Function and Dysfunction of Renal Transport Molecules: Lessons from Electrophysiology

Abstract

The availability of cloned transport molecules achieved by efforts in expression cloning has allowed their electrophysiological analysis in the Xenopus oocyte expression system. We describe the electrogenic uptake of various substrates by their corresponding transport molecules originally expressed in brush border membranes of proximal tubules. The functional properties of the following transport molecules are discussed: the sodium-coupled glucose transporter, the sodium-coupled phosphate transporter, the sodium-coupled sulfate transporter and the sodium-independent transporter of neutral and dibasic amino acids. Additionally, functional consequences of naturally occurring disease-causing mutations in some of these transport molecules are described.

Elaboration of a novel technique for purification of plasma membranes from Xenopus laevis oocytes

“…More particularly, the use of oocytes has been extremely fruitful in expression cloning of channels and transporters, taking advantage of sensitive techniques such as electrophysiology and radiotracer uptake (6,12,16,20). Rapidly, the use of oocytes has expanded to include physiological and biochemical characterization of heterologous proteins, which often led to the identification of pathological mechanisms associated with naturally occurring mutations.…”