NINJ1 (ninjurin 1) is a transmembrane protein that serves as the critical executioner of plasma membrane rupture (PMR) during lytic cell death processes. NINJ1 contains two transmembrane regions and mediates PMR in response to diverse forms of cell death including pyroptosis, necroptosis, and apoptosis 1. The protein functions through oligomerization of its evolutionarily conserved extracellular domain, forming filamentous assemblies that create amphipathic structures with hydrophilic and hydrophobic sides 2. These NINJ1 filaments can stably cap membrane edges and actively cut and release membrane disks, leading to membrane fragmentation rather than simple pore formation 3. NINJ1 also regulates plasma membrane fragility under mechanical strain, with membrane NINJ1 levels inversely correlating with the force required for membrane rupture 4. During inflammatory cell death and PANoptosis, NINJ1 acts as an executioner independent of other pore-forming proteins like gasdermin D, enabling release of large proinflammatory molecules including DAMPs that propagate inflammatory responses 5. This discovery overturns the traditional view of PMR as a passive osmotic process, establishing NINJ1 as an active mediator of membrane integrity loss with significant implications for inflammatory diseases.