Author:
Klassen R. Bryan,Crenshaw Kimberly,Kozyraki Renata,Verroust Pierre J.,Tio Laura,Atrian Sílvia,Allen Patricia L.,Hammond Timothy G.
Abstract
Although several heavy metal toxins are delivered to the kidney on the carrier protein metallothionein (MT), uncertainty as to how MT enters proximal tubular cells limits treatment strategies. Prompted by reports that MT-I interferes with renal uptake of the megalin ligand β2-microglobulin in conscious rats, we tested the hypothesis that megalin binds MT and mediates its uptake. Three lines of evidence suggest that binding of MT to megalin is critical in renal proximal tubular uptake of MT-bound heavy metals. First, MT binds megalin, but not cubilin, in direct surface plasmon resonance studies. Binding of MT occurs at a single site with a Kd∼10−4and, as with other megalin ligands, depends on divalent cations. Second, antisera and various known megalin ligands inhibit the uptake of fluorescently labeled MT in model cell systems. Anti-megalin antisera, but not control sera, displace >90% bound MT from rat renal brush-border membranes. Megalin ligands including β2-microglobulin and also recombinant MT fragments compete for uptake by megalin-expressing rat yolk sac BN-16 cells. Third, megalin and fluorescently labeled MT colocalize in BN-16 cells, as shown by fluorescent microscopic techniques. Follow-up surface plasmon resonance and flow cytometry studies using overlapping MT peptides and recombinant MT fragments identify the hinge SCKKSCC region of MT as a critical site for megalin binding. These findings suggest that disruption of the SCKKSCC motif can inhibit proximal tubular MT uptake and thereby eliminate much of the renal accumulation and toxicity of heavy metals such as cadmium, gold, copper, and cisplatinum.
Publisher
American Physiological Society
Reference50 articles.
1. Agency for Toxic Substances and Disease Registry.Toxicological Profile for Cadmium. Atlanta, GA: US Department of Health and Human Services, Public Health Service, 1999.
2. Atrian S, Bofill R, Capdevila M, Cols N, Gonzalez-Duarte P, Gonzalez-Duarte R, Leiva A, Palacios O, and Romero-Isart N.Recombinant synthesis and metal-binding abilities of mouse metallothionein 1 and its α- and β-domains. In:Metallothionein IV, edited by Klaassen CD. Basel: Birkhäuser Verlag, 1999, p. 55–61.
3. Light-chain binding sites on renal brush-border membranes
4. The renal uptake of proteins: A nonselective process in conscious rats
5. The effects of low doses of cadmium-metallothionein on the renal uptake of β2-microglobulin in rats
Cited by
120 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献