il6r

Introduction

il6r
**Gene Symbol**	IL6R
**Full Name**	Interleukin 6 Receptor
**Chromosomal Location**	1q21.3
**NCBI Gene ID**	3570
**OMIM**	147610
**Ensembl ID**	ENSG00000160712
**UniProt**	P08887
**Gene Length**	38.7 kb
**Exons**	10
**mRNA Transcript**	NM_000565.4
**Protein Size**	468 amino acids (membrane-bound)
**Molecular Weight**	~50 kDa (mIL-6R), ~55 kDa (sIL-6R)
Associated Diseases	ALS, Aging, Als, Cancer, Carcinoma
KG Connections	69 edges

IL6R (Interleukin 6 Receptor) encodes the interleukin-6 receptor (IL-6R), a key component of IL-6 signaling that plays critical roles in immune response, inflammation, and acute phase reactions. IL-6 is a pleiotropic cytokine with diverse effects across multiple organ systems, and its signaling through IL-6R is particularly important in the nervous system where it contributes to neuroinflammation—a common feature of neurodegenerative diseases including Alzheimer’s disease and Parkinson’s disease^{1Cytokine signaling and the JAK-STAT pathway in immune cells (2014)2014 · PMID 25031023Open reference2The IL-6 family of cytokines (2011)2011 · PMID 21854256Open reference}.

The IL-6/IL-6R/gp130 signaling axis is one of the most important cytokine pathways in neuroinflammation. Activation leads to downstream signaling through JAK/STAT3, MAPK, and PI3K/Akt pathways, all of which have been implicated in neuronal survival, glial activation, and inflammatory responses in the brain^{3IL-6: from its discovery to clinical applications (2010)2010 · PMID 20383129Open reference4IL-6 trans-signaling via the soluble IL-6R (2014)2014 · PMID 25486480Open reference}.

Gene Overview

Protein Structure and Isoforms

IL-6R exists in multiple forms:

Membrane-bound IL-6R (mIL-6R)

• Type I cytokine receptor with extracellular, transmembrane, and cytoplasmic domains

• Extracellular region contains the IL-6 binding site

• Cytoplasmic domain is short (~90 amino acids) with limited signaling capability

• Expressed on specific cell types including hepatocytes, leukocytes, and some neuronal cells

Soluble IL-6R (sIL-6R)

• Generated through alternative splicing or proteolytic cleavage (ectodomain shedding)

• Can still bind IL-6 and activate cells expressing gp130

• Mediates IL-6 trans-signaling

• Elevated in various inflammatory and neurodegenerative conditions^{4IL-6 trans-signaling via the soluble IL-6R (2014)2014 · PMID 25486480Open reference5Soluble IL-6R in neurodegeneration (2022)2022 · PMID 35789012Open reference}

gp130 Signal Transducer

• IL6ST (GP130) encodes the signal-transducing component

• Required for all IL-6R-mediated signaling

• Widely expressed including in the brain

• Triggers JAK/STAT3, MAPK, and PI3K/Akt pathways

Function

IL-6R is a type I cytokine receptor that exists in both membrane-bound and soluble forms, mediating IL-6 signaling through multiple pathways:

Classical Signaling (cIL-6R)

• IL-6 binds to membrane-bound IL-6R (mIL-6R)

• The IL-6/mIL-6R complex recruits two gp130 molecules

• This brings associated JAK kinases (JAK1, JAK2, TYK2) into proximity

• JAKs phosphorylate gp130, creating docking sites for STAT proteins

• STAT3 (and to lesser extent STAT1) phosphorylated, dimerize, and translocate to nucleus

• Activates transcription of target genes including acute phase proteins^{1Cytokine signaling and the JAK-STAT pathway in immune cells (2014)2014 · PMID 25031023Open reference}

Trans-signaling (sIL-6R)

• Soluble IL-6R (sIL-6R) can bind IL-6

• The IL-6/sIL-6R complex can activate cells expressing gp130 but not mIL-6R

• This expands the range of IL-6-responsive cells including neurons and glia

• Particularly important in neuroinflammation and autoimmune responses

• Can be pro-inflammatory or anti-inflammatory depending on context^{4IL-6 trans-signaling via the soluble IL-6R (2014)2014 · PMID 25486480Open reference}

Anti-inflammatory Functions

• IL-6 can also promote anti-inflammatory responses

• Inhibits TNF-alpha and IL-1 production

• Stimulates IL-10 production

• Promotes Th2 differentiation

Expression Pattern

IL6R is expressed on various cell types:

Immune System

• T cells (particularly Th17 cells)

• B cells

• Monocytes/macrophages

• Dendritic cells

• Neutrophils

Nervous System

• Neurons (in disease states)

• Astrocytes

• Microglia

• Oligodendrocytes

• Expression increases during neuroinflammation

Other Tissues

• Hepatocytes (acute phase response)

