title: Characterization of chicken cystatin binding to rat renal brush-border membranes.
abstract: Chicken cystatin, a homologue of human cystatin C, like other low-molecular-weight proteins is metabolized by renal proximal tubule cells. However, the precise mechanism(s) of this process has not been elucidated yet. To characterize chicken cystatin binding to renal brush-border membranes, the incubation of fluorescein labelled protein with rat cortical homogenate was performed. Saturation-dependent and reversible binding with low affinity (K(d)=3.67-4.07 microM) and high capacity (B(max)=2.32-2.79 nmol/mg) was observed. Bovine albumin was the most potent competitor (K(i)=0.7 microM) among other megalin/cubilin ligands tested. The presence of Ca(+2) ions was necessary to effective cystatin binding by brush-border membranes. Obtained data strongly support the hypothesis that chicken cystatin is a novel ligand for megalin/cubilin receptors tandem on proximal tubular cells.
authors.affiliation: Department of Pharmaceutical Biochemistry, Wrocław Medical University, Szewska 38/39, 50-139 Wrocław, Poland.
authors.forename: Bogusława
authors.initials: B
authors.lastname: Konopska
authors.forename: Jakub
authors.initials: J
authors.lastname: Gburek
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Gołab
authors.forename: Maria
authors.initials: M
authors.lastname: Warwas
mesh_terms: D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002478:Cells, Cultured; D002642:Chick Embryo; D015891:Cystatins / Q000737:chemistry / Q000378:metabolism*; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D007672:Kidney Cortex / Q000166:cytology* / Q000187:drug effects; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D026561:Low Density Lipoprotein Receptor-Related Protein-2 / Q000378:metabolism; D008297:Male; D008871:Microvilli / Q000378:metabolism*; D008970:Molecular Weight; D051381:Rats; D011915:Rats, Inbred BUF; D011956:Receptors, Cell Surface / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000378:metabolism / Q000494:pharmacology
chemical_list: D015891:Cystatins; D026561:Low Density Lipoprotein Receptor-Related Protein-2; D011956:Receptors, Cell Surface; C100158:cystatin, egg-white; C029486:intrinsic factor-cobalamin receptor; D012710:Serum Albumin, Bovine; D016650:Fluorescein-5-isothiocyanate; D002118:Calcium