RIPK3 Protein

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RIPK3 Protein

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">RIPK3 Protein</th>
</tr>
<tr>
<td class="label">Feature</td>
<td>RIPK1</td>
</tr>
<tr>
<td class="label">Kinase domain</td>
<td>Catalytically active</td>
</tr>
<tr>
<td class="label">RHIM domain</td>
<td>Present</td>
</tr>
<tr>
<td class="label">Death domain</td>
<td>Present (C-terminus)</td>
</tr>
<tr>
<td class="label">Necrosome role</td>
<td>Initiator</td>
</tr>
<tr>
<td class="label">Kinase inhibitors</td>
<td>Multiple in development</td>
</tr>
<tr>
<td class="label">Interactor</td>
<td>Relationship</td>
</tr>
<tr>
<td class="label">[RIPK1](/proteins/ripk1-protein)</td>
<td>Necrosome partner</td>
</tr>
<tr>
<td class="label">[MLKL](/proteins/mlkl-protein)</td>
<td>Phosphorylation substrate</td>
</tr>
<tr>
<td class="label">DAI/ZBP1</td>
<td>RHIM-containing sensor</td>
</tr>
<tr>
<td class="label">TRIF</td>
<td>TLR3/4 adaptor</td>
</tr>
<tr>
<td class="label">PGAM5</td>
<td>Mitochondrial phosphatase</td>
</tr>
<tr>
<td class="label">[Drp1](/proteins/drp1-protein)</td>
<td>Mitochondrial fission</td>
</tr>
<tr>
<td class="label">TAK1</td>
<td>Kinase interaction</td>
</tr>
<tr>
<td class="label">FADD</td>
<td>Apoptosis adaptor</td>
</tr>
<tr>
<td class="label">Caspase-8</td>
<td>Protease</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/ad" s

...

RIPK3 Protein

<div style="float: right; margin: 0 0 1em 1em; padding: 1em; background: #f8f9fa; border: 1px solid #a2a9b1; border-radius: 5px; font-size: 0.9em; width: 280px;">
RIPK3 
Receptor-Interacting Serine/Threonine-Protein Kinase 3
<hr>
Symbol: RIPK3 
UniProt: [Q9Y572](https://www.uniprot.org/uniprot/Q9Y572) 
Gene: [RIPK3](/genes/ripk3) 
Molecular Weight: 56.8 kDa (517 aa) 
Location: Cytoplasm 
Expression: Low in CNS, elevated in disease 
PDB: [4M66](https://www.rcsb.org/structure/4M66), [7Q5V](https://www.rcsb.org/structure/7Q5V)
</div>

Overview

Receptor-interacting serine/threonine-protein kinase 3 (RIPK3) is the essential downstream executor of [necroptosis](/mechanisms/necroptosis), a regulated form of programmed necrotic cell death. Unlike its upstream partner [RIPK1](/proteins/ripk1-protein), RIPK3 functions primarily as a kinase that executes the necroptotic death program by phosphorylating and activating [MLKL](/proteins/mlkl-protein) [@sun2012]. The formation of the RIPK1-RIPK3 necrosome creates an amyloid-like signaling platform that drives the necrotic cell death cascade implicated in multiple neurodegenerative diseases.

RIPK3 is increasingly recognized as a critical mediator of neuronal death in Alzheimer's disease, Parkinson's disease, ALS, and other neurological conditions. Unlike RIPK1, which has been successfully targeted in clinical trials with kinase inhibitors like GSK2982772, RIPK3 inhibitors remain in preclinical development despite strong mechanistic rationale for neuroprotection.

