Protein phosphatase type 1 and yeast casein kinase 1 cooperatively
regulate ion homeostasis.
Tara Williams-Hart (1), Kelly Tatchell (2)
(1) 1501 Kings Highway, Shreveport, LA 71130;
(2) Biochemistry, LSU Health Sciences Center, 1501 Kings Highway,
Shreveport, LA 71130, United States of America
Several alleles of GLC7, encoding type 1 protein phosphatase
(PP1), confer sensitivity to a wide range of cations and drugs. This
phenotype is characteristic of genes involved in regulating ion
transport. To identify potential downstream targets of Glc7p-specific
regulation of ion transport, we isolated dosage suppressors of the
cation and drug sensitivities of these mutants. The sodium and lithium
sensitivities of the glc7-109 (K259A R260A) mutant are suppressed
by overexpression of YCK2. YCK2 and YCK1 are an
essential gene pair that encode the membrane-associated forms of yeast
casein kinase 1, which was previously shown to influence cell morphology
and ion homeostasis. In our strain background, a yck1::LEU2 yck2-2ts (yckts) mutant is sensitive to
multiple cations and the drug, paromomycin sulfate. The
yckts glc7-109 mutant is more sensitive to cations and
drugs than the single mutants. Furthermore, the glc7-109 mutation
enhances the temperature sensitivity of the yckts
mutant without affecting its morphological defect, suggesting that Glc7p
and Yck2p regulate a common pathway. A second high-copy suppressor
plasmid containing YIL121W, a member of the major facilitator
superfamily with homology to a putative H+:drug antiporter,
suppresses the sodium, lithium and manganese defects of the glc7-109 mutant. Together these results suggest that Glc7p, yeast casein
kinase 1 and a putative H+:drug antiporter may cooperatively
regulate ion homeostasis.
Return to YGM 2002 Home at SGD