This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Yenush, L. Articles by Serrano, R. Search for Related Content PubMed PubMed Citation Articles by Yenush, L. Articles by Serrano, R.

 Previous Article  |  Next Article 

Molecular and Cellular Biology, October 2005, p. 8683-8692, Vol. 25, No. 19
0270-7306/05/$08.00+0     doi:10.1128/MCB.25.19.8683-8692.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

pH-Responsive, Posttranslational Regulation of the Trk1 Potassium Transporter by the Type 1-Related Ppz1 Phosphatase

Lynne Yenush,^* Stephanie Merchan, James Holmes, and Ramón Serrano

Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-CSIC, 46022 Valencia, Spain

Received 3 May 2005/ Returned for modification 27 May 2005/ Accepted 5 July 2005

Intracellular pH and K⁺ concentrations must be tightly controlled because they affect many cellular activities, including cell growth and death. The mechanisms of homeostasis of H⁺ and K⁺ are only partially understood. In the yeast Saccharomyces cerevisiae, proton efflux is mediated by the Pma1 H⁺-ATPase. As this pump is electrogenic, the activity of the Trk1 and -2 K⁺ uptake system is crucial for sustained Pma1p operation. The coordinated activities of these two systems determine cell volume, turgor, membrane potential, and pH. Genetic evidence indicates that Trk1p is activated by the Hal4 and -5 kinases and inhibited by the Ppz1 and -2 phosphatases, which, in turn, are inhibited by their regulatory subunit, Hal3p. We show that Trk1p, present in plasma membrane "rafts," physically interacts with Ppz1p, that Trk1p is phosphorylated in vivo, and that its level of phosphorylation increases in ppz1 and -2 mutants. Interestingly, both the interaction with and inhibition of Ppz1p by Hal3p are pH dependent. These results are consistent with a model in which the Ppz1-Hal3 interaction is a sensor of intracellular pH that modulates H⁺ and K⁺ homeostasis through the regulation of Trk1p activity.

---

* Corresponding author. Mailing address: Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-CSIC, Camino de Vera s/n, 46022 Valencia, Spain. Phone: 34 96 387 7860. Fax: 34 96 387 7859. E-mail: lynne{at}ibmcp.upv.es.

Present address: Warwick Horticulture Research International, Wellesbourne, Warwick, CV35 9EF, United Kingdom.

---

Molecular and Cellular Biology, October 2005, p. 8683-8692, Vol. 25, No. 19
0022-538X/05/$08.00+0     doi:10.1128/MCB.25.19.8683-8692.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Martinez-Munoz, G. A., Kane, P. (2008). Vacuolar and Plasma Membrane Proton Pumps Collaborate to Achieve Cytosolic pH Homeostasis in Yeast. J. Biol. Chem. 283: 20309-20319 [Abstract] [Full Text]  
• Fulgenzi, F. R., Peralta, M. L., Mangano, S., Danna, C. H., Vallejo, A. J., Puigdomenech, P., Santa-Maria, G. E. (2008). The Ionic Environment Controls the Contribution of the Barley HvHAK1 Transporter to Potassium Acquisition. Plant Physiol. 147: 252-262 [Abstract] [Full Text]  
• Perez-Valle, J., Jenkins, H., Merchan, S., Montiel, V., Ramos, J., Sharma, S., Serrano, R., Yenush, L. (2007). Key Role for Intracellular K+ and Protein Kinases Sat4/Hal4 and Hal5 in the Plasma Membrane Stabilization of Yeast Nutrient Transporters. Mol. Cell. Biol. 27: 5725-5736 [Abstract] [Full Text]