Endocytic receptor which plays a role in lipoprotein, vitamin and iron metabolism by facilitating their uptake (PubMed:9572993, PubMed:10371504, PubMed:11717447, PubMed:11606717, PubMed:14576052). Acts together with LRP2 to mediate endocytosis of high-density lipoproteins, GC, hemoglobin, ALB, TF and SCGB1A1. Acts together with AMN to mediate endocytosis of the CBLIF-cobalamin complex (PubMed:9572993, PubMed:14576052). Binds to ALB, MB, Kappa and lambda-light chains, TF, hemoglobin, GC, SCGB1A1, APOA1, high density lipoprotein, and the CBLIF-cobalamin complex. Ligand binding requires calcium (PubMed:9572993). Serves as important transporter in several absorptive epithelia, including intestine, renal proximal tubules and embryonic yolk sac. May play an important role in the development of the peri-implantation embryo through internalization of APOA1 and cholesterol. Binds to LGALS3 at the maternal-fetal interface. Interacts with AMN (PubMed:14576052, PubMed:29402915, PubMed:20237569, PubMed:30523278). Component of the cubam complex composed of one CUBN trimer and one AMN chain (PubMed:30523278). The cubam complex can dimerize (By similarity). Interacts with LRP2 in a dual-receptor complex in a calcium-dependent manner. Found in a complex with PID1/PCLI1, LRP1 and CUBNI. Interacts with LRP1 and PID1/PCLI1. Lacks a transmembrane domain and depends on interaction with AMN for location at the plasma membrane (PubMed:29402915, PubMed:30523278). Colocalizes with AMN and LRP2 in the endocytotic apparatus of epithelial cells (By similarity). Detected in kidney cortex (at protein level) (PubMed:9572993). Expressed in kidney proximal tubule cells, placenta, visceral yolk-sac cells and in absorptive intestinal cells. Expressed in the epithelium of intestine and kidney. The CUB domains 5 to 8 mediate binding to CBLIF and ALB. CUB domains 1 and 2 mediate interaction with LRP2. The cubam complex is composed of a 400 Angstrom long stem and a globular crown region. The stem region is probably formed by AMN and the CUBN N-terminal region, including the EGF-like domains. The crown is probably formed by the CUBN CUB domains. The precursor is cleaved by a trans-Golgi proteinase furin, removing a propeptide. N-glycosylated. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry.