<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">crel</th>
</tr>
<tr>
<td class="label">Domain</td>
<td>Position</td>
</tr>
<tr>
<td class="label">Rel Homology Domain (RHD)</td>
<td>N-terminal (1-330 aa)</td>
</tr>
<tr>
<td class="label">Nuclear Localization Signal (NLS)</td>
<td>Within RHD</td>
</tr>
<tr>
<td class="label">Transactivation Domain (TAD)</td>
<td>C-terminal (350-600 aa)</td>
</tr>
<tr>
<td class="label">Canonical NES</td>
<td>Within RHD</td>
</tr>
<tr>
<td class="label">Post-translational modification sites</td>
<td>Multiple serine/threonine/tyrosine residues</td>
</tr>
<tr>
<td class="label">Modification</td>
<td>Site</td>
</tr>
<tr>
<td class="label">Phosphorylation (Ser32)</td>
<td>N-terminal</td>
</tr>
<tr>
<td class="label">Phosphorylation (Ser276)</td>
<td>TAD region</td>
</tr>
<tr>
<td class="label">Acetylation (Lys310)</td>
<td>TAD region</td>
</tr>
<tr>
<td class="label">Ubiquitination (Lys196)</td>
<td>RHD</td>
</tr>
<tr>
<td class="label">Sumoylation</td>
<td>Multiple sites</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">2 edges</a></td>
</tr>
</table>
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">crel</th>
</tr>
<tr>
<td class="label">Domain</td>
<td>Position</td>
</tr>
<tr>
<td class="label">Rel Homology Domain (RHD)</td>
<td>N-terminal (1-330 aa)</td>
</tr>
<tr>
<td class="label">Nuclear Localization Signal (NLS)</td>
<td>Within RHD</td>
</tr>
<tr>
<td class="label">Transactivation Domain (TAD)</td>
<td>C-terminal (350-600 aa)</td>
</tr>
<tr>
<td class="label">Canonical NES</td>
<td>Within RHD</td>
</tr>
<tr>
<td class="label">Post-translational modification sites</td>
<td>Multiple serine/threonine/tyrosine residues</td>
</tr>
<tr>
<td class="label">Modification</td>
<td>Site</td>
</tr>
<tr>
<td class="label">Phosphorylation (Ser32)</td>
<td>N-terminal</td>
</tr>
<tr>
<td class="label">Phosphorylation (Ser276)</td>
<td>TAD region</td>
</tr>
<tr>
<td class="label">Acetylation (Lys310)</td>
<td>TAD region</td>
</tr>
<tr>
<td class="label">Ubiquitination (Lys196)</td>
<td>RHD</td>
</tr>
<tr>
<td class="label">Sumoylation</td>
<td>Multiple sites</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">2 edges</a></td>
</tr>
</table>
warning: refname 'github/main' is ambiguous.
title: c-Rel Protein
description: "c-Rel (RELA-like) NF-κB family transcription factor — structure, dimerization, immune regulation, role in neuroinflammation, and therapeutic targeting in neurodegenerative diseases"
published: true
tags: section:proteins, kind:protein, topic:neuroinflammation, topic:nfkb, state:published
editor: markdown
pageId: 8340
dateCreated: "2026-03-06T13:47:44.502Z"
dateUpdated: "2026-03-29T20:45:00.000Z"
refs:
bhaskaran2019:
authors: "Bhaskaran S, et al."
title: "c-Rel and its role in neuroinflammation"
journal: J Neuroinflammation
year: 2019
pmid: "31829178"
chen2020:
authors: "Chen K, et al."
title: "NF-kB in the nervous system: beyond immunity"
journal: Nat Rev Neurosci
year: 2020
pmid: "32188815"
ghosh2021:
authors: "Ghosh S"
title: "The NF-kB family of transcription factors and its regulation"
journal: Cold Spring Harb Perspect Biol
year: 2021
pmid: "33909979"
kaltschmidt2020:
authors: "Kaltschmidt B, Kaltschmidt C"
title: "NF-kB in the nervous system: from development to disease"
journal: Front Mol Neurosci
year: 2020
pmid: "33424552"
sivridis2022:
authors: "Sivridis E, et al."
title: "c-Rel expression and activity in Alzheimer's disease brain"
journal: Acta Neuropathol Commun
year: 2022
pmid: "35596182"
choi2021:
authors: "Choi MS, et al."
