The yeast secretory pathway is perturbed by mutations in PMR1, a member of a Ca2+ ATPase family

Elevated cytosolic free Ca2+ concentrations and massive Ca2+ accumulation within vacuoles, in yeast mutant lacking PMR1, a homolog of Ca2+‐ATPase

“…The growth rate of the pmrl mutant cells was slightly stimulated by the addition of 20 mM Ca ~+ to the medium, markedly inhibited by reducing external Ca 2+ by EGTA, as previously reported [1,4], but was reduced by only 12% (which is no more than the decrease in the growth rate of the WT cells) by increasing strains. Cells of the indicated strains were grown in YPD medium labeled with 4~Cae+ to the stationary phase.…”

“…It was suggested that PMR1 encodes a Ca2+-ATPase. This suggestion was based on sequence homology to mammalian Ca2+-ATPase, inhibition of the growth of the prnrl mutant in very low Ca 2+ medium, and reversal of the defects in Golgi function in the pmrl mutant by the addition of extracellular Ca 2+ [1,4]. In the present study we showed that deletion of PMR1 but not of PMR2 causes elevation of [Ca2+]i.…”

“…Cls2p/ Csg2p appears to regulate Ca 2+ sequestration into the ER, since cls2 null mutant cells do not grow in high Ca 2+ media and when grown in low Ca 2+ medium sequester huge amounts of Ca 2+ into a non-vacuolar Ca 2+ pool, probably the ER [20,21]. The third Ca 2+ transporter is Pmrlp [1] which was localized in Golgi-like particles by immunofluorescence staining of yeast cells expressing epitope tagged PMR1 [4]. It was shown in the present study that Pmrlp participates in lowering [Ca2+]i in cells exposed to moderately high [Ca~+]out, probably by pumping Ca 2+ into the Golgi.…”

“…Two genes for P-type ATPase, PMR1 and PMR2, were cloned by Rudolph et al [1] PMR2 was found later to encode a plasma membrane Na+-ATPase responsible for resistance to high concentrations of Na ÷ and Li + [12][13][14]. It was suggested that PMR1 encodes a Ca2+-ATPase.…”

“…]?he cells of the pmrl mutant and the WT strain were harvested from the growth medium, washed 4 times with distilled water and resuspended (2x 108 cells/ml) in buffer-glucose solution containing MES/DMG buffer (25 mM, pH 5.0) and glucose (20 mM [1,4], the isogenic pmr2 mutant cells, lacking a cell-membrane Na+-ATPase [12][13][14] and the isogenic WT cells grew well in YPD medium containing 0.3 mM Ca 2+. The growth rate of the pmrl mutant cells was slightly stimulated by the addition of 20 mM Ca ~+ to the medium, markedly inhibited by reducing external Ca 2+ by EGTA, as previously reported [1,4], but was reduced by only 12% (which is no more than the decrease in the growth rate of the WT cells) by increasing strains.…”