Chapter 3 New Insights on Mast Cell Activation via the High Affinity Receptor for IgE

Wiskott-Aldrich syndrome protein–interacting protein (WIP) stabilizes actin filaments and is important for immunoreceptor-mediated signal transduction leading to actin cytoskeleton rearrangement in T and B cells. Here we report a role for WIP in signaling pathways downstream of the high affinity receptor for immunoglobulin (Ig)E (FcϵRI) in mast cells. WIP-deficient bone marrow–derived mast cells (BMMCs) were impaired in their capacity to degranulate and secrete interleukin 6 after FcϵRI ligation. Calcium mobilization, phosphorylation of Syk, phospholipase C-g2, and c-Jun NH2-terminal kinase were markedly decreased in WIP-deficient BMMCs. WIP was found to associate with Syk after FcϵRI ligation and to inhibit Syk degradation as evidenced by markedly diminished Syk levels in WIP-deficient BMMCs. WIP-deficient BMMCs exhibited no apparent defect in their subcortical actin network and were normal in their ability to form protrusions when exposed to an IgE-coated surface. However, the kinetics of actin changes and the cell shape changes that follow FcϵRI signaling were altered in WIP-deficient BMMCs. These results suggest that WIP regulates FcϵRI-mediated mast cell activation by regulating Syk levels and actin cytoskeleton rearrangement.

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New Regulatory Roles of Galectin-3 in High-Affinity IgE Receptor Signaling

Molecular and Cellular Biology ◽

10.1128/mcb.00064-16 ◽

2016 ◽

Vol 36 (9) ◽

pp. 1366-1382 ◽

Cited By ~ 11

Author(s):

Monika Bambouskova ◽

Iva Polakovicova ◽

Ivana Halova ◽

Gautam Goel ◽

Lubica Draberova ◽

...

Keyword(s):

Mast Cell ◽

Mast Cells ◽

Cell Activation ◽

Mast Cell Degranulation ◽

Negative Regulator ◽

Mast Cell Activation ◽

High Affinity ◽

Galectin 3 ◽

High Affinity Receptor ◽

High Affinity Ige Receptor

Aggregation of the high-affinity receptor for IgE (FcεRI) in mast cells initiates activation events that lead to degranulation and release of inflammatory mediators. To better understand the signaling pathways and genes involved in mast cell activation, we developed a high-throughput mast cell degranulation assay suitable for RNA interference experiments using lentivirus-based short hairpin RNA (shRNA) delivery. We tested 432 shRNAs specific for 144 selected genes for effects on FcεRI-mediated mast cell degranulation and identified 15 potential regulators. In further studies, we focused on galectin-3 (Gal3), identified in this study as a negative regulator of mast cell degranulation. FcεRI-activated cells with Gal3 knockdown exhibited upregulated tyrosine phosphorylation of spleen tyrosine kinase and several other signal transduction molecules and enhanced calcium response. We show that Gal3 promotes internalization of IgE-FcεRI complexes; this may be related to our finding that Gal3 is a positive regulator of FcεRI ubiquitination. Furthermore, we found that Gal3 facilitates mast cell adhesion and motility on fibronectin but negatively regulates antigen-induced chemotaxis. The combined data indicate that Gal3 is involved in both positive and negative regulation of FcεRI-mediated signaling events in mast cells.

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