Research groups

Research

The bicarbonate transporter protein family: trafficking and molecular interactions in health and disease.

The bicarbonate transporter superfamily (SLC4) contains 10 members. These proteins are important for many physiological processes, including CO₂ transport in the blood, maintenance of intracellular pH and the secretion of acid-base equivalents. I have a particular interest in Anion exchanger 1 (AE1, SLC4A1), the founding member of the bicarbonate transporter family and a protein that is important for bicarbonate transport in blood and kidney.

AE1 forms the core of a complex of peripheral and integral membrane proteins in the Red Blood Cell (RBC) membrane, called the AE1 macrocomplex. This macrocomplex is disrupted in human haemolytic disease, infection (e.g. malaria) and in RBC aging. We are using a variety of cell expression systems to investigate the function, assembly, trafficking and molecular interactions of AE1 macrocomplex proteins in the developing and mature RBC. Once we know how this macrocomplex is assembled and how it functions at the red blood cell surface, we hope to utilise this knowledge to improve the oxygen carrying capacity and the survival rates of transfused blood. This work is conducted in collaboration with Prof. Dave Anstee’s group in the International Blood Group Laboratory at Bristol.

Confocal imaging of non-polarized MDCK cells stably expressing kAE1 to the plasma membrane (left) and the mistargeted dRTA mutants R589H (center) and R901Stop (right).

 

A truncated form of AE1, kAE1, is located in the basolateral membrane of the α-intercalated cells of the kidney. A number of AE1 gene mutations cause dominant and recessive forms of distal renal tubular acidosis (dRTA). It is becoming apparent that these dRTA mutations result in renal specific disease by altering the trafficking of kAE1 in the kidney. I have developed polarizable stable kidney cell lines that express human kAE1 and kAE1 mutants. By investigating the regions of kAE1 affected by dRTA mutations in these stable cell lines, we are providing valuable insights into how multi-spanning membrane proteins are delivered to the correct membrane in polarized cells and how the mis-trafficking of membrane proteins can cause human disease. In addition to kAE1, we are also developing stable cell lines expressing other bicarbonate transporter family members.

Group

Alice Brown, Roz Williamson, Tim Satchwell, Emile Van den Akker (NHSBT) and Steph Pellegrin (NHSBT).

Recent publications

Williamson RC, A Brown, Mawby WJ and Toye A.M. (2008) Human kidney anion exchanger 1 localisation in MDCK cells is controlled by the phosphorylation status of two critical tyrosines. Journal Cell Science. doi: 10.1242/jcs.035584 ePress.

Toye A.M., Williamson RC, Khanfar M, Bader-Meunier B, Cynober T, Thibault M, Tchernia G, Déchaux M, Delaunay J and Bruce LJ. (2008) Band 3 Courcouronnes (Ser667Phe): a trafficking mutant differentially rescued by wild type band 3 and glycophorin A. Blood. 2008 111:5380-9.

Toye A.M., Parker M.D., Daly C.M., Lu J., Virkki L.V., Pelletier M.F. and Boron W.F. (2006) The human NBCe1-A mutant R881C, associated with proximal renal tubular acidosis, retains function but is mistargeted in polarized renal epithelia. American Journal of  Physiology - Cell Physiology 291 C788-801.

Toye, AM, Ghosh S, Young MT, Jones G, Ramaugé M, Philippe L, Basu J, Delaunay J and M J.A. Tanner. (2005) Protein 4.2 association with band 3 (AE1, SLCA4) in Xenopus oocytes: effects of three natural protein 4.2 mutations associated with hemolytic anemia. Blood 105 4088-95.