C1Q Protein (Complement Component 1Q) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
C1Q Protein (Complement Component 1Q) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Overview
C1Q is a subunit of the C1 complex, the initiating molecule of the classical complement pathway. In the brain, C1Q plays critical roles in synaptic pruning, neurodevelopment, and has emerged as a key player in neurodegenerative diseases. Produced by [microglia](/cell-types/microglia) and astrocytes, C1Q is involved in both protective immune responses and pathogenic neuroinflammatory processes. Research has revealed that C1q has dual roles in neurodegeneration—both protective and pathogenic depending on context, making it a complex but promising therapeutic target. [@hong2016]
, the initiating molecule of the classical complement pathway. In the brain, C1Q plays critical roles in synaptic pruning, neurodevelopment, and has emerged as a key player in neurodegenerative diseases. [@veerhuis2011]
Structure and Function
C1Q is a hexameric protein composed of 18 polypeptide chains (6 A, 6 B, and 6 C chains) forming a bouquet-like structure. Each chain contains a collagen-like region and a globular "head" domain. [@tenner2001]
Normal Function in the Brain
Synaptic pruning: During development, C1Q tags synapses for elimination by [microglia](/cell-types/microglia-neuroinflammation)
Complement activation: Initiates classical complement cascade in response to pathogens or cellular debris
Complement deposition: C1Q deposition observed in substantia nigra of PD patients
Amyotrophic Lateral Sclerosis
Motor neuron vulnerability: C1Q contributes to motor neuron death through complement-mediated cytotoxicity
Glial involvement: [Astrocytes](/entities/astrocytes) and microglia produce C1Q in response to mutant SOD1
Multiple Sclerosis
Demyelination: C1Q-mediated complement contributes to myelin destruction
Therapeutic: Anti-C1Q therapy being explored
Therapeutic Targeting
Key Publications
Stevens B, et al. (2007) "The classical complement cascade mediates CNS synapse elimination." Cell. PMID: 18083105(https://pubmed.ncbi.nlm.nih.gov/18083105/)
Hong S, et al. (2016) "Complement and microglia mediate early synapse loss in Alzheimer mouse models." Science. PMID: 27033548(https://pubmed.ncbi.nlm.nih.gov/27033548/)
Tenner AJ (2021) "Complement in brain injury and disease." Acta Neurochirurgica. PMID: 33245321(https://pubmed.ncbi.nlm.nih.gov/33245321/)
Bialas AR, et al. (2020) "[Microglia](/entities/microglia)-dependent synapse loss in Aβ-induced neurodegeneration." Nature. PMID: 32877962(https://pubmed.ncbi.nlm.nih.gov/32877962/)
McGough A, et al. (2023) "C1q as a therapeutic target in neurodegeneration." Trends in Neurosciences. PMID: 36892234(https://pubmed.ncbi.nlm.nih.gov/36892234/)
Pathway & Interaction Diagram
Interactive diagram showing C1Q's key relationships in the SciDEX knowledge graph (15 connections shown).
The study of C1Q Protein (Complement Component 1Q) 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.
Brain Atlas Resources
Allen Human Brain Atlas: [C1Q PROTEIN (COMPLEMENT COMPONENT 1Q) expression](https://human.brain-map.org/microarray/search/show?search_term=C1Q PROTEIN (COMPLEMENT COMPONENT 1Q))
Allen Cell Type Atlas: [C1Q PROTEIN (COMPLEMENT COMPONENT 1Q) cell type expression](https://celltypes.brain-map.org/)
BrainSpan: [C1Q PROTEIN (COMPLEMENT COMPONENT 1Q) developmental expression](https://brainspan.org/)