Structure and Domains

RIPK3 is a 517-amino acid serine/threonine protein kinase with a molecular weight of 56.8 kDa. Its domain architecture includes:

Kinase Domain (Residues 1-286)

The N-terminal kinase domain contains the canonical serine/threonine kinase fold with:

ATP-binding pocket: Distinct from RIPK1, enabling selective inhibition
Activation loop: Contains Thr182, the critical autophosphorylation site
DYG motif: Characteristic Asp-Tyr-Gly sequence required for catalytic activity
Unique inserts: Differentiate RIPK3 from other RIP family members

The kinase domain is responsible for:

Autophosphorylation at Thr182, Ser227, and other sites
Transphosphorylation of RIPK1 within the necrosome
Phosphorylation of MLKL at Thr357/Ser358

RHIM Domain (Residues 386-467)

The RIP Homotypic Interaction Motif (RHIM) mediates:

Necrosome formation: RHIM-RHIM interactions with RIPK1 create the core signaling complex
Amyloid assembly: RIPK1 and RIP3 form alternating filamentous structures through RHIM domain interactions, creating functional amyloid assemblies that act as signaling platforms [@li2012]
Protein recruitment: Additional RHIM-containing proteins (TRIF, DAI/ZBP1) can be recruited

The RHIM domain contains:

Four β-strands forming a β-sheet interface
Hydrophobic residues critical for amyloid formation
The conserved "I/V-x-Q-x-G" motif

C-Terminal Region (Residues 468-517)

The C-terminal region:

Contains regulatory elements
May participate in protein-protein interactions
Shows less conservation across species

Structural Comparison with RIPK1

Normal Function

Necroptosis Execution

RIPK3 is the central executor of necroptosis, functioning through a well-characterized signaling cascade:

Step 1 — Necrosome Formation
Upon activation of [TNFR1](/proteins/tnfr1-protein) or other death receptors, RIPK1 is recruited to the signaling complex. If ubiquitination fails or necrostatin-1 is absent, RIPK1 recruits RIPK3 through RHIM-RHIM interactions. This forms the necrosome — a higher-order amyloid signaling platform [@li2012].

Step 2 — RIPK3 Activation
Within the necrosome:

RIPK1 phosphorylates RIPK3 at Thr182
RIPK3 autophosphorylates at Ser227 and other sites
The activation loop becomes fully functional

Step 3 — MLKL Recruitment and Phosphorylation
Activated RIPK3 binds and phosphorylates [MLKL](/proteins/mlkl-protein):

Phosphorylation at Thr357 and Ser358
Conformational change and oligomerization
Plasma membrane translocation

Step 4 — Membrane Disruption
Phosphorylated MLKL forms oligomers that:

Bind phosphatidylinositol phosphates in the plasma membrane
Create ion channels
Cause membrane rupture and necrotic cell death

Alternative Signaling Roles

Beyond necroptosis, RIPK3 participates in several non-necroptotic pathways:

NF-κB Activation
RIPK3 can activate NF-κB independently of necroptosis [@dannappel2021], promoting inflammatory gene expression. This may contribute to chronic neuroinflammation in neurodegenerative diseases.

Inflammasome Regulation
RIPK3 interacts with the [NLRP3 inflammasome](/entities/nlrp3-inflammasome) and may prime or activate inflammasome signaling, linking necroptosis to interleukin-1β production.

Metabolic Regulation
RIPK3 influences [mTOR](/mechanisms/mtor-signaling-pathway) signaling and cellular metabolism, with implications for neuronal energy homeostasis.

Physiological Roles

In non-diseased states, RIPK3:

Defense against pathogens: Necroptosis limits viral and bacterial replication
Development: Ripk3 knockout mice are viable but susceptible to infection
Tissue homeostasis: Protective in some contexts (e.g., intestinal epithelium)
Immune regulation: Modulates inflammatory responses

The relatively restricted expression of RIPK3 in the CNS under normal conditions suggests that necroptosis is not a major pathway in healthy neurons, but becomes activated in disease contexts.

Role in Neurodegeneration

RIPK3-mediated necroptosis has emerged as a significant contributor to neuronal death across multiple neurodegenerative diseases. The restricted expression of RIPK3 in the healthy brain becomes elevated in disease states, making it an attractive therapeutic target.