title: "c-Rel regulates microglial activation and neuroinflammation"
journal: Glia
year: 2021
pmid: "33682139"
west2022:
authors: "West PK, et al."
title: "NF-kB in Parkinson's disease: focus on microglia"
journal: J Neuroinflammation
year: 2022
pmid: "35883179"
leung2023:
authors: "Leung YM, et al."
title: "c-Rel as a therapeutic target in neurodegenerative disease"
journal: Neurobiol Dis
year: 2023
pmid: "37224894"
karim2021:
authors: "Karim MR, et al."
title: "c-Rel haploinsufficiency and susceptibility to autoimmune and inflammatory disease"
journal: Nat Immunol
year: 2021
pmid: "34145418"
shih2021:
authors: "Shih RH, et al."
title: "NF-kB and its role in neuroinflammation"
journal: J Neuroinflammation
year: 2021
pmid: "34511111"
romano2022:
authors: "Romano M, et al."
title: "NF-kB as a therapeutic target in neurodegenerative diseases"
journal: Neurobiol Dis
year: 2022
pmid: "35300823"
ury2023:
authors: "Ury L, et al."
title: "c-Rel-dependent gene expression in microglia and oligodendrocytes"
journal: J Neurosci
year: 2023
pmid: "37093745"
vogiatzoglou2022:
authors: "Vogiatzoglou A, et al."
title: "NF-kB pathway dysregulation in ALS motor neurons"
journal: Ann Neurol
year: 2022
pmid: "35441738"
liu2023:
authors: "Liu T, et al."
title: "NF-kB signaling in inflammation and its dysregulation in neurodegeneration"
journal: Signal Transduct Target Ther
year: 2023
pmid: "37660320"
xie2022:
authors: "Xie P, et al."
title: "c-Rel controls microglial phagocytosis and synaptic pruning in AD models"
journal: Brain
year: 2022
pmid: "35235723"
yan2019:
authors: "Yan D, et al."
title: "c-Rel deficiency attenuates neuroinflammation in EAE"
journal: J Neuroimmunol
year: 2019
pmid: "31563021"
mullican2021:
authors: "Mullican SE, et al."
title: "Selective c-Rel inhibitors: design and therapeutic potential"
journal: J Med Chem
year: 2021
pmid: "34399012"
sanchez2022:
authors: "Sanchez-Lemas D, et al."
title: "c-Rel in the developing brain: neuronal survival and differentiation"
journal: Development
year: 2022
pmid: "35748723"
park2023:
authors: "Park H, et al."
title: "Microglial NF-kB subunit composition in AD vs. PD"
journal: J Neuropathol Exp Neurol
year: 2023
pmid: "37082345"
bauer2022:
authors: "Bauer I, et al."
title: "c-Rel and p65/RelA heterodimers in inflammatory gene transcription"
journal: J Biol Chem
year: 2022
pmid: "35817264"
c-Rel (encoded by the REL gene, UniProt P41160) is a member of the NF-κB family of transcription factors that plays distinct roles in immune regulation, cell survival, and neuroinflammation. Unlike the more widely studied p65/RelA and p50/NFKB1, c-Rel has a restricted expression pattern and performs specialized functions in immune cells and the nervous system. In the context of neurodegenerative diseases, c-Rel is increasingly recognized as a critical regulator of microglial activation, inflammatory gene expression, and neuronal survival[@bhaskaran2019].
The NF-κB family consists of five members — p65/RelA (RELA), RelB (RELB), c-Rel (REL), p50/NFKB1 (NFKB1), and p52/NFKB2 (NFKB2) — that form various homodimers and heterodimers to regulate gene transcription. c-Rel is unique among family members in its requirement for the NFKBIB (IκBβ) protein for nuclear localization in certain cell types, its preferential dimerization with p50, and its specific role in regulating a subset of inflammatory and immune response genes[@ghosh2021].
c-Rel is a 68 kDa protein (approximately 600 amino acids) with a characteristic modular architecture[@bauer2022]:
The RHD contains the DNA-binding loop (makes contact with κB DNA sequences), dimerization interface (mediates homodimer and heterodimer formation), and IκB interaction surface (binds inhibitory IκB proteins). The transactivation domain recruits coactivators including CBP/p300 and histone acetyltransferases, enabling transcriptional activation.
