{"uniprot":"Q9H8J5","gene":"MANSC1","name":"MANSC domain-containing protein 1","organism":"Homo sapiens (Human)","status":"dark","length":431,"sequence":"MFFGGEGSLTYTLVIICFLTLRLSASQNCLKKSLEDVVIDIQSSLSKGIRGNEPVYTSTQEDCINSCCSTKNISGDKACNLMIFDTRKTARQPNCYLFFCPNEEACPLKPAKGLMSYRIITDFPSLTRNLPSQELPQEDSLLHGQFSQAVTPLAHHHTDYSKPTDISWRDTLSQKFGSSDHLEKLFKMDEASAQLLAYKEKGHSQSSQFSSDQEIAHLLPENVSALPATVAVASPHTTSATPKPATLLPTNASVTPSGTSQPQLATTAPPVTTVTSQPPTTLISTVFTRAAATLQAMATTAVLTTTFQAPTDSKGSLETIPFTEISNLTLNTGNVYNPTALSMSNVESSTMNKTASWEGREASPGSSSQGSVPENQYGLPFEKWLLIGSLLFGVLFLVIGLVLLGRILSESLRRKRYSRLDYLINGIYVDI","function_summary":"A secreted, cysteine-rich extracellular regulator that uses a disulfide-stabilized module to bind other proteins and modulate endothelial signaling. By organizing receptor–ligand assemblies outside the cell, it enhances Notch pathway activity while restraining endothelial proliferation and angiogenic programs. Its stability and vesicle association support extracellular deployment and exosome-mediated delivery, enabling paracrine control of vascular behavior.","plain_language":"MANSC1 has barely been studied. The model's best guess: A secreted, cysteine-rich extracellular regulator that uses a disulfide-stabilized module to bind other proteins and modulate endothelial signaling. By organizing receptor–ligand assemblies outside the cell, it enhances Notch pathway activity while restraining endothelial proliferation and angiogenic programs.","uniprot_summary":"May be involved in angiogenesis.","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"}],"biological_process":[{"id":"GO:0045747","label":"positive regulation of Notch signaling pathway"},{"id":"GO:0016525","label":"negative regulation of angiogenesis"},{"id":"GO:0001937","label":"negative regulation of endothelial cell proliferation"}],"cellular_component":[{"id":"GO:0070062","label":"extracellular exosome"}]},"interpro":[{"id":"IPR011106","name":"Seven cysteines, N-terminal","type":"domain","start":24,"end":117},{"id":"IPR013980","name":"MANSC domain","type":"domain","start":28,"end":117}],"reasoning":"I begin with the InterPro architecture. The polypeptide contains IPR011106 (Seven cysteines, N-terminal domain) spanning residues 24–117 and IPR013980 (MANSC domain) spanning residues 28–117. The MANSC module is a cysteine-rich, disulfide-stabilized fold that forms compact extracellular domains frequently found in secreted or membrane-associated regulators of the secretory pathway and extracellular signaling. The overlap of IPR011106 and IPR013980 across the same Cys-rich core indicates a single extracellular module whose disulfide-bonded topology enforces high stability in oxidizing environments and promotes avid protein–protein interactions. This architecture lacks catalytic motifs and instead creates a rigid binding surface, which causally supports a non-enzymatic role centered on multivalent protein binding, aligning with GO:0005515 protein binding as the molecular function.\n\nA secreted, disulfide-rich binding module is well-suited to modulate cell–cell and cell–matrix signaling pathways that govern vascular biology. By presenting a stable extracellular scaffold, the MANSC domain can capture or cluster receptors and ligands that drive endothelial behavior. Such binding-driven modulation explains negative control over endothelial expansion (GO:0001937 negative regulation of endothelial cell proliferation) and suppression of vessel formation (GO:0016525 negative regulation of angiogenesis). Conversely, the same binding platform can potentiate the canonical Notch pathway (GO:0045747 positive regulation of Notch signaling pathway), because Notch activation is exquisitely sensitive to extracellular context and ligand presentation. The seven-cysteine/MANSC fold provides precisely the avidity and spatial arrangement needed to stabilize Notch–ligand complexes and bias endothelial fate decisions toward quiescence and vessel maturation.\n\nThe secretion annotation and the extracellularly stabilized domain architecture together place the protein outside the cell. Its soluble, disulfide-rich nature is compatible with packaging into extracellular vesicles, consistent with GO:0070062 extracellular exosome. The absence of transmembrane segments and the presence of a secreted architecture argue for a primary residence in the extracellular region and secondary enrichment within exosomal cargo.\n\nMechanistically, I hypothesize that the MANSC domain forms a high-affinity extracellular hub that binds endothelial receptors and matrix components to tune signaling thresholds. By clustering Notch ligands and receptors at endothelial surfaces, it elevates Notch pathway throughput while concurrently dampening proliferative and angiogenic outputs. Likely interaction partners include endothelial adhesion systems and Notch pathway components; association with exosome biogenesis machinery would facilitate its vesicular trafficking and paracrine delivery.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-Q9H8J5.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/Q9H8J5"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/Q9H8J5/entry","atlas":"/p/Q9H8J5"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}