Ultrarapid lytic granule release from CTLs activates Ca <sup>2+</sup> -dependent synaptic resistance pathways in melanoma cells
Liza Filali, Marie-Pierre Puisségur, Kévin Cortacero, Sylvain Cussat‐Blanc, Roxana Khazen, Nathalie Van Acker, François-Xavier Frénois, Arnaud Abreu, Laurence Lamant, Nicolás Meyer, B. Vergier, Sabina Müller, Brienne McKenzie, Salvatore Valitutti
Abstract
Human cytotoxic T lymphocytes (CTLs) exhibit ultrarapid lytic granule secretion, but whether melanoma cells mobilize defense mechanisms with commensurate rapidity remains unknown. We used single-cell time-lapse microscopy to offer high spatiotemporal resolution analyses of subcellular events in melanoma cells upon CTL attack. Target cell perforation initiated an intracellular Ca 2+ wave that propagated outward from the synapse within milliseconds and triggered lysosomal mobilization to the synapse, facilitating membrane repair and conferring resistance to CTL induced cytotoxicity. Inhibition of Ca 2+ flux and silencing of synaptotagmin VII limited synaptic lysosomal exposure and enhanced cytotoxicity. Multiplexed immunohistochemistry of patient melanoma nodules combined with automated image analysis showed that melanoma cells facing CD8 + CTLs in the tumor periphery or peritumoral area exhibited significant lysosomal enrichment. Our results identified synaptic Ca 2+ entry as the definitive trigger for lysosomal deployment to the synapse upon CTL attack and highlighted an unpredicted defensive topology of lysosome distribution in melanoma nodules.