Transport activity of MCT1 expressed in Xenopus oocytes is increased by interaction with carbonic anhydrase
Holger M Becker1, Daniela Hirnet, Claudia Fecher-Trost
1Abteilungen, Allgemeine Zoologie, Fachbereich Biologie, Technische Universität Kaiserslautern, D-67653 Kaiserslautern, Germany.
Abstract:
Injection of carbonic anhydrase isoform II (CA) into Xenopus frog oocytes increased the rate of H+ flux via the rat monocarboxylate transporter isoform 1 (MCT1) expressed in the oocytes. MCT1 activity was assessed by changes of intracellular H+ concentration measured by pH-selective microelectrodes during application of lactate. CA-induced augmentation of the rate of H+ flux mediated by MCT1 was not inhibited by ethoxyzolamide (10 microM) and did not depend on the presence of added CO2/HCO3- but was suppressed by injection of an antibody against CA. Deleting the C terminus of the MCT1 greatly reduced its transport rate and removed transport facilitation by CA. Injected CA accelerated the CO2/HCO3(-)-induced acidification severalfold, which was blocked by ethoxyzolamide and was independent of MCT1 expression. Mass spectrometry confirmed activity of CA as injected into the frog oocytes. With pulldown assays we demonstrated a specific binding of CA to MCT1 that was not attributed to the C terminus of MCT1. Our results suggest that CA enhances MCT1 transport activity, independent of its enzymatic reaction center, presumably by binding to MCT1.
Related Concept Videos
Active Transport
Primary active transporters, like Na+, K+ and -ATPase, directly utilize ATP to move ions across the membrane. These transporters play significant roles in various physiological processes. For instance, Na+, K+ and -ATPase maintain...
Transcellular Transport of Solutes
Carrier-Mediated Transport
Active transport involves two types of membrane-spanning transporters: uptake and efflux. Uptake transporters are expressed in the small...
Secondary Active Transport
Secondary Active Transport
The ADP/ATP Carrier Protein


