Cubilin

Cubilin is a protein that in humans is encoded by the CUBN gene. 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 complexes, enabling endocytosis of complexes by means of amnionless.

Biochemistry

Cubilinis essentially only present in the small intestine and kidneys.
A complex of amnionless and cubilin forms the cubam receptor.

Clinical significance

Mutations in CUBN may play a role in autosomal recessive megaloblastic anemia.
Cubilin is a potential diagnostic and prognostic cancer biomarker for kidney cancer. Based on patient survival data, high levels of cubilin in tumor cells is a favourable prognostic biomarker in renal cell carcinoma.