Endogenous transport systems in the Xenopus Laevis oocyte plasma membrane

Sobczak Katja, Bangel-Ruland Nadine, Leier Geraldine, Weber Wolf-Michael

Abstract

Oocytes of the South African clawed frog Xenopus laevis are widely used as a heterologous expression systemfor the characterization of transport systems such as passive and active membrane transporters,receptors and a whole plethora of other membrane proteins originally derived from animal or plant tissues.The large size of the oocytes and the high degree of expression of exogenous mRNA or cDNA makesthem an optimal tool, when compared with other expression systems such as yeast, Escherichia coli oreukaryotic cell lines, for the expression and functional characterization of membrane proteins. This easyto handle expression system is becoming increasingly attractive for pharmacological research. Commerciallyavailable automated systems that microinject mRNA into the oocytes and perform electrophysiologicalmeasurements fully automatically allow for a mass screening of new computer designed drugsto target membrane transport proteins. Yet, the oocytes possess a large variety of endogenous membranetransporters and it is absolutely mandatory to distinguish the endogenous transporters from the heterologous,expressed transport systems. Here, we review briefly the endogenous membrane transport systemsof the oocytes.