Contribution of endoplasmic reticulum to Ca2+ signals in Dictyostelium depends on extracellular Ca2+
Contribution of endoplasmic reticulum to Ca2+ signals in Dictyostelium depends on extracellular Ca2+
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DOI：
10.1111/j.1574-6968.2006.00180.x
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发表时间：
2006-04-01
影响因子：
2.1
通讯作者：
Wilczynska, Z
中科院分区：
文献类型：
--
作者：
Fisher, PR;Wilczynska, Z
我们最近报道的第一个分子遗传学证据表明，网骨藻Ca 2+的反应，包括从内质网（ER）的贡献-反应增强的突变体缺乏钙网蛋白或钙连接蛋白，两个主要的Ca 2+结合蛋白在ER，即使流入突变体的Ca 2+减少。与野生型细胞相比，突变体中的ER对应答贡献至少30-70 nM额外的Ca 2+。在这里，我们报告说，这种额外的ER对胞质Ca 2+信号的贡献取决于细胞外Ca 2 +-它不会发生在细胞外Ca 2+的情况下，增加到最大值作为细胞外Ca 2+水平上升到10 μ M，然后保持恒定在细胞外Ca 2+浓度高达至少250 μ M。这些结果表明，Ca 2+内流导致细胞内释放，在最简单的情况下，通过涉及Ca 2+诱导的Ca 2+从ER释放的机制。通过对比，我们表明，机械刺激的Ca 2+反应减少，但仍然发生在细胞外Ca 2+的情况下。与对化学引诱剂的反应不同，机械反应因此包括来自ER的贡献，而不依赖于细胞外Ca 2+。
We recently reported the first molecular genetic evidence that Dictyostelium Ca2+ responses to chemoattractants include a contribution from the endoplasmic reticulum (ER) - responses are enhanced in mutants lacking calreticulin or calnexin, two major Ca2+-binding proteins in the ER, even though the influx of Ca2+ into the mutants is reduced. Compared with wild-type cells, the ER in the mutants contributes at least 30-70 nM additional Ca2+ to the responses. Here we report that this additional ER contribution to the cytosolic Ca2+ signal depends upon extracellular Ca2+- it does not occur in the absence of extracellular Ca2+, increases to a maximum as the extracellular Ca2+ levels rise to 10 mu M and then remains constant at extracellular Ca2+ concentrations up to at least 250 mu M. These results suggest that Ca2+ influx causes the intracellular release, in the simplest scenario by a mechanism involving Ca2+-induced Ca2+ release from the ER. By way of contrast, we show that Ca2+ responses to mechanical stimulation are reduced, but still occur in the absence of extracellular Ca2+. Unlike the responses to chemoattractants, mechanoresponses thus include contributions from the ER that are independent of extracellular Ca2+.