK1 and 2 regulate a central step in the exocytic process that is independent of the stimulus type. Given the short period of incubation with the MEK inhibitor U0126 and the fast kinetics of degranulation, the contribution of ERK1/2 to the secretory process is unlikely to involve transcriptional functions, such as in the case of newly synthesized mediators by activated MCs [ 48 , 51 , 54 ], nor is it likely to be due to interference with the biogenesis of the SGs that was recently shown to require ERK1/2 signaling [ 55 ]. Thus, the precise mechanism by which ERK1/2 may regulate exocytosis is presently unknown.…”

3,4,5‑Trihydroxycinnamic acid suppresses phorbol‑12‑myristate‑13‑acetate and A23187‑induced mast cell activation in RBL‑2H3 cells

“…THC significantly suppressed PMA/A23187-induced MAPKs phosphorylation. Signaling pathways of MAPKs have been extensively demonstrated to be involved in the degranulation of activated mast cells (30,31). In the present study, the phosphorylation of MAPKs was examined in the presence of PMA/A23187 to determine the effect of mast cell activation on MAPK phosphorylation and then the role of THC was measured on the PMA/A23187-induced MAPKs phosphorylation in RBL-2H3 cells.…”

“…MAPK cascade is a crucial signaling pathway involved in various immune response (37,38). Previous reports have demonstrated that the production of inflammatory cytokines and mediators during the mast cell activation is associated with MAPKs signaling (7,30,31). The addition of PMA and A21387 to mast cells results in the phosphorylation of MAPK cascade including p38, ERK1/2, and JNK pathways and subsequent expression of cytokines (39,40).…”