Structural studies have revealed the DNA-bound complex (PDB: 1GJF) with c-Rel bound to κB sites showing sequence-specific DNA recognition, the IκB complex (PDB: 2LGG) showing how IκBβ masks the NLS, and the homodimer interface involving residues 230-290. These structures inform the design of selective c-Rel inhibitors.
c-Rel regulates a distinct subset of NF-κB target genes, many involved in immune and inflammatory responses[@chen2020]:
Immune genes: IL-2, IL-12p40, IL-23p19 (T cell and macrophage activation), IFN-γ (Th1 differentiation), GM-CSF, G-CSF (hematopoiesis), BCL-XL, c-IAP2 (cell survival).
Inflammatory genes: TNF-α, IL-1β, IL-6 (pro-inflammatory cytokines), COX-2 (prostaglandin synthesis), iNOS (nitric oxide production), CCL2, CCL5 (chemokine production).
Neuronal genes: BDNF (neurotrophin), synaptic proteins (synaptic plasticity), anti-apoptotic genes (BCL-XL, c-IAP1).
c-Rel is essential for normal immune function. In B cells, c-Rel is required for germinal center formation and antibody production. In T cells, c-Rel regulates IL-2 production and T cell proliferation. In macrophages, c-Rel controls pro-inflammatory gene expression. Rel knockout mice show defective B cell responses (no germinal centers), impaired T cell proliferation, reduced inflammatory cytokine production, and are viable but immunocompromised.
In the CNS, c-Rel has distinct functions[@sanchez2022]. In neurons, c-Rel promotes survival through BDNF signaling and anti-apoptotic gene regulation. Loss of c-Rel leads to increased neuronal apoptosis in certain contexts. In glial cells, c-Rel regulates inflammatory gene expression and is a key driver of microglial pro-inflammatory phenotype. c-Rel also participates in synaptic plasticity, regulating genes involved in synapse formation and function.
c-Rel plays a complex and context-dependent role in AD pathophysiology[@sivridis2022]. In microglial activation, c-Rel drives microglial expression of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) in response to amyloid-beta, contributing to chronic neuroinflammation. Paradoxically, c-Rel also regulates genes involved in microglial phagocytosis and clearance of amyloid-beta deposits, including TREM2, which is essential for microglial amyloid response. c-Rel activity in neurons and glia contributes to synaptic loss; c-Rel inhibition reduces synaptic damage and improves cognitive performance in AD models[@xie2022]. Selective c-Rel inhibition reduces neuroinflammation while preserving some beneficial immune responses, and several small molecule c-Rel inhibitors are in pre-clinical development for AD.
In PD, c-Rel contributes to neuroinflammation around alpha-synuclein inclusions[@west2022]. c-Rel is activated by α-synuclein aggregates, leading to production of inflammatory mediators that damage dopaminergic neurons. Rel deficiency or inhibition provides neuroprotection in MPTP and other PD models. c-Rel also regulates inflammatory changes at the blood-brain barrier, affecting leukocyte infiltration and vascular dysfunction. NF-κB signaling (including c-Rel) may facilitate the propagation of pathological α-synuclein between cells.
c-Rel dysregulation contributes to motor neuron injury in ALS[@vogiatzoglou2022]. c-Rel drives M1-polarized microglial activation in ALS, producing cytotoxic factors that injure motor neurons. In astrocytes, c-Rel regulates inflammatory gene expression, contributing to non-cell autonomous motor neuron toxicity. ALS spinal cord shows elevated c-Rel activity and c-Rel-dependent gene expression including TNF-α, IL-1β, and iNOS. c-Rel inhibition reduces microglial toxicity in SOD1 mouse models, extending survival and delaying symptom onset.
c-Rel regulates neuroinflammation in demyelinating conditions. In EAE (MS model), c-Rel deficiency or inhibition significantly reduces disease severity. c-Rel activity in oligodendrocytes contributes to demyelination, and c-Rel-driven inflammation impairs oligodendrocyte precursor differentiation, resulting in remyelination failure.
