Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
Department of Medicine, Division of Allergy-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Ill.
J Allergy Clin Immunol. 2019 Oct;144(4):1074-1090. doi: 10.1016/j.jaci.2019.06.028. Epub 2019 Jul 3.
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.
We sought to characterize the actin rearrangements that occur during MC secretion or chemotactic migration and identify the underlying mechanism of their coordination.
Using high-resolution microscopy, we analyzed the dynamics of actin rearrangements in MCs triggered to migration by IL-8 or prostaglandin E or to FcεRI-stimulated secretion.
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.
Our results demonstrate a unique role of actin rearrangements in clustering the SGs and inhibiting their secretion during MC migration. We identify mDia1 as a novel regulator of MC response that coordinates MC chemotaxis and secretion through its actin-nucleating activity.
肌动蛋白重构是调节肥大细胞（MC）迁移和分泌的关键因素。然而，这些过程协调的确切机制仍不清楚。
我们旨在描述 MC 分泌或趋化迁移过程中发生的肌动蛋白重排，并确定其协调的潜在机制。
使用高分辨率显微镜，我们分析了 IL-8 或前列腺素 E 或 FcεRI 刺激分泌刺激下 MC 迁移时肌动蛋白重排的动力学。
我们表明，MC 中迁移刺激的肌动蛋白骨架的一个主要特征是中心周围肌动蛋白簇的积累，这可以防止细胞扁平化并将分泌颗粒（SGs）集中在细胞中心。这种迁移表型在遇到 IgE 交联抗原时会被取代，该抗原通过分泌表型刺激分泌，其特征是细胞扁平化、肌动蛋白网密度降低、皮质肌动蛋白起皱和 SGs 的动员。此外，我们表明，哺乳动物 Dia 相关formin 1（mDia1）的敲低抑制趋化迁移及其典型的肌动蛋白重排，而活性 mDia1 突变体的表达可再现迁移肌动蛋白表型并增强细胞迁移，同时抑制 FcεRI 触发的分泌。然而，mDia1 缺陷小鼠在各种器官中的 MC 数量似乎在基线时正常。
我们的结果表明肌动蛋白重排在 MC 迁移过程中聚集 SGs 并抑制其分泌方面具有独特作用。我们确定 mDia1 是一种新的 MC 反应调节剂，通过其肌动蛋白成核活性协调 MC 趋化性和分泌。
