REGULATION OF NHE1 · Investigations on the regulation of the sodium hydrogen exchanger isoform 1 by novel methods

Final Activity Report Summary - REGULATION OF NHE1 (Investigations on the regulation of the sodium hydrogen exchanger isoform 1 by novel methods)

Sodium-hydrogen exchangers (NHEs) are ubiquitous ion transport proteins which are present in bacteria, plants, fungi and animals. In mammals, including humans, NHE1 is the most widely expressed isoform, present on all cells. NHE1 is crucial for a wide variety of cellular processes, such as cell pH regulation, volume defence and cell growth. At the organism level, NHE1 is important in cancer biology, central nervous system integrity and cardiovascular pathophysiology. Tumour cells express high levels of NHE1, which enhances their potential for growth and metastasis. Currently, specific NHE1 inhibitors are being tested in humans within the setting of myocardial infarction, tumour growth, arterial hypertension and heart failure. NHE1 localises to the outer surface membrane of the cell, the so-called plasma membrane, extrudes protons from the cell interior and imports sodium in the cell. This causes cell alkalinisation, increased intracellular sodium concentration and, consequently, cell swelling. Cytoplasmic acidification and growth factors are the strongest activators of NHE1. In addition to the control of cell volume and pH, NHE1 regulates cell migration and mechanosensation, which in turn contribute significantly to the pathogenesis of cancer and cardiovascular disease in humans. Given the multiple biological functions of NHE1 it is clear that the amount of NHE1 at the cell plasma membrane and the turnover of NHE1 at the plasma membrane have to be tightly controlled. The goal of our project was to understand the molecular mechanisms controlling NHE1 protein abundance at the plasma membrane. During the two year project, we identified the key mechanism that controlled NHE1 at the plasma membrane. This involved a process called ubiquitylation. Ubiquitin is a small molecule that becomes attached to proteins and serves as a destiny tag for the cell. Ubiquitylated proteins can be degraded, taken away from the surface membrane or targeted to a new place within the cell. We identified key molecular players in this process for NHE1 through various molecular biological experiments in cell culture and analysed functional aspects with electrophysiology. Our findings significantly expanded the knowledge on NHE1 and would potentially influence drug development for the diseases mentioned above. Moreover, the results that were obtained by the end of the project were soon to be published in a peer-reviewed journal and become accessible to all researchers in the field and the general public.

Data: CORDIS, © European Union