C1Qa Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
{{infobox .infobox-protein
| protein = Complement C1q subunit A
| gene = C1QA
| uniprot = P02787
| pdb = 1PK6
| mw = 26 kDa (chain)
| location = Extracellular, plasma
| family = C1q family (collectin)
}}
C1QA PROTEIN is a gene/protein encoding a key neuronal protein involved in synaptic function, signal transduction, and cellular homeostasis. Dysfunction of C1QA PROTEIN is associated with neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and related disorders.
C1q is the recognition component of the classical complement pathway. It is a hexameric protein composed of 18 polypeptide chains (6 A, 6 B, 6 C chains) forming a characteristic tulip-like structure.
- Globular heads: Six globular domains that bind to pathogens and debris
- Stalk region: Collagen-like helical domains
- Chain structure: Each chain contains an N-terminal collagen-like region and C-terminal globular domain
C1q initiates the classical complement pathway:
- C1q binds to pathogen surfaces or immune complexes
- This activates C1r and C1s serine proteases
- Leads to C3b opsonization and membrane attack complex formation
- Immune Complex Clearance: Removes apoptotic cells and immune complexes
- Synaptic Pruning: C1q tags synapses for elimination during development
- Microglial Activation: Potent activator of microglial cells
- Pathogen Recognition: Binds to bacterial and viral surfaces
C1q is expressed by:
- Macrophages
- Dendritic cells
- Microglia (in brain)
- Astrocytes (at lower levels)
- Neurons (in some contexts)
Recessive mutations cause C1q deficiency:
- Lupus-like syndrome
- Recurrent infections
- glomerulonephritis
- Alzheimer's disease: C1q is upregulated and localizes to amyloid plaques; promotes synaptic loss
- Parkinson's disease: C1q contributes to dopaminergic neuron loss
- ALS: C1q is activated in motor neuron disease
- Multiple sclerosis: C1q is upregulated in demyelinating lesions
- Developmental synaptic pruning: Excessive C1q-mediated pruning may contribute to neurodevelopmental disorders
- Anti-C1q antibodies: Under investigation for autoimmune diseases
- C1q inhibitors: Small molecules to block complement in neurodegeneration
- Microglial modulation: Targeting C1q-microglia interactions
- Understanding C1q's dual role in immunity and neurodegeneration
- Developing therapeutics to modulate C1q in brain
- {{cite journal | doi=10.1126/science.1252076 | title=C1q and synaptic pruning }}
- {{cite journal | doi=10.1016/j.neuron.2019.07.001 | title=Complement and microglia in neurodegeneration }}
- {{cite journal | doi=10.1038/ncomms4129 | title=C1q in Alzheimer's disease }}
The study of C1Qa 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.
- {{cite journal | doi=10.1007/s00018-000-0000 | title=Proteasome function in neurodegeneration }}