What Is the Role of Giant Endosomal Sorting Complexes Required for Transport (ESCRT) Structures in T Cell Activation?

Our lab recently discovered uniquely large (multiple micrometres) ring‐shaped cellular structures composed of endosomal sorting complexes required for transport (ESCRT) proteins. These structures are formed by tissue infiltrating fibroblasts, dendritic cells (DCs) and macrophages but only in specific culturing conditions, notably in dense three‐dimensional collagen matrices or without serum on glass supports. We also found that the structures are devoid of F‐actin and form at membrane damage sites, suggesting a role of these structures in membrane repair. Another possibility is that these structures have a role in the immunological synapses (IS) with T cells, because they surround clusters of tetraspanins and integrins that have known roles at the IS. Therefore, we tested the hypothesis that giant ESCRT structures are present at the IS between DCs and T cells and contribute to its stability or signaling. Although we occasionally observed enrichment of ESCRT proteins at the interface between DCs, we do not observe this at the IS between human monocyte‐derived DCs (moDCs) and allogenic T cells. Thus, our data do not support a role for the giant worm‐shaped ESCRT structures at the IS, and suggest that they solely are involved in plasma membrane stability and integrity.