Protein / target
Complement C1s subcomponent
Protein at a glance
Biological role
Serine-type endopeptidase
Strongest disease association
Coronary Artery Disease
Therapeutic position
Established drug target
Derived from structured UniProt, Open Targets and literature data on this page.
Protein profile
Canonical identity and biological annotation from UniProt.
Function overview
Component of the complement C1 complex, a multiprotein complex that initiates the classical pathway of the complement system, a cascade of proteins that leads to phagocytosis and breakdown of pathogens and signaling that strengthens the adaptive immune system.
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Component of the complement C1 complex, a multiprotein complex that initiates the classical pathway of the complement system, a cascade of proteins that leads to phagocytosis and breakdown of pathogens and signaling that strengthens the adaptive immune system (PubMed:11445589, PubMed:16169853, PubMed:417728, PubMed:467643, PubMed:6271784, PubMed:6282646, PubMed:6319179, PubMed:70787, PubMed:9422791). C1S is activated following association of the C1 complex with immunoglobulins (IgG or IgM) complexed with antigens to form antigen-antibody complexes on the surface of pathogens (PubMed:34155115). C1S is cleaved and activated by C1R to generate C1s subcomponent heavy and light chains (PubMed:11445589, PubMed:6271784). C1s subcomponent light chain then cleaves and activates C2 and C4, the next components of the classical complement pathway (PubMed:16169853, PubMed:467643, PubMed:6282646, PubMed:6319179, PubMed:6906228, PubMed:70787, PubMed:9422791)
Subcellular location
Domains and Gene Ontology detail (18)Hide
Domains & features
Gene Ontology
- Cblood microparticle
- Ccell surface
- Ccomplement component C1 complex
- Cextracellular region
- Cextracellular space
- Csymbiont cell surface
- Fcalcium ion binding
- Fidentical protein binding
- Fserine-type endopeptidase activity
- Pcomplement activation, classical pathway
- Pinnate immune response
- Pproteolysis
Biological roles
What this protein does, drawn together from its UniProt function, Gene Ontology terms and Reactome pathways.
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Immune signalling
- ·Component of the complement C1 complex, a multiprotein complex that initiates the classi…
- ·symbiont cell surface
- ·innate immune response
Proteolysis
- ·serine-type endopeptidase activity
- ·proteolysis
Concepts derived from UniProt GO Reactome — each badge above shows which sources supported that role.
Approved medicines with mapped indications
Approved therapies targeting this protein, grouped by what they are approved to treat — the disease-first view of the medicines below. Relationships come from the canonical approved-indication graph (ChEMBL phase-4), the same source as the drug cards.
2 medicines meet Open Targets' target-level approved-medicine definition; the 1 shown here are those on this page with a canonical approved disease indication in the graph. Approved indications from ChEMBL (phase-4), via the canonical drug→disease graph.
Drugs targeting this protein
How approved and investigational drugs engage this protein — mechanism and action type, direct vs complex targeting, and how broadly each acts across other targets. A drug-first view (the section above groups the approved ones disease-first); direct binders with few recorded targets are listed first.
ChEMBL mechanism, action type, target identity and approved indications. Open Targets clinical status.
Translational evidence
Why this target matters therapeutically, strongest evidence first. Disease associations are gene-level (via the gene that encodes this protein) and open into the full confidence synthesis; the development universe, tractability and safety annotations are target-level, from Open Targets.
Strongest disease associations · via encoding gene C1S
Gene-level evidence surfaced through the gene C1S that encodes this protein — not a direct protein–disease relationship. Ranked by Forefront's causal-directness weighting, so genetically- and clinically-evidenced diseases lead over ones that merely share the literature.
View evidence synthesis (3)Hide
This ranking differs from Open Targets' own: re-weighting moves genetically-evidenced diseases above more heavily co-mentioned ones. The evidence agreement range shows how closely the independent evidence families agree — it is not a statistical confidence interval, and nothing here is fitted to outcome data. Derived from Open Targets evidence types under Forefront weighting; the per-type scores above show the calculation.
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Drug development
2 compounds recorded · 2 approved
View all recorded compounds (2)Hide
Open Targets known-drugs universe. Drug name and highest clinical stage only — the disease relationship is NOT read from this slice (it carries trial-context noise); approved indications come from the canonical graph above.
Tractability
Small molecules — Emerging
Antibodies — Strong
Protein degraders — Emerging
Other modalities — Strong
View underlying tractability evidence (10)Hide
Raw Open Targets tractability assessment buckets, by modality.
Clinical trials
Trials of drugs that target this protein — reached indirectly through those drugs, so a trial listed here studies the drug, not the protein. Ranked by active status, then clinical phase and recency, and spread across the targeting drugs.
ClinicalTrials.gov via the drug-target graph.
What's happening now
Recent therapeutic activity around this target — regulatory actions, clinical trials and safety signals for a drug that targets this protein, plus publications where such a drug is a genuine subject. Every item is reached indirectly through the drug, not the protein itself; incidental mentions (a paper that merely measures a drug) and press items are excluded.
- Regulatory approval
Approval: Enjaymo (EMA)
Objective event titles are shown unmodified; the event kind and significance line are derived from structured fields. Forefront AttentionEvent stream aggregating Europe PMC Regulatory filings ClinicalTrials.gov.
Related family literature
Papers about “Serine Proteases” — a broader family this protein belongs to. Shown as context; not counted as papers specifically about this protein.
Europe PMC literature, reached through curated HGNC family membership. Membership is a taxonomic relationship — it does not imply this protein participates in every mechanism these papers discuss.