Mammalian diaphanous-related formin 1 (mDia1) coordinates mast cell migration and secretion through its actin-nucleating activity

Abstract

Background: Actin remodeling is a key regulator of mast cell (MC) migration and secretion. However, the precise mechanism underlying the coordination of these processes has remained obscure. Objective: We sought to characterize the actin rearrangements that occur during MC secretion or chemotactic migration and identify the underlying mechanism of their coordination. Methods: Using high-resolution microscopy, we analyzed the dynamics of actin rearrangements in MCs triggered to migration by IL-8 or prostaglandin E 2 or to FcεRI-stimulated secretion. Results: We show that a major feature of the actin skeleton in MCs stimulated to migration is the buildup of pericentral actin clusters that prevent cell flattening and converge the secretory granules (SGs) in the cell center. This migratory phenotype is replaced on encounter of an IgE cross-linking antigen that stimulates secretion through a secretory phenotype characterized by cell flattening, reduction of actin mesh density, ruffling of cortical actin, and mobilization of SGs. Furthermore, we show that knockdown of mammalian diaphanous-related formin 1 (mDia1) inhibits chemotactic migration and its typical actin rearrangements, whereas expression of an active mDia1 mutant recapitulates the migratory actin phenotype and enhances cell migration while inhibiting FcεRI-triggered secretion. However, mice deficient in mDia1 appear to have normal numbers of MCs in various organs at baseline. Conclusion: Our results demonstrate a unique role of actin rearrangements in clustering the SGs and inhibiting their

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

“…β-hexosaminidase activity was determined as previously described [ 26 ]. Briefly, 20 μL aliquots of supernatants and cell lysates derived from cells triggered as indicated were incubated for 90 min, at 37 °C, with 50 μL substrate solution consisting of 1.3 mg/mL p-nitrophenyl- N -acetyl-β- D -glucosaminide in 0.1 M citrate (pH 4.5).…”

The Ingenious Mast Cell: Contemporary insights into mast cell behavior and function

“…Thus, it was proposed that chemokines may either elicit distinct signals in MCs, as opposed to basophils, or that MC SGs are linked to the cell cytoskeleton differently from the basophil granules 77 . Marked differences observed between the actin skeleton in migrating versus secreting MCs support the latter possibility 80 . Analysis of actin rearrangements following chemokine stimulation of MCs revealed an accumulation of pericentral actin clusters that prevent cell flattening and converge the SGs in the cell center 80 .…”

“…Marked differences observed between the actin skeleton in migrating versus secreting MCs support the latter possibility 80 . Analysis of actin rearrangements following chemokine stimulation of MCs revealed an accumulation of pericentral actin clusters that prevent cell flattening and converge the SGs in the cell center 80 . By contrast, reduction in the actin mesh density characterizes the secretory actin phenotype.…”

Actin and Myosin in Non-Neuronal Exocytosis

“…Actin depolymerization with cytochalasin E resulted in more fusion events in stimulated endothelial cells, which suggested an inhibitory role of cortical actin [43]. Similarly, actin depolymerization with latrunculin B [44] or by knock-down of formin mDia1 [45] resulted in increased secretion in mast cells. On the other hand, stabilization of actin filaments with jasplakinolide inhibited exocytosis in natural killer (NK) cells [46].…”