A homolog of voltage-gated Ca2+ channels stimulated by depletion of secretory Ca2+ in yeast
A homolog of voltage-gated Ca2+ channels stimulated by depletion of secretory Ca2+ in yeast
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DOI：
10.1128/mcb.20.18.6686-6694.2000
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发表时间：
2000-09-01
影响因子：
5.3
通讯作者：
Cunningham, KW
中科院分区：
文献类型：
--
作者：
Locke, EG;Bonilla, M;Cunningham, KW
在动物细胞中，容量性钙离子进入（CCE）机制专门响应秘书细胞器中钙离子（Ca 2+）的耗尽而被激活。CCE用于补充这些细胞器，并增强对细胞质中升高的游离Ca2+浓度作出响应的信号传导途径。CCE调节的机制尚不清楚，因为其基本成分很少被确定。我们在这里首次表明，芽殖酵母酿酒酵母采用CCE样机制，以补充Ca2+商店内的秘书途径，突变体缺乏Pmr1p，一个保守的Ca2+泵的秘书途径，表现出较高的Ca2+流入率相对于野生型细胞由于高亲和力的Ca2+摄取系统的刺激。通过表达哺乳动物SERCA泵，在pmr1突变体中阻断了该钙摄取系统的刺激。高亲和力的Ca2+摄取系统也刺激野生型细胞过表达空泡Ca2+转运蛋白，与Pmr1p竞争底物。酵母突变体的筛选，特别是在高亲和力的Ca2+摄取系统缺陷揭示了两个基因，CCH1和MID1，以前牵连在Ca2+流入交配信息素。Cch1p和Mid1p定位于质膜，从溶解的膜共免疫沉淀，并显示在一个单一的途径，确保足够水平的Ca2+提供给Pmr1p，以维持分泌和生长的功能在一起。Cch1p和Mid1p的表达在pmr1突变体中不受影响。这些证据支持酵母在哺乳动物细胞中维持与CCE相关的稳态机制的假设。Cch1p和电压门控Ca2+通道的催化亚基之间的同源性提出了这样的可能性，即在相同的情况下，动物细胞中的CCE可能涉及Cch1p的同源物和保守的调节机制。
In animal cells, capacitative calcium entry (CCE) mechanisms become activated specifically in response to depletion of calcium ions (Ca2+) from secretary organelles. CCE serves to replenish those organelles and to enhance signaling pathways that respond to elevated free Ca2+ concentrations in the cytoplasm. The mechanism of CCE regulation is not understood because few of its essential components have been identified. We show here for the first time that the budding yeast Saccharomyces cerevisiae employs a CCE-like mechanism to refill Ca2+ stores within the secretary pathway, Mutants lacking Pmr1p, a conserved Ca2+ pump in the secretary pathway, exhibit higher rates of Ca2+ influx relative to wild-type cells due to the stimulation of a high-affinity Ca2+ uptake system. Stimulation of this Ca2+ uptake system nas blocked in pmr1 mutants by expression of mammalian SERCA pumps. The high-affinity Ca2+ uptake system was also stimulated in wild-type cells overexpressing vacuolar Ca2+ transporters that competed with Pmr1p for substrate. A screen for yeast mutants specifically defective in the high-affinity Ca2+ uptake system revealed two genes, CCH1 and MID1, previously implicated in Ca2+ influx in response to mating pheromones. Cch1p and Mid1p were localized to the plasma membrane, coimmunoprecipitated from solubilized membranes, and shown to function together within a single pathway that ensures that adequate levels of Ca2+ are supplied to Pmr1p to sustain secretion and growth. Expression of Cch1p and Mid1p was not affected in pmr1 mutants. The evidence supports the hypothesis that yeast maintains a homeostatic mechanism related to CCE in mammalian cells. The homology between Cch1p and the catalytic subunit of voltage-gated Ca2+ channels raises the possibility that in same circumstances CCE in animal cells may involve homologs of Cch1p and a conserved regulatory mechanism.