Alzheimer's Disease

RIPK3 activation in [Alzheimer's disease](/diseases/alzheimers-disease) contributes to pathology through multiple mechanisms:

Elevated Expression

RIPK3 expression is significantly increased in AD brain tissue
Levels correlate with disease severity
Both neurons and microglia show increased RIPK3

Pathological Co-localization

RIPK3 co-localizes with [neurofibrillary tangles](/entities/neurofibrillary-tangles) containing hyperphosphorylated [tau](/proteins/tau)
Found in proximity to [amyloid-beta](/proteins/amyloid-beta) plaques
Microglial RIPK3 associated with plaque周边

Neuronal Death Mechanisms

Direct necroptotic execution in vulnerable neurons
Contribution to chronic neuroinflammation through microglial activation
Synaptic loss via necroptotic mechanisms

Evidence from Models

RIPK3 deficiency reduces pathology in APP/PS1 mouse models
Pharmacological inhibition improves cognitive function
Necroptosis markers present in human AD brain tissue [@caccamo2017]

Parkinson's Disease

In [Parkinson's disease](/diseases/parkinsons-disease), RIPK3-mediated necroptosis contributes to dopaminergic neuron loss:

Dopaminergic Neuron Vulnerability

Human dopaminergic neurons express RIPK3 and are susceptible to necroptosis
Post-mortem PD brain shows elevated RIPK3 expression
The vulnerability is amplified by [α-synuclein](/proteins/alpha-synuclein) pathology

Pathogenic Triggers

[α-synuclein](/proteins/alpha-synuclein) aggregates may activate RIPK3-dependent pathways
Mitochondrial dysfunction promotes necrosome formation
Oxidative stress from dopamine metabolism contributes

Neuroprotection

RIPK3 knockout protects dopaminergic neurons in MPTP models
RIPK3 deficiency prevents motor deficits in PD models [@hu2020]
Combination with RIPK1 inhibition shows additive benefits

Amyotrophic Lateral Sclerosis (ALS)

RIPK3 plays a critical role in [ALS](/diseases/amyotrophic-lateral-sclerosis) pathogenesis:

Motor Neuron Death

RIPK3 and MLKL activation observed in ALS spinal cord
Both sporadic and familial ALS show necrosome activation
Elevated p-RIPK3 in patient tissue

Pathogenic Mechanisms

[SOD1](/proteins/sod1-protein) mutations trigger necroptosis
[TDP-43](/mechanisms/tdp-43-proteinopathy) pathology associated with RIPK3 activation
[C9orf72](/entities/c9orf72) hexanucleotide expansions may promote necroptosis

Therapeutic Potential

RIPK3 inhibition extends survival in SOD1 mouse models
Combined RIPK1/RIPK3 inhibition more effective than either alone
Addresses both neuronal death and neuroinflammation [@re2014]

Huntington's Disease

RIPK3 contributes to [Huntington's disease](/diseases/huntingtons) pathology:

RIPK3 activation observed in striatal neurons
Mutant [huntingtin](/proteins/huntingtin-protein) aggregates may trigger necroptotic signaling
Synaptic dysfunction involves necroptotic mechanisms
RIPK3 inhibition shows protective effects in models [@momoi2019]

Multiple Sclerosis and Demyelinating Diseases

RIPK3-mediated necroptosis of [oligodendrocytes](/entities/oligodendrocytes):

Contributes to demyelination in multiple sclerosis
RIPK3 deficiency reduces pathology in EAE models
Axonal degeneration involves necroptotic pathways

Stroke and Traumatic Brain Injury

In acute CNS injury:

Rapid necrosome formation post-ischemia
Secondary injury mediated by RIPK3
[Blood-brain barrier](/entities/blood-brain-barrier) disruption via MLKL
Therapeutic window for RIPK3 inhibition [@meng2021]

Therapeutic Targeting

RIPK3 Kinase Inhibitors

Several RIPK3 inhibitors have been developed but none have reached clinical trials:

GSK'872 (GSK2399872A)

Potent and selective RIPK3 inhibitor
Successfully inhibits necroptosis in cell and animal models
Used extensively as research tool
Not advanced to clinical development

HS1371

RIPK3 inhibitor with good selectivity
Protective in ischemia-reperfusion injury models
Shows neuroprotection in experimental settings

Zabaditer

Early clinical-stage RIPK3 inhibitor
Limited CNS data available

Compound 3z

RIPK3-specific inhibitor
Shows efficacy in inflammatory disease models

Challenges in RIPK3 Targeting

Kinase-Independent Functions

RIPK3 has scaffold roles beyond catalytic activity
Complete blockade may require targeting both functions
Must consider non-necroptosis pathways

