Cubilin

Cubilin is a protein that in humans is encoded by the CUBN gene.^[5][6][7] It is present upon the luminal surface of enterocytes of the ileum where it facilitates absorption of vitamin B12 by acting as a receptor for IF-cobalamin (intrinsic factor - vitamin B12) complexes, enabling endocytosis of complexes by means of amnionless (AMN).^[8][9]

CUBN
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 3KQ4
Identifiers
Aliases	CUBN, IFCR, MGA1, gp280, cubilin, IGS, IGS1
External IDs	OMIM: 602997; MGI: 1931256; HomoloGene: 37434; GeneCards: CUBN; OMA:CUBN - orthologs
Gene location (Human) Chr. Chromosome 10 (human)[1] Band 10p13 Start 16,823,966 bp[1] End 17,129,811 bp[1]
Gene location (Mouse) Chr. Chromosome 2 (mouse)[2] Band 2 A1|2 9.86 cM Start 13,281,149 bp[2] End 13,496,624 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in kidney tubule glomerulus renal medulla metanephric glomerulus sperm oocyte right uterine tube human kidney gonad secondary oocyte Top expressed in primitive streak yolk sac ileum human kidney epithelium of small intestine intestinal villus jejunum epithelium of lens Ileal epithelium right kidney More reference expression data BioGPS More reference expression data
Gene ontology Molecular function calcium ion binding protein homodimerization activity protein binding transporter activity cobalamin binding metal ion binding channel regulator activity hemoglobin binding signaling receptor activity cargo receptor activity Cellular component brush border extrinsic component of external side of plasma membrane endoplasmic reticulum clathrin-coated pit lysosomal membrane cytoplasm Golgi apparatus endosome apical part of cell lysosome lysosomal lumen membrane cytosol extracellular exosome endocytic vesicle endosome membrane plasma membrane apical plasma membrane brush border membrane Golgi-associated vesicle ionotropic glutamate receptor complex coated vesicle endocytic vesicle membrane neuron projection membrane synapse Biological process tissue homeostasis cobalamin transport lipid metabolism protein transport cholesterol metabolic process vitamin D metabolic process cobalamin metabolic process steroid metabolic process endocytosis lipoprotein transport receptor-mediated endocytosis high-density lipoprotein particle clearance transport in utero embryonic development thigmotaxis hyperosmotic response response to nutrient adult locomotory behavior response to bacterium endocytic hemoglobin import into cell regulation of locomotion cobalamin catabolic process positive regulation of synaptic transmission, glutamatergic protein homotrimerization Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 8029 65969 Ensembl ENSG00000107611 ENSMUSG00000026726 UniProt O60494 Q9JLB4 RefSeq (mRNA) NM_001081 NM_001081084 RefSeq (protein) NP_001072 NP_001074553 Location (UCSC) Chr 10: 16.82 – 17.13 Mb Chr 2: 13.28 – 13.5 Mb PubMed search [3] [4]
Wikidata
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Biochemistry

Cubilinis essentially only present in the small intestine and kidneys.^[10]

A complex of amnionless and cubilin forms the cubam receptor.^{[citation needed]}

Clinical significance

Mutations in CUBN may play a role in autosomal recessive megaloblastic anemia.^[7]

Cubilin is a potential diagnostic and prognostic cancer biomarker for kidney cancer.^[11] Based on patient survival data, high levels of cubilin in tumor cells is a favourable prognostic biomarker in renal cell carcinoma.^[12][13]