Cytoplasmic pH of Dictyostelium discoideum amebae during early development: identification of two cell subpopulations before the aggregation stage.
Cytoplasmic pH of Dictyostelium discoideum amebae during early development: identification of two cell subpopulations before the aggregation stage.
复制标题
DOI：
10.1083/jcb.110.6.1947
复制
发表时间：
1990-06
期刊：
影响因子：
--
通讯作者：
Fechheimer M
中科院分区：
文献类型：
--
作者：
Furukawa R;Wampler JE;Fechheimer M
细胞粘菌盘基网柄菌的发育是通过营养物质的去除而开始的，并导致形成由两种细胞类型（茎细胞和孢子细胞）组成的成熟子实体。大量证据支持这样的假设：细胞质 pH 可能是选择分化前茎或前孢子途径的重要调节因子。我们设计了测量和分析阿米巴盘基网柄菌细胞内 pH 值的方法，以便直接评估细胞质 pH 在调节分化途径中的潜在作用。单个盘状阿米巴变形虫在发育过程中和完整蛞蝓中的细胞内 pH 值已在低光水平显微分光荧光计中使用 pH 敏感指示剂吡喃进行测量。我们使用 ATP 介导的负载方法将吡喃引入这些细胞中。通过 ATP 方法加载的细胞看起来很健康，在发育过程中没有可检测到的缺陷，并且表现出与通过超声处理加载的细胞相似的细胞内 pH 群体分布。发现由单一阿米巴组成的群体的细胞内 pH 在发育过程中经历短暂的酸化，导致细胞内 pH 的双峰分布。通过将两个高斯分布拟合到数据来表征亚群。酸性细胞内pH亚群中的细胞数量在发育开始后4小时达到最大值，并在发育7小时时恢复到较低水平。此外，蛞蝓内单个阿米巴的随机样本的细胞内 pH 值中值为 7.2，几乎与经过类似处理的营养细胞的 pH 值中值 (7.19) 相同。沿蛞蝓前后轴未检测到细胞内 pH 梯度。我们的数据表明，盘基网柄菌在发育聚集阶段之前存在两个不同的细胞亚群，并为细胞内 pH 值的变化有助于盘基网柄菌发育的假设提供了支持。
Development of the cellular slime mold Dictyostelium discoideum is initiated by the removal of nutrients, and results in formation of a mature fruiting body composed of two cell types, the stalk and spore cells. A considerable body of evidence supports the hypothesis that cytoplasmic pH may be an essential regulator of the choice to differentiate in either the prestalk or prespore pathway. We have devised methods for measurement and analysis of intracellular pH in developing Dictyostelium amebae in order to assess directly the potential role of cytoplasmic pH in regulating the pathway of differentiation. The intracellular pH of single D. discoideum amebae during development and in intact slugs has been measured using the pH- sensitive indicator pyranine in a low light level microspectrofluorometer. We have used the ATP-mediated loading method to introduce pyranine into these cells. Cells loaded by the ATP method appear healthy, have no detectable defects in development, and exhibit a similar population distribution of intracellular pH to those loaded by sonication. The intracellular pH of populations comprised of single amebae was found to undergo a transient acidification during development resulting in a bimodal distribution of intracellular pH. The subpopulations were characterized by fitting two gaussian distributions to the data. The number of cells in the acidic intracellular pH subpopulation reached a maximum 4 h after initiation of development, and had returned to a low level by 7 h of development. In addition, a random sample of single amebae within a slug had a median intracellular pH of 7.2, nearly identical to the median pH (7.19) of similarly treated vegetative cells. No gradient of intracellular pH along the anterior to posterior axis of the slug was detected. Our data demonstrate the existence of two distinct subpopulations of cells before the aggregation stage of development in Dictyostelium, and offers support for the hypothesis that changes in intracellular pH contribute to development in D. discoideum.