Antigen cross-presentation by dendritic cells (DC) stimulates cytotoxic T cell activation to promote immunity to intracellular pathogens, viruses and cancer. Phagocytosed antigens generate potent T cell responses, but the signalling and trafficking pathways regulating their cross-presentation are unclear. Here, we show that ablation of the store-operated-Ca2+-entry regulator STIM1 in mouse myeloid cells impairs cross-presentation and DC migration in vivo and in vitro. Stim1ablation reduces Ca2+ signals, cross-presentation, and chemotaxis in mouse bone-marrow-derived DCs without altering cell differentiation, maturation or phagocytic capacity. Phagosomal pH homoeostasis and ROS production are unaffected by STIM1 deficiency, but phagosomal proteolysis and leucyl aminopeptidase activity, IRAP recruitment, as well as fusion of phagosomes with endosomes and lysosomes are all impaired. These data suggest that STIM1-dependent Ca2+ signalling promotes the delivery of endolysosomal enzymes to phagosomes to enable efficient cross-presentation.
Paula Nunes-Hasler, Sophia Maschalidi, Carla Lippens, Cyril Castelbou, Samuel Bouvet, Daniele Guido, Flavien Bermont, Esen Y. Bassoy, Nicolas Page, Doron Merkler, Stéphanie Hugues, Denis Martinvalet, Bénédicte Manoury & Nicolas Demaurex
How Amira-Avizo Software is used
Alignment, segmentation and 3D reconstruction of FIB-SEM images was performed using Amira software.