Receptor-interacting protein 3 (RIP3, also known as RIPK3) is a serine-threonine protein involved in the regulation of inflammatory signaling and cell death. RIPK3, also named as RIP3, a Ser/Thr kinase of RIP (Receptor Interacting Protein) family, is a nucleocytoplasmic shuttling protein and its unconventional nuclear localization signal (NLS, 442-472 aa) is sufficient to trigger apoptosis in the nucleus (PMID: 18533105). It has 3 isoforms produced by alternative splicing.

What is the molecular weight of RIP3? Is RIP3 post-translationally modified?

The molecular weight of RIP3 is 57 kDa. During the induction of necroptosis, RIP3 migrates slower in SDS-PAGE due to its phosphorylation (PMID: 19524512). Additionally, RIP3 can be a subject of poly-ubiquitination, when targeted for degradation.

Are there any splice isoforms of RIP3?

Apart from full-length RIP3, there are two reported splice isoforms of RIP3: RIP3β and RIP3γ, and 28 and 25 kDa, respectively (PMID: 15896315).

What is the subcellular localization of RIP3?

RIP3 can shuttle between the cytoplasm and the nucleus. Although RIP3 forms necrosomes in the cytoplasm, a recent study suggests that the phosphorylation of RIP3, required for necroptosis, may also occur in the nucleus (PMID: 30271893). Additionally, the induction of necrosis by reactive oxygen species can cause transient translocation of RIP3 to mitochondria (PMID: 25206339).

What is the role of RIP3 in cell death (necroptosis)?

Activation of RIP3 kinase is required for the induction of necroptosis (PMID: 19524512, 19524513 and 19498109). Activation of RIP3 can be induced by interferons, death ligands, or by Toll-like receptors in response to pathogens. That leads to the phosphorylation of RIP3 and the formation of a β-amyloid-like protein complex. Phosphorylated RIP3 acts downstream by phosphorylation of MLKL (PMID: 30131615).

How to study necroptosis in a cell-based system?

The choice of the cell line is important. Many commonly used immortalized cell types are derived from cancers and may have very low RIL3 expression level (PMID: 25952668). Those cell lines are not going to be responsive to necrotic stimuli. A few of the examined cell types have high RIP3 levels: Jurkat, CCRF-CEM, U937, L929 cells, and mouse embryonic fibroblasts (PMID: 19524512). Good necroptosis readouts reflect an increased level of RIP3 protein and its phosphorylation.