J Toxicol Sci 2010 Dec 01;356:827-34. doi: 10.2131/jts.35.827.

Ribosomal protein L3 mediated the transport of digoxin in Xenopus laevis oocyte.

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Ribosomal protein L3 (RPL3) is known to be an indispensable and essential component for the peptidyltransferase center. In the present study, we found a novel function of RPL3 using a Xenopus laevis oocyte expression system. When expressed in X. oocytes, RPL3 mediated the high affinity transport of [(3)H]digoxin (K(m) = 213.3 ± 46.8 nM) in a time-, concentration-, and sodium-dependent manners. The maximum velocity of the transport of [(3)H]digoxin via RPL3 produced at physiological pH. However, we did not observe RPL3-mediated transport of several organic solutes such as [(14)C]androstenedione, [(3)H]dexamethasone, [(3)H]dehydroepiandrosterone sulfate, [(3)H]L-tryptophan, [(14)C]L-ascorbic acid, [(14)C]α-ketoglutarate, [(14)C]glutarate, [(3)H]methotrexate, [(3)H]bumetanide, [(3)H]probenecid, [(14)C]salicylic acid, [(14)C]theophylline and [(3)H]valproate. Our results suggest that RPL3 functions as a drug carrier protein and may be involved in the digoxin toxicity in the human body.

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Species referenced: Xenopus laevis
Genes referenced: rpl3