title: Activation of an essential calcium signaling pathway in Saccharomyces cerevisiae by Kch1 and Kch2, putative low-affinity potassium transporters.
abstract: In the budding yeast Saccharomyces cerevisiae, mating pheromones activate a high-affinity Ca(2+) influx system (HACS) that activates calcineurin and is essential for cell survival. Here we identify extracellular K(+) and a homologous pair of transmembrane proteins, Kch1 and Kch2 (Prm6), as necessary components of the HACS activation mechanism. Expression of Kch1 and especially Kch2 was strongly induced during the response to mating pheromones. When forcibly overexpressed, Kch1 and Kch2 localized to the plasma membrane and activated HACS in a fashion that depended on extracellular K(+) but not pheromones. They also promoted growth of trk1 trk2 mutant cells in low K(+) environments, suggesting they promote K(+) uptake. Voltage-clamp recordings of protoplasts revealed diminished inward K(+) currents in kch1 kch2 double-mutant cells relative to the wild type. Conversely, heterologous expression of Kch1 in HEK293T cells caused the appearance of inwardly rectifying K(+) currents. Collectively, these findings suggest that Kch1 and Kch2 directly promote K(+) influx and that HACS may electrochemically respond to K(+) influx in much the same way as the homologous voltage-gated Ca(2+) channels in most animal cell types.
authors.affiliation: Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Stefan
authors.forename: Nannan
authors.initials: N
authors.lastname: Zhang
authors.forename: Takaaki
authors.initials: T
authors.lastname: Sokabe
authors.forename: Alberto
authors.initials: A
authors.lastname: Rivetta
authors.forename: Clifford L
authors.initials: CL
authors.lastname: Slayman
authors.forename: Craig
authors.initials: C
authors.lastname: Montell
authors.forename: Kyle W
authors.initials: KW
authors.lastname: Cunningham
mesh_terms: D015220:Calcium Channels / Q000378:metabolism; D002122:Calcium Chloride / Q000378:metabolism; D020013:Calcium Signaling; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D055786:Gene Knockout Techniques; D057809:HEK293 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000072235:Mating Factor; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000502:physiology; D011188:Potassium / Q000378:metabolism; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C108765:CCH1 protein, S cerevisiae; D015220:Calcium Channels; D027682:Cation Transport Proteins; C582197:Kch1 protein, S cerevisiae; C582198:PRM6 protein, S cerevisiae; D010455:Peptides; D029701:Saccharomyces cerevisiae Proteins; C085258:TRK2 protein, S cerevisiae; C068664:TRK1 protein, S cerevisiae; D000072235:Mating Factor; D002122:Calcium Chloride; D011188:Potassium