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).
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0043129 surfactant homeostasis | IBA GO_REF:0000033 | ACCEPT | 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. Reason: Family-level (IBA) inference matching the established surfactant role of PLUNC/latherin-like proteins. Supporting Evidence: file:FELCA/Feld8/Feld8-uniprot.txt Belongs to the BPI/LBP/Plunc superfamily. Plunc family. |
| GO:0005576 extracellular region | IEA GO_REF:0000044 | ACCEPT | Summary: Fel d 8 is a secreted salivary protein; extracellular localization is appropriate. Reason: Secreted PLUNC-family protein acting in oral/airway secretions. Supporting Evidence: file:FELCA/Feld8/Feld8-uniprot.txt SUBCELLULAR LOCATION: Secreted |
| GO:0008289 lipid binding | IEA GO_REF:0000002 | ACCEPT | 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. Reason: Consistent with the BPI/LBP/PLUNC lipid-binding fold; the defining molecular activity of the family. Supporting Evidence: file:FELCA/Feld8/Feld8-uniprot.txt Lipid binding protein |
| GO:0043129 surfactant homeostasis | IEA GO_REF:0000118 | ACCEPT | Summary: TreeGrafter (IEA) duplicate of the surfactant-homeostasis process inference. Reason: Consistent with the PLUNC-family surfactant role. Supporting Evidence: file:FELCA/Feld8/Feld8-uniprot.txt Belongs to the BPI/LBP/Plunc superfamily. Plunc family. |
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Download this section (compressed HTML)Q: Does Fel d 8 function as a salivary surfactant/antimicrobial like other PLUNC proteins, and what lipids does it bind?
Experiment: 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.
Hypothesis: Fel d 8 is a latherin-like salivary surfactant that lowers surface tension and binds lipids.
Type: biophysical / lipid-binding assay
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