Molecular mechanisms of transport, small ligand modulation, and subunit interaction of chloride transporting CLC proteins involved in human genetic diseases

The kidneys filter more than 1 kg of salt (NaCl) every day of which normally more than 99% is reabsorbed in the kidney tubules. CLC-Kb is a chloride ion channel involved in this process and mutations of it lead to a severe salt loss, called Bartter syndrome. We previously identified a novel mechanism of regulation of this channel by calcium ions and by protons. We intend to clarify in detail the mechanisms underlying this regulation, which is of physiological relevance and we hope will help to develop novel strategies for a treatment of Bartter syndrome. Another important function of the kidney is to reabsorb small proteins (e.g. albumin) that enter the kidney tubules. CLC-5 is necessary for the endocytosis and thus reabsorption of these proteins and CLC-5 mutations cause Dent disease a kidney stone disease, which is characterized by the massive loss of small proteins in the urine. We found previously that CLC-5 is not a chloride channel (as thought initially) but a chloride/proton antiporter. We intend to study the molecular mechanisms of function of this membrane protein using biophysical methods. Such knowledge will be helpful to better understand the precise role of CLC-5, why mutations of it cause disease, and to develop strategies for the treatment of Dent disease. A third aspect of this project regards a genetic disease associated with hydrocephaly (megalencephalic leukoencephalopathy with subcortical cysts, MLC). Very recently we discovered that the chloride channel CLC-2 interacts with GlialCAM, one of the genes mutated in MLC. We intend to investigate the molecular details of this novel interaction. Since little is known about the mechanisms that lead to MLC, our results are highly relevant for a better understanding of this rare disease. Overall, we hope that the specific expertise of our group in the field of CLC proteins will help to increase our knowledge on disparate diseases in which various members of the CLC family are involved.