Please use this identifier to cite or link to this item:
Title: An intracellular trafficking defect in type-I cystinuria rBAT mutants Met467Thr and Met467Lys
Author: Chillarón Chaves, José Julio
Estévez Povedano, Raúl
Samarzija, Ita
Waldegger, Siegfried
Testar, Xavier
Lang, Florian
Zorzano Olarte, Antonio
Busch, Andreas
Palacín Prieto, Manuel
Keywords: Aminoàcids
Proteïnes portadores
Amino acids
Carrier proteins
Issue Date: 4-Apr-1997
Publisher: American Society for Biochemistry and Molecular Biology
Abstract: The human rBAT protein elicits sodium-independent, high affinity obligatory exchange of cystine, dibasic amino acids, and some neutral amino acids in Xenopus oocytes (Chillarón, J., Estévez, R., Mora, C., Wagner, C. A., Suessbrich, H., Lang, F., Gelpí, J. L., Testar, X., Busch, A. E., Zorzano, A., and Palacín, M. (1996) J. Biol. Chem. 271, 17761-17770). Mutations in rBAT have been found to cause cystinuria (Calonge, M. J., Gasparini, P., Chillarón, J., Chillón, M., Galluci, M., Rousaud, F., Zelante, L., Testar, X., Dallapiccola, B., Di Silverio, F., Barceló, P., Estivill, X., Zorzano, A., Nunes, V., and Palacín, M. (1994) Nat. Genet. 6, 420-426). We have performed functional studies with the most common point mutation, M467T, and its relative, M467K, using the oocyte system. The Km and the voltage dependence for transport of the different substrates were the same in both M467T and wild type-injected oocytes. However, the time course of transport was delayed in the M467T mutant: maximal activity was accomplished 3-4 days later than in the wild type. This delay was cRNA dose-dependent: at cRNA levels below 0.5 ng the M467T failed to achieve the wild type transport level. The M467K mutant displayed a normal Km, but the Vmax was between 5 and 35% of the wild type. The amount of rBAT protein was similar in normal and mutant-injected oocytes. In contrast to the wild type, the mutant proteins remained endoglycosidase H-sensitive, suggesting a longer residence time in the endoplasmic reticulum. We quantified the amount of rBAT protein in the plasma membrane by surface labeling with biotin 2 and 6 days after injection. Most of the M467T and M467K protein was located in an intracellular compartment. The converse situation was found in the wild type. Despite the low amount of M467T protein reaching the plasma membrane, the transport activity at 6 days was the same as in the wild type-injected oocytes. The increase in plasma membrane rBAT protein between 2 and 6 days was completely dissociated from the rise in transport activity. These data indicate impaired maturation and transport to the plasma membrane of the M467T and M467K mutant, and suggest that rBAT alone is unable to support the transport function.
Note: Reproducció del document publicat a:
It is part of: Journal of Biological Chemistry, 1997, vol. 272, num. 14, p. 9543-9549
Related resource:
ISSN: 0021-9258
Appears in Collections:Articles publicats en revistes (Ciències Fisiològiques)
Articles publicats en revistes (Bioquímica i Biomedicina Molecular)
Articles publicats en revistes (Biologia Cel·lular, Fisiologia i Immunologia)

Files in This Item:
File Description SizeFormat 
114267.pdf531.43 kBAdobe PDFView/Open

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.