- Receptor‑interacting serine/threonine‑protein kinase 3 (RIPK3) is a core signalling kinase that orchestrates necroptosis, a regulated form of necrotic cell death characterised by membrane rupture and inflammation. RIPK3 acts downstream of death receptors, pattern‑recognition receptors and cellular stress pathways, integrating inflammatory cues to determine whether a cell undergoes necroptosis or survives. Its essential role in activating MLKL makes RIPK3 a defining component of the necroptotic machinery.
- RIPK3 contains an N‑terminal kinase domain and a C‑terminal RIP homotypic interaction motif (RHIM). The RHIM enables RIPK3 to interact with other RHIM‑containing proteins, most notably RIPK1. Under conditions where caspase‑8 is active, RIPK1 and RIPK3 interactions are suppressed, favouring apoptosis. However, when caspase‑8 is inhibited—during viral infection, inflammation or genetic deficiency—RIPK1 and RIPK3 assemble into the necrosome, a signalling complex that drives necroptosis.
- Within the necrosome, RIPK3 undergoes autophosphorylation and phosphorylates the pseudokinase MLKL, the terminal effector of necroptosis. Phosphorylated MLKL oligomerises, translocates to the plasma membrane and inserts into lipid bilayers, forming disruptive pores. This causes ionic imbalance, osmotic swelling, membrane rupture and release of DAMPs (damage‑associated molecular patterns), triggering inflammation and immune activation.
- RIPK3 signalling is tightly integrated with other regulated cell‑death pathways. Crosstalk with apoptosis ensures necroptosis is activated only when apoptotic machinery is compromised. Interaction with pyroptosis and ferroptosis shapes inflammatory outcomes during infection and tissue damage. RIPK3 also interfaces with metabolic and redox pathways, linking necroptosis to mitochondrial ROS production and cellular stress responses.
- Beyond necroptosis, RIPK3 participates in inflammatory signalling independent of MLKL. It can activate NF‑κB, promote cytokine production and modulate innate immune responses. These non‑death functions highlight RIPK3 as a broader regulator of inflammation and host defence.
- Dysregulation of RIPK3 contributes to numerous diseases. Excessive RIPK3 activity drives tissue damage in ischemia–reperfusion injury, neurodegeneration, pancreatitis, inflammatory bowel disease and viral infection. Conversely, impaired RIPK3 signalling can weaken host defence against pathogens that inhibit apoptosis. Because of its central role, RIPK3 is a major therapeutic target, and inhibitors of RIPK3 or MLKL are being explored for inflammatory and degenerative disorders.
- In summary, RIPK3 is a central necroptotic kinase that activates MLKL and drives regulated necrotic cell death. Through necrosome formation, MLKL phosphorylation and inflammatory signalling, RIPK3 shapes immunity, inflammation and disease progression. Its pivotal role in cell‑death biology makes RIPK3 a key focus of modern molecular and biomedical research.