Selectivity Challenges

RIPK3 kinase domain has similarities to other kinases
Achieving selectivity over RIPK1 is critical
Small molecule development challenging

Expression Patterns

RIPK3 not expressed in all cell types
Cell-type specific targeting may be needed
Must consider immune function implications

BBB Penetration

CNS delivery required for neurodegenerative indications
Must balance polarity, MW, and lipophilicity
Similar challenges to RIPK1 inhibitors

Dual Targeting Strategies

Given the interconnected nature of cell death pathways, combination approaches may be superior:

RIPK1 + RIPK3 Inhibition

Complete blockade of necroptosis pathway
Addresses both initiation and execution
Most comprehensive neuroprotection

RIPK1 + Caspase Inhibition

Blocks both necroptosis and apoptosis
Addresses two major cell death pathways
Broader neuroprotection

RIPK3 + Anti-inflammatory

Targets both cell death and inflammation
Addresses key components of neurodegeneration
May allow lower doses of each

Current Clinical Landscape

Unlike RIPK1 inhibitors (GSK2982772 completed Phase I), no RIPK3 inhibitors have reached clinical trials for any indication. The development has focused on:

Tool compounds for research
Proof-of-concept in preclinical models
Understanding RIPK3 biology in human disease

This represents both a gap and an opportunity for RIPK3-targeted neuroprotective therapies.

Key Interactions

Expression in the CNS

Normal Brain Expression

Under physiological conditions, RIPK3 expression in the CNS is relatively low:

Minimal expression in healthy neurons
Low basal levels in microglia
Higher expression in certain immune populations

Disease-Associated Changes

In neurodegenerative diseases, RIPK3 expression dramatically increases:

Neuronal expression increases 5-10 fold
Microglial RIPK3 becomes prominently activated
Expression correlates with pathological burden

This disease-specific upregulation makes RIPK3 an attractive target — inhibiting it should have limited effects on normal physiology while providing significant neuroprotection in disease.

Biomarkers

RIPK3 activity can be monitored through:

Phospho-RIPK3 (Thr182)

Direct measure of RIPK3 activation
Detectable in human brain tissue
Correlates with disease severity

Necrosome Formation

RIPK1-RIPK3 complex detection
Indicates active necroptosis signaling
Can be measured in CSF

Phospho-MLKL (Thr357)

Downstream marker of necroptosis execution
More stable than phospho-RIPK3
Indicates completion of death pathway

These biomarkers could be useful for patient selection and response monitoring in clinical trials.

Research Tools and Models

Knockout Mice

Ripk3^-/- mice are viable and fertile
Resistant to necroptosis-inducing stimuli
Used extensively to demonstrate RIPK3 requirement

Transgenic Models

RIPK3 overexpression models
Humanized RIPK3 knock-in mice
Disease-specific crosses

Inhibitors

GSK'872 (cell-permeable)
HS1371 (selective)
ZVSH (RIPK3 inhibitor)

Pathway & Interaction Diagram

Interactive diagram showing RIPK3 key relationships in the SciDEX knowledge graph (15 connections shown).

Mermaid diagram (expand to render)

External Links

[UniProt: Q9Y572](https://www.uniprot.org/uniprot/Q9Y572)
[PDB Structures](https://www.rcsb.org/search?q=uniprot:Q9Y572)
[GeneCards: RIPK3](https://www.genecards.org/cgi-bin/carddisp.pl?gene=RIPK3)
[NCBI Gene: 8767](https://www.ncbi.nlm.nih.gov/gene/8767)

References

[Sun L et al. Mixed lineage kinase domain-like protein mediates necrosis signaling downstream of RIP3 kinase. Cell. 2012;148(1-2):213-227](https://doi.org/10.1016/j.cell.2012.01.007)

[Ofengeim D, Yuan J. Regulation of RIP1 kinase signalling at the crossroads of inflammation and cell death. Nat Rev Mol Cell Biol. 2013;14(11):727-736](https://doi.org/10.1038/nrm3683)

[Li J et al. The RIP1/RIP3 necrosome forms a functional amyloid signaling complex required for programmed necrosis. Cell. 2012;150(2):339-350](https://doi.org/10.1016/j.cell.2012.06.019)

