The protein phosphatase calcineurin is essential for NaCl tolerance of Saccharomyces cerevisiae.
NaCl-sensitive yeast mutants were isolated to identify genes essential for NaCl tolerance. Complementation of a mutant highly sensitive to Na+ and Li+ led to the isolation of the CNB1 gene. This gene encodes the regulatory subunit (CNB) of the Ca2+/calmodulin-dependent protein phosphatase calcineurin. Cells deficient in CNB accumulated Li+ due to reduced expression of ENA1, a gene encoding a P-type ATPase involved in Na+ and Li+ efflux. In addition, the K+ transport system of cnb1 delta cells was not converted to the high affinity state that facilitates better discrimination of K+ over Na+. Thus the cnb1 delta strain resembled a trk1 mutant. These results indicate that adaptation to NaCl stress in Saccharomyces cerevisiae requires a signal transduction pathway involving Ca2+ and protein phosphorylation-dephosphorylation. In this pathway, calcineurin would coordinate gene expression and activity of ion transporters to facilitate ion homeostasis.
Mendoza
I
I
Instituto de Recursos Naturales y Agrobiologia, Consejo Superior de Investigaciones Cientificas, Sevilla, Spain.
Rubio
F
F
Rodriguez-Navarro
A
A
Pardo
J M
JM
D000251:Adenosine Triphosphatases / Q000235:genetics; D001483:Base Sequence; D001693:Biological Transport, Active; D019703:Calcineurin; D002148:Calmodulin-Binding Proteins / Q000502:physiology*; D027682:Cation Transport Proteins; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000235:genetics; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D006706:Homeostasis; D018021:Lithium Chloride; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000502:physiology*; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase; D014882:Water-Electrolyte Balance
D002148:Calmodulin-Binding Proteins; D027682:Cation Transport Proteins; C086375:ENA1 protein, S cerevisiae; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D012965:Sodium Chloride; D012964:Sodium; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D000251:Adenosine Triphosphatases; D000254:Sodium-Potassium-Exchanging ATPase; D018021:Lithium Chloride