CUBN is a multifunctional protein primarily known for its role in the absorption of various nutrients, including vitamin B12 and proteins such as albumin, from the intestinal tract and renal tubules. This large glycoprotein acts as a receptor, facilitating the endocytosis of ligands bound to its extracellular domains. In the kidney, CUBN works in concert with the endocytic receptor megalin to reabsorb filtered proteins and prevent their loss in urine, thereby maintaining protein homeostasis. Additionally, CUBN plays a critical role in the transportation of vitamin B12 across the intestinal epithelium, a process vital for normal cellular function and metabolism. Dysregulation...