Differential targeting of secretory lysosomes and recycling endosomes in mast cells revealed by patterned antigen arrays

Abstract

Polarized response towards a contact interface is a common theme in intercellular signaling. To visualize spatial regulation of stimulated secretion within a contact region, we exposed IgE-sensitized rat basophilic leukemia (RBL) mast cells to a surface that was patterned on the microm scale with hapten-containing lipid bilayers to activate cell surface IgE-receptor complexes. We find that, within 10 minutes of stimulation, fusion of individual secretory lysosomes is targeted towards the cell-substrate interface, but is spatially segregated from the patterned bilayers and receptor signaling complexes. By contrast, stimulated outward trafficking of recycling endosomes is preferentially targeted towards the patterned bilayers. High spatial resolution of both antigen presentation in these arrays and detection of exocytotic events provides direct evidence for the heterogeneity of polarized responses.

Mast cells form antibody-dependent degranulatory synapse for dedicated secretion and defence

“…The dynamic picture of the degranulation process also allows to link the ongoing polarized exocytosis to FcR triggering. Our data extend data reported by Wu et al who focused on localized endosomal recycling and not on mast cell degranulation 30 . In agreement with this and other reports [30][31][32] , we show that FcR and the associated signalling component LAT cluster in the proximity of the budding granules.…”

“…Our data extend data reported by Wu et al who focused on localized endosomal recycling and not on mast cell degranulation 30 . In agreement with this and other reports [30][31][32] , we show that FcR and the associated signalling component LAT cluster in the proximity of the budding granules. These results, together with the observation of a localized clearance of actin cytoskeleton at the degranulatory synapse, provide a mechanistic link between localized signalling and polarized secretion.…”

“…Carroll-Portillo et al showed that FcR clusters are detectable at the mast cell/lipid bilayer contact area 1 min after stimulation and then, they coalesce leading to the formation of a mast cell synapse 32 . Using patterned lipid bilayers, Wu et al reported that secretion is directed towards the substrate where the stimuli are located, but do not strictly co-localize with the signalling clusters 30 .…”

“…Studies using supported lipid bilayers showed that localized FceRI stimulation leads to receptor clustering and signalling and to granule exocytosis [29][30][31][32] . Although surrogate stimulatory surfaces are instrumental to study the dynamics of receptors and associated signalling components, they do not mimic the complex molecular interactions occurring at the cell-cell contact site.…”

Decoding the Regulation of Mast Cell Exocytosis by Networks of Rab GTPases

“…In accordance, Liu et al (56) demonstrated that migrating RBL cells do not secrete and when they secrete they stiffen. Along this line of thought, RBL cells display both polarized and receptor-stimulated endocytic recycling (57,58), and we show in this paper that they also express Rab13, Rab17, Rab20, and Rab25, which are all implicated in polarized transport in epithelial cells. Alternatively, the ERC may mediate acquisition of exocytosis competence by the SGs in analogy to its role in exocytosis of CTL granules (59).…”