The Homo sapiens Na+/H+ antiporter NHA2 (SLC9B2) transports Na+ or Li+ in exchange for protons across cell membranes, and its dysfunction results in various pathologies. The activity of HsNHA2 is specifically inhibited by the flavonoid phloretin. Using bioinformatic modeling, we predicted two amino acids (R177 and S178) as being important for the binding of phloretin to the HsNHA2 molecule. Functional expression of HsNHA2 in Saccharomyces cerevisiae and its site-directed mutagenesis revealed that while the R177T mutation resulted in an antiporter that was less sensitive to phloretin, the S178T mutation enhanced the inhibitory effect of phloretin on HsNHA2. Our data corroborate the transport properties of HsNHA2 and its interactions with an inhibitor and can be helpful for the development of new therapeutics targeting this antiporter and its pleiotropic physiological functions.

• Klíčová slova
• Na+/H+ antiporter, human NHA2, phloretin inhibition, yeast,
• MeSH
• floretin * farmakologie   chemie   metabolismus   MeSH
• lidé MeSH
• molekulární modely MeSH
• mutageneze cílená MeSH
• Na(+)-H(+) antiport * genetika   antagonisté a inhibitory   chemie   metabolismus   MeSH
• Saccharomyces cerevisiae genetika   metabolismus   MeSH
• sekvence aminokyselin MeSH
• vazba proteinů MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• floretin * MeSH
• Na(+)-H(+) antiport * MeSH

The alteration of the fine-tuned balance of phospho/dephosphorylation reactions in the cell often results in functional disturbance. In the yeast Saccharomyces cerevisiae, the overexpression of Ser/Thr phosphatase Ppz1 drastically blocks cell proliferation, with a profound change in the transcriptomic and phosphoproteomic profiles. While the deleterious effect on growth likely derives from the alteration of multiple targets, the precise mechanisms are still obscure. Ppz1 is a negative effector of potassium influx. However, we show that the toxic effect of Ppz1 overexpression is unrelated to the Trk1/2 high-affinity potassium importers. Cells overexpressing Ppz1 exhibit decreased K+ content, increased cytosolic acidification, and fail to properly acidify the medium. These effects, as well as the growth defect, are counteracted by the deletion of NHA1 gene, which encodes a plasma membrane Na+, K+/H+ antiporter. The beneficial effect of a lack of Nha1 on the growth vanishes as the pH of the medium approaches neutrality, is not eliminated by the expression of two non-functional Nha1 variants (D145N or D177N), and is exacerbated by a hyperactive Nha1 version (S481A). All our results show that high levels of Ppz1 overactivate Nha1, leading to an excessive entry of H+ and efflux of K+, which is detrimental for growth.

• Klíčová slova
• K+ transport, Nha1, Ppz1 phosphatase, Saccharomyces cerevisiae, cation homeostasis, intracellular pH,
• Publikační typ
• časopisecké články MeSH