The Ca2+ Homeostasis defects in a pgm2Δ strain of Saccharomyces cerevisiae are caused by excessive vacuolar Ca2+ uptake mediated by the Ca2+-ATPase Pmc1p
The Ca2+ Homeostasis defects in a pgm2Δ strain of Saccharomyces cerevisiae are caused by excessive vacuolar Ca2+ uptake mediated by the Ca2+-ATPase Pmc1p
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DOI：
10.1074/jbc.m400833200
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发表时间：
2004-09-10
影响因子：
4.8
通讯作者：
Bedwell, DM
中科院分区：
文献类型：
--
作者：
Aiello, DP;Fu, LW;Bedwell, DM
当酵母细胞以半乳糖为碳源和能源生长时，失去主要的磷酸葡萄糖变位酶(PGM)会导致葡萄糖1-磷酸的积累。值得注意的是，pgm2Delta菌株在这些条件下生长时，也表现出严重的细胞内钙稳态失衡。在目前的研究中，我们更详细地研究了pgm2Delta突变如何改变酵母的钙稳态。我们发现，从葡萄糖转变为半乳糖作为碳源，野生型细胞的细胞钙摄取率增加了2倍，而pgm2 Delta突变体的细胞钙摄取率增加了8倍。Pmc1基因编码空泡钙-ATPase Pmc1p，它的中断抑制了在pgm2Delta菌株中观察到的与钙相关的表型。这表明过度的液泡钙摄取与钙稳态的这些缺陷密切相关。一项旨在测量细胞内钙离子隔离的体外实验证实，pgm2Delta突变株含有比野生型菌株更高水平的Pmc1p依赖的钙转运活性。我们发现，这种空泡钙摄取速度的增加也与pgm2Delta突变体的未折叠蛋白反应的大量诱导相一致，这表明内质网室的钙摄取减少。这些结果表明，先前被证明与pgm2Delta突变相关的过度的钙摄取和积累是由于细胞内钙离子在不同细胞内的分布严重不平衡所致。
Loss of the major isoform of phosphoglucomutase (PGM) causes an accumulation of glucose 1-phosphate when yeast cells are grown with galactose as the carbon and energy source. Remarkably, the pgm2Delta strain also exhibits a severe imbalance in intracellular Ca2+ homeostasis when grown under these conditions. In the present study, we examined how the pgm2Delta mutation alters yeast Ca2+ homeostasis in greater detail. We found that a shift from glucose to galactose as the carbon source resulted in a 2-fold increase in the rate of cellular Ca2+ uptake in wild-type cells, whereas Ca2+ uptake increased 8-fold in the pgm2Delta mutant. Disruption of the PMC1 gene, which encodes the vacuolar Ca2+-ATPase Pmc1p, suppressed the Ca2+-related phenotypes observed in the pgm2Delta strain. This suggests that excessive vacuolar Ca2+ uptake is tightly coupled to these defects in Ca2+ homeostasis. An in vitro assay designed to measure Ca2+ sequestration into intracellular compartments confirmed that the pgm2Delta mutant contained a higher level of Pmc1p-dependent Ca2+ transport activity than the wild-type strain. We found that this increased rate of vacuolar Ca2+ uptake also coincided with a large induction of the unfolded protein response in the pgm2Delta mutant, suggesting that Ca2+ uptake into the endoplasmic reticulum compartment was reduced. These results indicate that the excessive Ca2+ uptake and accumulation previously shown to be associated with the pgm2Delta mutation are due to a severe imbalance in the distribution of cellular Ca2+ into different intracellular compartments.