Abstract
The mammalian Na+/H+ exchanger isoform 1 (NHE1) is a plasma membrane protein ubiquitously present in humans. It regulates intracellular pH by removing an intracellular proton in exchange for an extracellular sodium. It consists of a 500 amino acid membrane domain plus a 315 amino acid, regulatory cytosolic tail. Here, we investigated the effect of mutation of two amino acids of the regulatory tail, Ser785 and Ser787, that were similar in location and context to two amino acids of the Arabidopsis Na+/H+ exchanger SOS1. Mutation of these two amino acids to either Ala or phosphomimetic Glu did not affect surface targeting but led to a slight reduction in the level of protein expressed. The activity of the NHE1 protein was reduced in the phosphomimetic mutations and the effect was due to a decrease in Vmax activity. The Ser to Glu mutations also caused a change in the apparent molecular weight of both the full-length protein and of the cytosolic tail of NHE1. A conformational change in this region was indicated by differential trypsin sensitivity. We also found that a peptide containing amino acids 783–790 bound to several more proximal regions of the NHE1 tail in in vitro protein interaction experiments. The results are the first characterization of these two amino acids and show that they have significant effects on enzyme kinetics and the structure of the NHE1 protein.
Highlights
The mammalian Na+/H+ exchanger (NHE1) is a ubiquitously expressed membrane protein of human cells
We investigated the effect of mutation of two amino acids of the regulatory tail, Ser785 and Ser787, that were similar in location and context to two amino acids of the Arabidopsis Na+/H+ exchanger SOS1
Na+/H+ exchanger isoform 1 (NHE1) is important in breast cancer, where it acts as a trigger for metastasis [18,19,20]
Summary
The mammalian Na+/H+ exchanger (NHE1) is a ubiquitously expressed membrane protein of human cells. It removes a single intracellular proton in exchange for one extracellular sodium ion. NHE1 is the ubiquitous plasma membrane isoform in mammals with several important physiological functions [3,4,5,9,10,11,12]. Again, elevated activity of the protein promotes the disease, and phosphorylation at a specific amino acid in the tail is suggested to be a critical trigger enhancing NHE1 activity and promoting the disease [21,22]. It seems clear that regulation of the NHE1 at its cytosolic tail is important in its function and human disease. While direct inhibition of NHE1 has been suggested to treat human disease, there have been detrimental off-target side effects of NHE1 inhibitors in at least one clinical trial [23] and modification of NHE1 through its regulation has been suggested to be one approach for the treatment of human disease [24]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