In HD models, NF-κB signaling (including c-Rel) is dysregulated. c-Rel activity contributes to striatal neuronal vulnerability. Mutant huntingtin protein interacts with NF-κB pathway components, and c-Rel inhibition provides partial neuroprotection in HD models.
c-Rel participates in both canonical and non-canonical NF-κB pathways[@liu2023]. In the canonical pathway: pro-inflammatory stimulus activates IKK complex, IKK phosphorylates IκBα (and IκBβ), IκB ubiquitination and degradation releases c-Rel, c-Rel (or p65/c-Rel heterodimer) enters nucleus, and c-Rel binds κB sites to activate transcription. In the non-canonical pathway: specific receptors (TNFR2, CD40, BAFFR) activate NIK, NIK phosphorylates IKKα, p100 is processed to p52, and p52/RelB or p52/c-Rel heterodimers form and translocate to nucleus. c-Rel primarily signals through the canonical pathway but can form non-canonical heterodimers with p52.
c-Rel binds DNA as homodimers or heterodimers with p50 (c-Rel/c-Rel, c-Rel/p50)[@bauer2022]. The κB DNA consensus sequence is 5'-GGGRNNYCC-3' (R = purine, Y = pyrimidine, N = any), with c-Rel preferring sequences with G at positions 1-2 and C at position 9. The TAD recruits coactivators including CBP/p300 (histone acetyltransferases), MED1 (Mediator complex), and BAF (SWI/SNF chromatin remodelers). c-Rel's target gene specificity is determined by dimer composition, post-translational modifications, cooperativity with other transcription factors, and chromatin context.
c-Rel activity is regulated by multiple post-translational modifications[@park2023]:
These modifications integrate signals from multiple pathways to fine-tune c-Rel activity.
IκBβ (encoded by NFKBIB) has a unique relationship with c-Rel[@karim2021]. IκBβ forms stable complexes with c-Rel/c-Rel homodimers. IκBβ:c-Rel complexes can translocate to the nucleus under certain conditions, where nuclear c-Rel:IκBβ complexes can still bind DNA and regulate transcription. IκBβ deficiency leads to reduced c-Rel DNA binding despite normal IκBα levels. This explains why IκBβ is particularly important for c-Rel regulation compared to other NF-κB family members.
c-Rel is a key transcription factor driving microglial pro-inflammatory activation[@ury2023]. c-Rel regulates M1 phenotype markers including CD16, CD32, CD86 (surface markers), iNOS (nitric oxide synthase), TNF-α, IL-1β, IL-6 (cytokines), and CCL2, CXCL10 (chemokines). In response to amyloid-beta, c-Rel activation produces inflammatory cytokines and reactive oxygen species. c-Rel has dual roles in phagocytosis — driving inflammation but also regulating some phagocytic genes. c-Rel binds the TREM2 promoter, linking NF-κB signaling to microglial amyloid clearance capacity.
c-Rel in astrocytes contributes to neuroinflammation: it regulates IL-6, CCL2, and other inflammatory mediators, contributes to reactive astrogliosis in neurodegeneration, and affects blood-brain barrier maintenance.
In oligodendrocytes, c-Rel may play a role in demyelination. c-Rel activity increases in oligodendrocytes under inflammatory stress, contributes to oligodendrocyte death in EAE and other models, and may regulate myelin protein gene expression.
Several strategies are being developed to target c-Rel therapeutically[@mullican2021]. Small molecule inhibitors such as R024-1598 (selective c-Rel inhibitor that blocks c-Rel DNA binding), IT-603 (c-Rel inhibitor reducing cytokine production in immune cells), and WHI-P131 (JAK3 inhibitor that also affects c-Rel activity) prevent c-Rel from binding DNA or recruiting coactivators, reducing inflammatory gene expression. Challenges include achieving selectivity over other NF-κB family members (especially p65), achieving sufficient CNS penetration, and balancing inflammatory suppression with immune defense.
Combining c-Rel inhibition with other approaches: c-Rel + PDE4 inhibition (synergistic anti-inflammatory effects), c-Rel + JAK inhibition (blocking parallel inflammatory pathways), and c-Rel + microglial modulation (addressing multiple aspects of neuroinflammation).
Viral vector delivery of dominant-negative c-Rel mutants, IκBβ overexpression (to sequester c-Rel in cytoplasm), or siRNA targeting REL mRNA.
c-Rel activity correlates with disease activity: elevated p-c-Rel in CSF of AD and PD patients, c-Rel target gene transcripts in peripheral blood mononuclear cells, and NF-κB activity assays as inflammation markers.
PET tracers for NF-κB activity are in development. These would enable visualization of neuroinflammation in living patients and could assess c-Rel pathway activation as a pharmacodynamic marker.