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Functional expression of intrinsic factor-cobalamin receptor by renal proximal tubular epithelial cells.
J Biol Chem. 1991 Jul 15; 266(20):13135-40.JB

Abstract

Previous studies from our laboratory (Seetharam, B., Levine, J. S., Ramasamy, M., and Alpers, D. H. (1988) J. Biol. Chem. 263, 4443-4449; Fyfe, J. C., Ramanujam, K. S., Ramaswamy, K., Patterson, D. F., and Seetharam, B. (1991) J. Biol. Chem. 266, 4489-4494) have identified and isolated a 230-kDa receptor from rat and canine kidney which binds with high affinity [57Co]cyanocobalamin (Cbl) complexed to gastric intrinsic factor (IF). Although these studies have identified a renal receptor which binds intrinsic factor-cobalamin (IFCR), it is not known whether the binding is specific for IF-Cbl and whether renal cells internalize [57Co]Cbl bound to IF and transport [57Co]Cbl across the cell. Using a variety of renal cells, our results show that IF-[57Co]Cbl binding activity is detected in proximal tubular-derived epithelial cells from opossum (OK) and porcine kidney (LLC-PK1) but not in distal tubular-derived cells from canine kidney cells (MDCK). Metabolic labeling studies with Tran 35S-label confirmed the presence of a 230-kDa IFCR in OK and LLC-PK1 cells. Cell surface labeling and binding studies demonstrated that IFCR is targeted to the apical membrane. This apical expression of IFCR in OK cells is inhibited by the microtubule-disruptive drugs, colchicine and nocodazole. Opossum kidney cells when grown on culture inserts are polarized and transport [57Co]Cbl only when bound to IF and not to other Cbl binders. Furthermore, the transport of [57Co]Cbl occurred unidirectionally from the apical to the basolateral surface. Treatment of cells with colchicine or nocodazole inhibited the surface binding of IF-[57Co]Cbl as well as the transcytosis of [57Co]Cbl by 70-75%. IFCR retained intracellualarly by incubation of cells with colchicine or nocodazole is degraded by leupeptin-sensitive proteases. Based on these results, we suggest that proximal tubular-derived epithelial cells transport [57Co]Cbl bound to IF in a saturable way via receptor-mediated endocytosis.

Authors+Show Affiliations

Department of Medicine Division of Gastroenterology, Medical College of Wisconsin, Milwaukee 53226.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

1649178

Citation

Ramanujam, K S., et al. "Functional Expression of Intrinsic Factor-cobalamin Receptor By Renal Proximal Tubular Epithelial Cells." The Journal of Biological Chemistry, vol. 266, no. 20, 1991, pp. 13135-40.
Ramanujam KS, Seetharam S, Dahms NM, et al. Functional expression of intrinsic factor-cobalamin receptor by renal proximal tubular epithelial cells. J Biol Chem. 1991;266(20):13135-40.
Ramanujam, K. S., Seetharam, S., Dahms, N. M., & Seetharam, B. (1991). Functional expression of intrinsic factor-cobalamin receptor by renal proximal tubular epithelial cells. The Journal of Biological Chemistry, 266(20), 13135-40.
Ramanujam KS, et al. Functional Expression of Intrinsic Factor-cobalamin Receptor By Renal Proximal Tubular Epithelial Cells. J Biol Chem. 1991 Jul 15;266(20):13135-40. PubMed PMID: 1649178.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Functional expression of intrinsic factor-cobalamin receptor by renal proximal tubular epithelial cells. AU - Ramanujam,K S, AU - Seetharam,S, AU - Dahms,N M, AU - Seetharam,B, PY - 1991/7/15/pubmed PY - 1991/7/15/medline PY - 1991/7/15/entrez SP - 13135 EP - 40 JF - The Journal of biological chemistry JO - J Biol Chem VL - 266 IS - 20 N2 - Previous studies from our laboratory (Seetharam, B., Levine, J. S., Ramasamy, M., and Alpers, D. H. (1988) J. Biol. Chem. 263, 4443-4449; Fyfe, J. C., Ramanujam, K. S., Ramaswamy, K., Patterson, D. F., and Seetharam, B. (1991) J. Biol. Chem. 266, 4489-4494) have identified and isolated a 230-kDa receptor from rat and canine kidney which binds with high affinity [57Co]cyanocobalamin (Cbl) complexed to gastric intrinsic factor (IF). Although these studies have identified a renal receptor which binds intrinsic factor-cobalamin (IFCR), it is not known whether the binding is specific for IF-Cbl and whether renal cells internalize [57Co]Cbl bound to IF and transport [57Co]Cbl across the cell. Using a variety of renal cells, our results show that IF-[57Co]Cbl binding activity is detected in proximal tubular-derived epithelial cells from opossum (OK) and porcine kidney (LLC-PK1) but not in distal tubular-derived cells from canine kidney cells (MDCK). Metabolic labeling studies with Tran 35S-label confirmed the presence of a 230-kDa IFCR in OK and LLC-PK1 cells. Cell surface labeling and binding studies demonstrated that IFCR is targeted to the apical membrane. This apical expression of IFCR in OK cells is inhibited by the microtubule-disruptive drugs, colchicine and nocodazole. Opossum kidney cells when grown on culture inserts are polarized and transport [57Co]Cbl only when bound to IF and not to other Cbl binders. Furthermore, the transport of [57Co]Cbl occurred unidirectionally from the apical to the basolateral surface. Treatment of cells with colchicine or nocodazole inhibited the surface binding of IF-[57Co]Cbl as well as the transcytosis of [57Co]Cbl by 70-75%. IFCR retained intracellualarly by incubation of cells with colchicine or nocodazole is degraded by leupeptin-sensitive proteases. Based on these results, we suggest that proximal tubular-derived epithelial cells transport [57Co]Cbl bound to IF in a saturable way via receptor-mediated endocytosis. SN - 0021-9258 UR - https://www.unboundmedicine.com/medline/citation/1649178/Functional_expression_of_intrinsic_factor_cobalamin_receptor_by_renal_proximal_tubular_epithelial_cells_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0021-9258(18)98815-0 DB - PRIME DP - Unbound Medicine ER -