id: F6K0R4
gene_symbol: Feld8
product_type: PROTEIN
status: DRAFT
taxon:
  id: NCBITaxon:9685
  label: Felis catus
description: >-
  Fel d 8, a secreted salivary protein of the domestic cat belonging to the
  BPI/LBP/PLUNC superfamily (PLUNC family) and a minor cat allergen. PLUNC-family
  proteins are latherin-like, lipid-binding surfactant proteins of oral/airway
  secretions that lower surface tension and participate in airway-surface-liquid
  and surfactant homeostasis and innate mucosal defense. As a PLUNC-family salivary
  allergen Fel d 8 is presumed spread to fur during grooming, where it binds IgE; the
  specific cat tissue of origin is not documented in the UniProt record. Its specific
  molecular ligand and function in the cat are inferred from the PLUNC family rather
  than directly demonstrated (the UniProt entry is unreviewed).
existing_annotations:
- term:
    id: GO:0043129
    label: surfactant homeostasis
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      PLUNC-family (BPI/LBP/PLUNC) proteins act as biological surfactants in
      oral/airway secretions and participate in surfactant/airway-surface-liquid
      homeostasis; phylogenetic inference of this process for Fel d 8 is consistent
      with its family.
    action: ACCEPT
    reason: Family-level (IBA) inference matching the established surfactant role of PLUNC/latherin-like proteins.
    supported_by:
    - reference_id: file:FELCA/Feld8/Feld8-uniprot.txt
      supporting_text: Belongs to the BPI/LBP/Plunc superfamily. Plunc family.
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Fel d 8 is a secreted salivary protein; extracellular localization is appropriate.
    action: ACCEPT
    reason: Secreted PLUNC-family protein acting in oral/airway secretions.
    supported_by:
    - reference_id: file:FELCA/Feld8/Feld8-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Secreted'
- term:
    id: GO:0008289
    label: lipid binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: >-
      BPI/LBP/PLUNC-superfamily proteins bind lipids; the UniProt SubName for this
      entry is literally "Lipid binding protein". Lipid binding is the core
      molecular function consistent with the family fold.
    action: ACCEPT
    reason: Consistent with the BPI/LBP/PLUNC lipid-binding fold; the defining molecular activity of the family.
    supported_by:
    - reference_id: file:FELCA/Feld8/Feld8-uniprot.txt
      supporting_text: Lipid binding protein
- term:
    id: GO:0043129
    label: surfactant homeostasis
  evidence_type: IEA
  original_reference_id: GO_REF:0000118
  qualifier: involved_in
  review:
    summary: TreeGrafter (IEA) duplicate of the surfactant-homeostasis process inference.
    action: ACCEPT
    reason: Consistent with the PLUNC-family surfactant role.
    supported_by:
    - reference_id: file:FELCA/Feld8/Feld8-uniprot.txt
      supporting_text: Belongs to the BPI/LBP/Plunc superfamily. Plunc family.
core_functions:
- description: >-
    Secreted lipid-binding protein of the BPI/LBP/PLUNC (latherin-like) family,
    inferred to act as a biological surfactant in oral/salivary (and airway)
    secretions, contributing to surfactant/airway-surface-liquid homeostasis. The
    specific lipid ligand and detailed mechanism for cat Fel d 8 are family-inferred,
    not directly demonstrated.
  molecular_function:
    id: GO:0008289
    label: lipid binding
  directly_involved_in:
  - id: GO:0043129
    label: surfactant homeostasis
  supported_by:
  - reference_id: file:FELCA/Feld8/Feld8-uniprot.txt
    supporting_text: Belongs to the BPI/LBP/Plunc superfamily. Plunc family.
  - reference_id: file:FELCA/Feld8/Feld8-uniprot.txt
    supporting_text: Lipid binding protein
  locations:
  - id: GO:0005576
    label: extracellular region
  knowledge_gaps:
  - gap_statement: >-
      The specific lipid ligand and the precise physiological role of cat Fel d 8
      are not experimentally established; current annotations are inferred from the
      PLUNC family.
    boundary: >-
      Established: Fel d 8 is a secreted BPI/LBP/PLUNC-family (latherin-like)
      lipid-binding protein. Unknown: its specific lipid cargo and demonstrated
      function in the cat.
    gap_kind:
    - BIOLOGY
    provenance:
    - reference_id: file:FELCA/Feld8/Feld8-uniprot.txt
      supporting_text: Belongs to the BPI/LBP/Plunc superfamily. Plunc family.
proposed_new_terms: []
suggested_questions:
- question: >-
    Does Fel d 8 function as a salivary surfactant/antimicrobial like other PLUNC
    proteins, and what lipids does it bind?
  experts: []
suggested_experiments:
- hypothesis: Fel d 8 is a latherin-like salivary surfactant that lowers surface tension and binds lipids.
  description: >-
    Measure surface-tension reduction by recombinant Fel d 8 (Wilhelmy plate /
    pendant drop) and characterize lipid binding by liposome co-sedimentation and
    lipid-array assays.
  experiment_type: biophysical / lipid-binding assay
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
  findings: []
- id: GO_REF:0000118
  title: TreeGrafter-generated GO annotations
  findings: []
- id: file:FELCA/Feld8/Feld8-uniprot.txt
  title: UniProt entry F6K0R4 (Lipid binding protein / Fel d 8), Felis catus
  findings:
  - statement: Fel d 8 is a secreted BPI/LBP/PLUNC-family lipid-binding protein cat allergen; the entry is unreviewed.
    supporting_text: Belongs to the BPI/LBP/Plunc superfamily. Plunc family.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Unreviewed (TrEMBL) UniProt record; supports PLUNC-family lipid-binding
      classification and secretion. Specific ligand/function is family-inferred and
      recorded as a knowledge gap.