Calcineurin inhibits VCX1-dependent H+/Ca2+ exchange and induces Ca2+ ATPases in Saccharomyces cerevisiae.
The PMC1 gene in Saccharomyces cerevisiae encodes a vacuolar Ca2+ ATPase required for growth in high-Ca2+ conditions. Previous work showed that Ca2+ tolerance can be restored to pmc1 mutants by inactivation of calcineurin, a Ca2+/calmodulin-dependent protein phosphatase sensitive to the immunosuppressive drug FK506. We now report that calcineurin decreases Ca2+ tolerance of pmc1 mutants by inhibiting the function of VCX1, which encodes a vacuolar H+/Ca2+ exchanger related to vertebrate Na+/Ca2+ exchangers. The contribution of VCX1 in Ca2+ tolerance is low in strains with a functional calcineurin and is high in strains which lack calcineurin activity. In contrast, the contribution of PMC1 to Ca2+ tolerance is augmented by calcineurin activation. Consistent with these positive and negative roles of calcineurin, expression of a vcx1::lacZ reporter was slightly diminished and a pmc1::lacZ reporter was induced up to 500-fold by processes dependent on calcineurin, calmodulin, and Ca2+. It is likely that calcineurin inhibits VCX1 function mainly by posttranslational mechanisms. Activities of VCX1 and PMC1 help to control cytosolic free Ca2+ concentrations because their function can decrease pmc1::lacZ induction by calcineurin. Additional studies with reporter genes and mutants indicate that PMR1 and PMR2A, encoding P-type ion pumps required for Mn2+ and Na+ tolerance, may also be induced physiologically in response to high-Mn2+ and -Na+ conditions through calcineurin-dependent mechanisms. In these situations, inhibition of VCX1 function may be important for the production of Ca2+ signals. We propose that elevated cytosolic free Ca2+ concentrations, calmodulin, and calcineurin regulate at least four ion transporters in S. cerevisiae in response to several environmental conditions.
Cunningham
K W
KW
Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Fink
G R
GR
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism*; D002122:Calcium Chloride / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000096:biosynthesis* / Q000378:metabolism*; D003001:Cloning, Molecular; D004285:Dogs; D004790:Enzyme Induction; D005800:Genes, Fungal; D005838:Genotype; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D053499:Plasma Membrane Calcium-Transporting ATPases; D010957:Plasmids; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014617:Vacuoles / Q000201:enzymology
C085484:PMC1 protein, S cerevisiae; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D053499:Plasma Membrane Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002122:Calcium Chloride; D002118:Calcium