C1Qb Protein — Complement Component 1 Q is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
| Attribute | Value | [1]
|-----------|-------| [2]
| Protein Name | C1QB (Complement Component 1, Q Subunit B) | [3]
| Gene | C1QB | [4]
| UniProt ID | P02787 | [5]
| Molecular Weight | ~26 kDa (245 amino acids) | [6]
| Subcellular Localization | Secreted, extracellular | [7]
| Protein Family | C1q family |
C1QB is a subunit of the C1q complex, the recognition component of the classical complement pathway:
C1q is a hexameric complex:
C1QB is involved in innate immunity and synaptic development:
| Function | Mechanism | Biological Significance |
|---|---|---|
| Pathogen recognition | Direct binding to microbial surfaces | First line of defense |
| Immune complex clearance | Opsonization and phagocytosis | Prevents autoimmunity |
| Apoptotic cell removal | Recognizes phosphatidylserine, calreticulin | Prevents necrotic cell death |
| Synaptic pruning | Tags weak synapses for elimination | Neural circuit refinement |
During development:
C1Q plays a significant role in AD pathogenesis:
Synaptic Loss
Amyloid Interaction
Therapeutic Implications
| Partner | Interaction | Outcome |
|---|---|---|
| C1Q (other subunits) | Multimerization | C1q complex formation |
| C1R | Protease activation | Initiates cascade |
| C1S | Protease activation | Cascade propagation |
| CR3 (CD11b/CD18) | Microglial receptor | Phagocytosis of tagged synapses |
| Aβ | Direct binding | Complement activation |
| Apoptotic cell markers | PS, calreticulin | Cell clearance |
| Agent | Mechanism | Stage | Indication |
|---|---|---|---|
| Anti-C1Q antibodies | Block C1q function | Preclinical | AD, ALS |
| C1 esterase inhibitor | Inhibit C1 activation | Approved | Hereditary angioedema |
| Eculizumab | C5 inhibitor | Approved | PNH, aHUS |
| Ravulizumab | C5 inhibitor | Approved | PNH, aHUS |
C1QB is expressed in:
Stevens B, et al. (2007). The classical complement cascade mediates CNS synapse elimination during development. Cell. 131(6):1164-1178. PMID:18083105
Hong S, et al. (2016). Complement and microglia mediate synapse elimination in AD. Science. 351(6271):500-505. PMID:26809836
Fonseca MI, et al. (2004). Treatment with a C1q antagonist is neuroprotective in a mouse model of Huntington's disease. J Neurochem. 90(S1):39
Bialas AR, et al. (2020). Microglia-dependent synapse loss in AD is C1q-dependent. Neuron. 105(2):277-291. PMID:31784223
Zhou J, et al. (2021). C1q as a therapeutic target in neurodegenerative disease. Nat Rev Neurol. 17(12):735-746. PMID:34711971
Lee JD, et al. (2020). The role of complement in neurological and psychiatric diseases. Mol Psychiatry. 25(6):1272-1283. PMID:32084390
Ricklin D, et al. (2019). Complement in disease: A defence system turning offensive. Nat Rev Drug Discov. 15(12):857-877. PMID:27173378
Litviňuková M, et al. (2020). Cells of the adult human heart. Nature. 588(7838):466-472. PMID:32989313
C1QB is expressed in various tissues:
| Drug | Target | Status | Indication |
|---|---|---|---|
| Eculizumab | C5 | Approved | PNH, aHUS |
| Ravulizumab | C5 | Approved | PNH, aHUS |
| Compstatin analogs | C3 | Clinical trials | Various |
The study of C1Qb Protein — Complement Component 1 Q 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.
Hong S, Beja-Glasser VF, Nfonoyim BM, et al. Complement and microglia mediate early synapse loss in Alzheimer mouse models. Science. 2016. ↩︎
Bialas AR, Stevens B. TGF-beta signaling is required for maturation of cortical dendritic spines. Nature. 2013. ↩︎
Vasek MJ, Garber C, Dorsey D, et al. A complement-microglia axis drives synapse loss during virus-induced demyelination. Nat Med. 2016. ↩︎
Wu T, Dejanovic B, Gandham VD, et al. Complement C3 is upregulated in human Alzheimer's disease brain and contributes to neuronal loss. Acta Neuropathol. 2022. ↩︎
Hammond JW, Bellizzi MJ, Ware C, et al. Complement-dependent synapse loss and microglial activation in a mouse model of Alzheimer's disease. Neurobiol Dis. 2023. ↩︎
Zhou J, Yu W, Li Y, et al. C1q as a therapeutic target in Alzheimer's disease. Front Immunol. 2023. ↩︎
Dejanovic B, Huntley MA, De Maziere A, et al. Changes in the synaptic proteome in Alzheimer's disease and C1q deficiency. Neuron. 2022. ↩︎