C1R encodes complement C1r, a serine protease component of the C1 complex in the classical complement pathway. C1r is activated following C1q binding to immune complexes, triggering a proteolytic cascade that leads to C3 convertase formation and downstream complement activation. In the brain, C1r is expressed by microglia and astrocytes, contributing to complement-mediated synaptic pruning and neuroinflammatory responses.
The C1R gene encodes a component of the complement system, part of the innate immune system involved in inflammation and immune response.
Gene SymbolC1R
Full NameComplement Component 1, R Subcomponent (C1r)
Chromosomal Location12p13.31
Ensembl IDENSG00000159403
Associated DiseasesSystemic Lupus Erythematosus, Age-Related Macular Degeneration
The C1R gene encodes complement component 1, r subcomponent (C1r), a serine protease that is part of the C1 complex. C1r is the enzymatic component of the C1 complex, which also includes C1q (recognition), C1s (effector protease), and two more C1r molecules.
The C1 complex (C1qr₂s₂) initiates the classical complement pathway:
- C1q binds to its targets (antibodies, pathogens, DAMPs)
- This triggers conformational changes that activate C1r
- Activated C1r then cleaves and activates C1s
- Activated C1s then cleaves C4 and C2, generating C4b2a (C3 convertase)
- Alzheimer's Disease: C1r is part of the complement cascade that is activated in AD brain and contributes to neuroinflammation.
- Parkinson's Disease: Complement activation involving C1r is implicated in dopaminergic neuron degeneration.
- Systemic Lupus Erythematosus: Genetic variants in C1R may influence disease susceptibility.
- Brain: Expressed by microglia and astrocytes, upregulated in neuroinflammation
- Liver: Primary site of synthesis
- Immune cells: Macrophages, monocytes
- Nataf et al., Complement activation in neurodegenerative diseases (2000)
- Ricklin et al., Complement in disease (2013)
- Janeway et al., Immunobiology (9th ed., 2016)
- Ricklin et al., Complement in disease (2013)
- Merle et al., Complement system (2015)