:: infobox .infobox-protein
| Protein Name | Interleukin-6 Receptor |
| Gene | IL6R |
| UniProt ID | P08887 |
| Molecular Weight | ~80 kDa (membrane-bound), ~55 kDa (soluble) |
| Subcellular Localization | Cell membrane, Golgi apparatus |
| Family | IL-6 receptor family |
| Diseases | Alzheimer's Disease, Parkinson's Disease, Rheumatoid Arthritis |
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The Interleukin-6 Receptor (IL-6R) is a critical cytokine receptor that plays a significant role in neuroinflammation, a key pathological feature of neurodegenerative diseases including Alzheimer's Disease (AD) and Parkinson's Disease (PD)[1]. IL-6R mediates the cellular response to interleukin-6 (IL-6), a pleiotropic cytokine that participates in both acute phase responses and chronic inflammatory processes[2]. The IL-6R signaling pathway has become an important therapeutic target, with tocilizumab (an IL-6R antagonist) showing promise in clinical trials for various neurological conditions[3].
Interleukin-6 Receptor (IL-6R) is a transmembrane protein encoded by the IL6R gene on chromosome 1q21.3[4]. It exists in two forms: a membrane-bound receptor (mIL-6R) of approximately 80 kDa and a soluble receptor (sIL-6R) generated by proteolytic cleavage or alternative splicing[5]. The membrane-bound IL-6R is expressed on various cell types including hepatocytes, leukocytes, and certain neuronal populations, while the soluble form can bind IL-6 and trigger signaling in cells that express the signal-transducing subunit gp130 but lack IL-6R itself—a phenomenon known as trans-signaling[6].
The IL-6R pathway is particularly relevant to neurodegeneration because chronic neuroinflammation is a hallmark of both AD and PD[7]. Elevated levels of IL-6 and sIL-6R have been detected in the cerebrospinal fluid (CSF) and post-mortem brain tissue of patients with AD and PD, suggesting that dysregulated IL-6 signaling contributes to disease progression[8]. Genetic studies have also identified IL6R variants as risk factors for AD, further supporting its pathogenic role[9].
The IL-6R extracellular domain consists of three distinct regions[10]:
The soluble form (~55 kDa) retains the extracellular domain and can[11]:
IL-6R signaling is essential for hepatic acute phase protein synthesis[12]:
The IL-6R pathway modulates adaptive and innate immunity[13]:
In the central nervous system, IL-6R signaling affects[14]:
IL-6R signaling contributes to AD pathogenesis through multiple mechanisms[15]:
Elevated sIL-6R in CSF correlates with cognitive decline in AD patients, making it a potential biomarker[16].
In PD, IL-6R signaling promotes dopaminergic neuron degeneration[17]:
IL-6R dysregulation is also implicated in[18]:
Several therapeutic agents target IL-6R signaling[19]:
| Drug | Mechanism | Clinical Status |
|---|---|---|
| Tocilizumab | Humanized anti-IL-6R antibody | FDA approved for RA; trials for AD/PD |
| Sarilumab | Fully human anti-IL-6R antibody | FDA approved for RA |
| Siltuximab | Anti-IL-6 chimeric antibody | Trials for various conditions |
Recent and ongoing trials target IL-6R in neurodegeneration[20]:
The study of Il 6R Protein has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
IL-6 and IL-6R in Alzheimer's disease: Implications for future therapeutics (2023) ↩︎
Interleukin-6: Review of its role in immune regulation and disease (2022) ↩︎
Tocilizumab in neurodegenerative diseases: Clinical trials and mechanisms (2023) ↩︎
Soluble IL-6R: Generation and biological significance (2022) ↩︎
IL-6 trans-signaling via soluble IL-6R: Importance for neuroinflammation (2021) ↩︎
Neuroinflammation in Alzheimer's and Parkinson's disease (2023) ↩︎
CSF IL-6 and sIL-6R as biomarkers in neurodegenerative diseases (2022) ↩︎
IL6R genetic variants and Alzheimer's disease risk (2021) ↩︎
ADAM17-mediated shedding of IL-6R in neuroinflammation (2022) ↩︎
Soluble IL-6R as cognitive decline biomarker in AD (2022) ↩︎
IL-6R and neuroinflammation in multiple sclerosis and ALS (2022) ↩︎
IL-6R targeted therapies: From rheumatoid arthritis to neurology (2023) ↩︎
Clinical trials of IL-6R blockade in neurological disorders (2024) ↩︎