Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

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Castillo, G. et al.

A homologue of the mammalian multidrug resistance gene (mdr) is functionally expressed in the intestine of Xenopus laevis.

P-glycoprotein is an integral membrane protein that functions in multidrug resistance ( MDR) cells as a drug efflux pump to maintain intracellular concentrations of antitumor drugs below cytotoxic levels. A homologue of the mammalian mdr gene has been isolated and characterized from Xenopus laevis (Xe- mdr). The cDNA was isolated from a tadpole cDNA library using the full length mouse mdrlb cDNA as a probe. The Xe- mdr encodes a protein that is 66% identical to the mouse mdrlb and 68% identical to the human mdrl. The predicted structure of the Xe- mdr gene product identifies twelve membrane spanning domains and two ATP binding sites both of which are the hallmark of the ABC (ATP binding cassette) transporters. Xe- mdr mRNA is expressed as a single message of 4.5 kb and is found predominantly in the intestine. Xe- mdr message is increased 3- to 4-fold in the ileum compared to the rest of the small intestine. In situ hybridization of sequential sections from the small intestine localized the expression of the Xe- mdr to the cells lining the lumenal epithelium. Brush border membrane vesicles prepared from the small intestine of Xenopus laevis effluxed vinblastine in an ATP-dependent manner. Efflux was decreased by verapamil, a known inhibitor of P-glycoprotein function. These studies indicate that the structure of Xe- mdr has been conserved and suggest that the protein has a role in maintaining the function of the normal intestine in Xenopus.[1]

References

A homologue of the mammalian multidrug resistance gene (mdr) is functionally expressed in the intestine of Xenopus laevis. Castillo, G., Shen, H.J., Horwitz, S.B. Biochim. Biophys. Acta (1995) [Pubmed]

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