Red Cell Transporters and Channels

The Red Blood Cell (RBC) plasma membrane contains integral membrane proteins allowing the diffusion of molecules between the plasma and the RBCs. A fine regulation of these exchanges is crucial for maintaining homeostasis of the intracellular pH (pHi) and the water content in response to physiological variations, and plays a major role in membrane mechanical properties and membrane biogenesis.

Abnormalities in expression and function of RBC transporters and channels are involved in many pathologies including either membrane pathologies associated with hemolytic anemia (Rhesus (Rh) deficiencies, hereditary stomatocytosis,…) or parasitical (malaria) and bacterial infections.

In our team, we carry out several biophysical and biochemical studies under physiological and pathological conditions to investigate the function of RBC transporters and channels, together with the analysis of transport regulation by protein assembly into multimolecular complexes within the red cell membranes.

In the past, we developed methods using specific fluorescent probes and the stopped-flow spectrofluorometry adapted to the rapid kinetics of both the chloride/bicarbonate exchange and the ammonia transport through two members of a same RBC membrane complex that modifies the pHi, the Anion Exchanger 1 (AE1 or Band 3) and the Rh proteins (RhAG), respectively. We showed a loss and a gain of ammonia transport in patients suffering from stomatocytosis associated with mutations in RhAG and in transgenic mice expressing human RhAG, respectively. We also highlighted altered chloride/bicarbonate exchange in patients suffering from stomatocytosis associated with mutations in AE1. Using these approaches, we finally identified the impact of membrane partners (such as stomatin) in the activity of AE1.

In parallel, we performed light scattering stopped-flow experiments to characterize the RBC water permeability through Aquaporin 1 (AQP1) and to study the urea transporter (UT-B). We showed a major role of these channels in regulatory processes of the RBC volume and described an impairment of water movements in known genetic variants, AQPnull and UT-Bnull.

Today, our studies are focused on two mechanosensitive channels (Piezzo1 and Pannexin 1), the cholesterol translocator protein (TSPO) and the voltage dependent anion channel (VDAC).

In parallel, we investigate RBC membrane complexes using SMALPs, a novel detergent-free strategy that allows the production of nanodics containing membrane proteins and their surrounding lipids in a native state.

To further these goals, we also established international collaborations with several laboratories from Germany, Uruguay and Argentina, and promoted crossing internships for PhD students, technicians and researchers among our countries.

Working together with research groups in Uruguay, we are studying the impact of aquaporins and other RBC channels regulating the oxidative stress.

We established a recent collaboration with Pr Kaestner's team at Saarland University (Germany) to study the regulation of calcium homeostasis in RBCs by the erythroid stomatin.

Finally, 5 years ago, we created a research network with teams from several Argentinian Universities, in order to study the impact of exogenous peptides from hemolytic bacteria strains in the RBC membrane function and the ATP release from RBCs.