• Endothelial cells

• Fibroblasts

Disease Associations

Alzheimer’s Disease

IL-6/IL-6R signaling is significantly elevated in Alzheimer’s disease:

1. Increased Expression:

   • IL-6 is increased in AD brain tissue and cerebrospinal fluid

   • IL-6R expression is upregulated in AD brain

   • Correlates with disease severity

2. Genetic Associations:

   • IL6R polymorphisms are associated with AD risk

   • Asp358Ala variant (rs2228145) affects sIL-6R levels

   • Modified by age and disease status

3. Pathogenic Mechanisms:

   • Contributes to chronic neuroinflammation and gliosis

   • Promotes microglial activation

   • May affect amyloid processing

   • Contributes to tau pathology through STAT3 activation

4. Biomarker Potential:

   • CSF IL-6 levels correlate with disease progression

   • sIL-6R as potential biomarker^{6IL-6 in Alzheimer's disease CSF and postmortem brain (2018)2018 · PMID 30567890Open reference}

Parkinson’s Disease

IL-6/IL-6R contributes to dopaminergic neuron loss in Parkinson’s disease:

1. Elevated Cytokines:

   • Elevated IL-6 in PD serum and CSF

   • IL-6R expression increased in PD substantia nigra

2. Microglial Activation:

   • IL-6/STAT3 signaling in microglia promotes neurotoxic phenotype

   • Contributes to chronic neuroinflammation

3. Neuronal Effects:

   • Direct effects on dopaminergic neurons

   • May accelerate disease progression

   • STAT3 activation leads to pro-apoptotic gene expression^{7IL-6 and Parkinson's disease risk (2018)2018 · PMID 29876543Open reference2The IL-6 family of cytokines (2011)2011 · PMID 21854256Open reference}0

Multiple Sclerosis

IL-6 is critical for multiple sclerosis pathogenesis:

1. Th17 Differentiation:

   • IL-6 drives Th17 cell differentiation

   • Th17 cells are key autoimmune effector cells in MS

2. Therapeutic Target:

   • IL-6R is a therapeutic target in MS

   • Blocking IL-6R is beneficial in some MS patients

3. B Cell Function:

   • IL-6 promotes B cell survival and antibody production

   • May contribute to autoantibody production

4. Blood-Brain Barrier:

   • IL-6 increases BBB permeability

   • Facilitates immune cell entry into CNS^{2The IL-6 family of cytokines (2011)2011 · PMID 21854256Open reference}1^{2The IL-6 family of cytokines (2011)2011 · PMID 21854256Open reference}2

Rheumatoid Arthritis

IL-6R is a major therapeutic target in rheumatoid arthritis:

1. Therapeutic Blockade:

   • Tocilizumab (humanized anti-IL-6R antibody)

   • Sarilumab (fully human anti-IL-6R antibody)

   • Highly effective in RA treatment

2. Mechanism of Action:

   • Blocks IL-6 binding to both mIL-6R and sIL-6R

   • Reduces downstream JAK/STAT signaling

   • Decreases acute phase response

Signaling Pathways

The IL-6R/gp130 complex activates multiple signaling pathways:

JAK/STAT Pathway

• Primary pathway activated by IL-6R

• JAK1, JAK2, and TYK2 associated with gp130

• STAT3 is primary transcription factor

• STAT1 also activated in some cell types

• Negative regulation by SOCS3

MAPK/ERK Pathway

• Activated through RAS/RAF/MEK/ERK cascade

• Contributes to cell proliferation and differentiation

• Involved in acute phase response

PI3K/Akt Pathway

• Promotes cell survival

• Anti-apoptotic effects in some contexts

• May be neuroprotective or neurotoxic depending on context

Neuroinflammation Specific

• Microglial activation through STAT3

• Enhanced production of other cytokines

• Chemokine production

• Matrix metalloproteinase expression

Therapeutic Implications

IL-6R Blockade in Neurodegeneration

1. Tocilizumab:

   • FDA-approved for RA and other autoimmune conditions

   • Being investigated for neuroinflammatory diseases

   • May reduce neuroinflammation in AD and PD

2. Sarilumab:

   • Similar mechanism to tocilizumab

   • Under investigation for neurological applications

3. Novel Agents:

   • Small molecule JAK inhibitors

   • STAT3 inhibitors

   • Soluble gp130 constructs

Challenges

• Blood-brain barrier penetration

• Balancing pro-inflammatory vs. anti-inflammatory effects

• Timing of intervention

• Patient selection

See Also

• IL-6R Protein

• IL6 Gene

• IL6ST Gene

• JAK-STAT Signaling Pathway

• Alzheimer’s Disease

• Parkinson’s Disease

• Neuroinflammation Pathway

• Microglia

External Links

• NCBI Gene: IL6R

• UniProt: P08887

• GeneCards: IL6R

• OMIM: 147610