[Caccamo A et al. Necroptosis drives Alzheimer's disease pathology in vivo. J Neurosci. 2017;37(47):9254-9269](https://doi.org/10.1523/JNEUROSCI.1867-17.2017)

[Re DB et al. Necroptosis drives motor neuron death in models of both sporadic and familial ALS. Neuron. 2014;81(5):1001-1018](https://doi.org/10.1016/j.neuron.2014.01.011)

[Kaiser WJ et al. Toll-like receptor 3-mediated necrosis via TRIF, RIP3, and MLKL. J Biol Chem. 2013;288(43):31268-31279](https://doi.org/10.1074/jbc.M113.462341)

[Dannappel M et al. RIPK3 maintains tumor-initiating cell function in diffuse large B-cell lymphoma via NF-κB. J Exp Med. 2021;218(8):e20210474](https://doi.org/10.1084/jem.20210474)

[He S et al. Structural basis for the unique function of RIPK3. Cell Death Differ. 2019;26(9):1720-1738](https://doi.org/10.1038/s41418-018-0252-y)

[Moriwaki K et al. The necroptosis adaptor RIPK3 is an essential regulator of acute kidney injury. Cell Death Discov. 2018;4:21](https://doi.org/10.1038/s41420-018-0024-0)

[Degterev A et al. Chemical inhibitor of nonapoptotic cell death with therapeutic potential for ischemic brain injury. Nat Chem Biol. 2005;1(2):112-119](https://doi.org/10.1038/nchembio.711)

[Linkermann A et al. Regulated necrosis: the expanding network of non-apoptotic cell death pathways. Nat Rev Mol Cell Biol. 2014;15(2):135-147](https://doi.org/10.1038/nrm3737)

[Pasparakis M, Vandenabeele P. Necroptosis and its role in inflammatory diseases. Nature. 2015;517(7534):311-320](https://doi.org/10.1038/nature14191)

[Vitner EB et al. RIPK3 as a potential therapeutic target for neurodegenerative diseases. Expert Opin Ther Targets. 2016;20(8):967-975](https://doi.org/10.1080/14728222.2016.1181747)

[Hu Y et al. RIPK3 deficiency blocks neuronal death in Parkinson's disease models. Cell Death Dis. 2020;11(8):664](https://doi.org/10.1038/s41419-020-2597-7)

[Meng Y et al. RIPK3 mediates chronic neurodegeneration in traumatic brain injury. Neurotherapeutics. 2021;18(3):1735-1751](https://doi.org/10.1007/s13311-021-01040-5)

[You Z et al. Targeting necroptosis: a promising therapeutic strategy for Alzheimer's disease. Neural Regen Res. 2022;17(8):1743-1753](https://doi.org/10.4103/1673-5374.332822)

[Momoi M et al. Therapeutic potential of necroptosis inhibition in Huntington's disease. Brain Res Bull. 2019;149:77-84](https://doi.org/10.1016/j.brainresbull.2019.03.019)

[Weyand CM et al. Necroptosis in the pathogenesis of rheumatic diseases. Nat Rev Rheumatol. 2018;14(8):453-467](https://doi.org/10.1038/s41584-018-0033-5)

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RIPK3 Protein

RIPK3 Protein

RIPK3 Protein

Overview

Structure and Domains

Kinase Domain (Residues 1-286)

RHIM Domain (Residues 386-467)

C-Terminal Region (Residues 468-517)

Structural Comparison with RIPK1

Normal Function

Necroptosis Execution

Alternative Signaling Roles

Physiological Roles

Role in Neurodegeneration

Alzheimer's Disease

Parkinson's Disease

Amyotrophic Lateral Sclerosis (ALS)

Huntington's Disease

Multiple Sclerosis and Demyelinating Diseases

Stroke and Traumatic Brain Injury

Therapeutic Targeting

RIPK3 Kinase Inhibitors

Challenges in RIPK3 Targeting

Dual Targeting Strategies

Current Clinical Landscape

Key Interactions

Expression in the CNS

Normal Brain Expression

Disease-Associated Changes

Biomarkers

Research Tools and Models

Pathway & Interaction Diagram

See Also

External Links

References