C1Q Protein (Complement Component 1q)

C1Q Protein (Complement Component 1q)

Introduction

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">C1Q Protein (Complement Component 1q)</th>
</tr>
<tr>
<td class="label">Approach</td>
<td>Status</td>
</tr>
<tr>
<td class="label">Anti-C1Q antibodies (Amylyx AMX0035)</td>
<td>Clinical Trials</td>
</tr>
<tr>
<td class="label">Complement inhibitors</td>
<td>Research</td>
</tr>
<tr>
<td class="label">Microglial modulation</td>
<td>Research</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/ad" style="color:#ef9a9a">AD</a>, <a href="/wiki/ali" style="color:#ef9a9a">ALI</a>, <a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">ALZHEIMER</a>, <a href="/wiki/alzheimer's-disease" style="color:#ef9a9a">ALZHEIMER'S DISEASE</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1048 edges</a></td>
</tr>
</table>

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 Protein (Complement Component 1q)

Introduction

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">C1Q Protein (Complement Component 1q)</th>
</tr>
<tr>
<td class="label">Approach</td>
<td>Status</td>
</tr>
<tr>
<td class="label">Anti-C1Q antibodies (Amylyx AMX0035)</td>
<td>Clinical Trials</td>
</tr>
<tr>
<td class="label">Complement inhibitors</td>
<td>Research</td>
</tr>
<tr>
<td class="label">Microglial modulation</td>
<td>Research</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/ad" style="color:#ef9a9a">AD</a>, <a href="/wiki/ali" style="color:#ef9a9a">ALI</a>, <a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">ALZHEIMER</a>, <a href="/wiki/alzheimer's-disease" style="color:#ef9a9a">ALZHEIMER'S DISEASE</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1048 edges</a></td>
</tr>
</table>

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
• Synapse homeostasis: Mediates activity-dependent synaptic refinement
• Neural development: Critical for proper brain wiring during critical periods

Role in Neurodegenerative Diseases

Alzheimer's Disease

C1Q is heavily implicated in AD pathophysiology:

• [Aβ](/proteins/amyloid-beta)-mediated complement activation: [Aβ](/proteins/amyloid-beta) peptides directly bind and activate C1Q, triggering the complement cascade
• Synaptic loss: C1Q tags synapses for microglial elimination, contributing to early synaptic loss
• Synaptic vulnerability: Pre-synaptic terminals show increased C1Q binding in AD brain
• Mouse model studies: C1Q knockout mice show reduced Aβ-induced synapse loss and memory deficits
• Therapeutic target: Anti-C1Q antibodies in clinical trials for AD

Parkinson's Disease

• Dopaminergic neuron vulnerability: C1Q localizes to Lewy bodies and participates in [α-synuclein](/proteins/alpha-synuclein) aggregation
• Microglial activation: C1Q enhances α-synuclein-induced microglial inflammation
• 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

Pathway & Interaction Diagram

Interactive diagram showing C1Q's key relationships in the SciDEX knowledge graph (15 connections shown).

See Also

• [Complement System](/entities/complement-system)
• [Microglia](/mechanisms/disease-associated-microglia)
• [Synaptic Dysfunction](/mechanisms/synaptic-dysfunction-pathway)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• ["Amyotrophic Lateral Sclerosis"](/diseases/amyotrophic-lateral-sclerosis)

External Links

• [UniProt: P02787 (C1QA)](https://www.uniprot.org/uniprotkb/P02787)
• [GeneCards: C1QA](https://www.genecards.org/cgi-bin/carddisp.pl?gene=C1QA)
• [Complement in AD Review](https://pubmed.ncbi.nlm.nih.gov/?term=C1q+Alzheimer+complement)

See Also

• [Complement System](/entities/complement-system)
• [Microglia](/cell-types/microglia)
• [Synaptic Dysfunction Pathway](/mechanisms/synaptic-dysfunction-pathway)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)

Background

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/)

External Links

• [NCBI Gene: C1Q](https://www.ncbi.nlm.nih.gov/gene/712)
• [UniProt: C1QA](https://www.uniprot.org/uniprot/P02787)

References