biostudies-literatureAndoh MMEXT | Japan Society for the Promotion of ScienceMEXT | Japan Society for the Promotion of Science (JSPS)Japan Agency for Medical Research and DevelopmentMEXT | JST | Exploratory Research for Advanced TechnologyMEXT | JST | Exploratory Research for Advanced Technology (ERATO)Japan Agency for Medical Research and Development (AMED)918https://www.ebi.ac.uk/biostudies/studies/S-EPMC11754728biostudies-literatureUnknown16(1)Caspases are known to mediate neuronal apoptosis during brain development. However, here we show that nonapoptotic activation of caspase-3 at presynapses drives microglial synaptic phagocytosis. Real-time observation and spatiotemporal manipulation of synaptic caspase-3 in the newly established, mouse-derived culture system demonstrate that increased neuronal activity triggers localized presynaptic caspase-3 activation, facilitating synaptic tagging by complements. High-resolution live imaging reveals that caspase-3 activation promotes synapse-selective complement-dependent microglial phagocytosis without axonal shearing. Furthermore, activity-dependent caspase-3 activation at inhibitory presynapses induces microglial phagocytosis in mice and increases seizure susceptibility. This increaseNature communicationsNonapoptotic caspase-3 guides C1q-dependent synaptic phagocytosis by microglia.PMC117547282383621821H0477424H00567JPMJER180120H0589723H04766Andoh MKoyama RAraki TMiura MIkegaya YShinoda NTaira YTakeuchi HKasahara YfalseNonapoptotic caspase-3 guides C1q-dependent synaptic phagocytosis by microglia.Caspases are known to mediate neuronal apoptosis during brain development. However, here we show that nonapoptotic activation of caspase-3 at presynapses drives microglial synaptic phagocytosis. Real-time observation and spatiotemporal manipulation of synaptic caspase-3 in the newly established, mouse-derived culture system demonstrate that increased neuronal activity triggers localized presynaptic caspase-3 activation, facilitating synaptic tagging by complements. High-resolution live imaging reveals that caspase-3 activation promotes synapse-selective complement-dependent microglial phagocytosis without axonal shearing. Furthermore, activity-dependent caspase-3 activation at inhibitory presynapses induces microglial phagocytosis in mice and increases seizure susceptibility. This increase2025-01-01T00:00:00Z2025 Jan2025-04-18T14:26:59.963Z2025-04-07T00:36:08.264ZS-EPMC117547283984344510.1038/s41467-025-56342-7