A two-receptor pathway for catabolism of Clara cell secretory protein in the kidney

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Item Type:	Article
Title:	A two-receptor pathway for catabolism of Clara cell secretory protein in the kidney
Creators Name:	Burmeister, R., Boe, I.M., Nykjaer, A., Jacobsen, C., Moestrup, S.K., Verroust, P., Christensen, E.I., Lund, J. and Willnow, T.E.
Abstract:	Clara cell secretory protein (CCSP) is a transport protein for lipophilic substances in bronchio-alveolar fluid, plasma, and uterine secretion. It acts as a carrier for steroid hormones and polychlorinated biphenyl metabolites. Previously, the existence of receptors for uptake of CCSP-ligand complexes into the renal proximal tubules had been suggested. Using surface plasmon resonance analysis, we demonstrate that CCSP binds to cubilin, a peripheral membrane protein on the surface of proximal tubular cells. Binding to cubilin results in uptake and lysosomal degradation of CCSP in cultured cells. Surprisingly, internalization of CCSP is blocked not only by cubilin antagonists but also by antibodies directed against megalin, an endocytic receptor that does not bind CCSP but associates with cubilin. Consistent with a role of both receptors in renal uptake of CCSP in vivo, patients deficient for cubilin or mice lacking megalin exhibit a defect in tubular uptake of the protein and excrete CCSP into the urine. These findings identify a cellular pathway consisting of a CCSP-binding protein (cubilin) and an endocytic coreceptor (megalin) responsible for tissue-specific uptake of CCSP and associated ligands.
Keywords:	Biological Transport, Biosensing Techniques, Cell Membrane, Cell Surface Receptors, Edetic Acid, Fanconi Syndrome, Heymann Nephritis Antigenic Complex, Kidney, Kinetics, Knockout Mice, Membrane Glycoproteins, Multiple Myeloma, Protein Binding, Proteins, Proximal Kidney Tubules, Recombinant Proteins, Surface Plasmon Resonance, Uteroglobin, Animals, Mice, Rats
Source:	Journal of Biological Chemistry
ISSN:	0021-9258
Publisher:	American Society for Biochemistry and Molecular Biology
Volume:	276
Number:	16
Page Range:	13295-13301
Date:	1 January 2001
Official Publication:	https://doi.org/10.1074/jbc.m010679200
PubMed:	View item in PubMed

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