Necroptosis

Necroptosis is a form of regulated necrotic cell death mediated by receptor-interacting serine-threonine kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL) and generally manifests with morphological features of necrosis. Necroptosis is characterized by early loss of plasma membrane integrity, leakage of intracellular contents, and organelle swelling. The cells dying through necroptosis lack the typical apoptotic characteristics, such as membrane blebbing, chromatin condensation, and intranucleosomal DNA cleavage into 180 bp DNA laddering, but may show TUNEL positivity.

Necroptosis triggers innate immune responses by rupturing dead cells and releasing intracellular components, it can be caused by Toll-like receptor (TLR)-3 and TLR-4 agonists, tumor necrosis factor (TNF), certain microbial infections, and T cell receptors. Necroptosis signaling is modulated by receptor-interacting protein kinase (RIPK) 1 when the activity of caspase-8 becomes compromised. Activated death receptors (DRs) cause the activation of receptor-interacting serine-threonine kinase 1 (RIPK1) and the RIPK1 kinase activity-dependent formation of an RIPK1-RIPK3-MLKL, which is complex II. RIPK3 phosphorylates MLKL, ultimately leading to necrosis through plasma membrane disruption and cell lysis.