Contributions of intracellular compartments to calcium dynamics: Implicating an acidic store
Contributions of intracellular compartments to calcium dynamics: Implicating an acidic store
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DOI：
10.1111/j.1600-0854.2006.00432.x
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发表时间：
2006-07-01
期刊：
影响因子：
4.5
通讯作者：
Hille, B
中科院分区：
文献类型：
--
作者：
Duman, JG;Chen, LY;Hille, B
许多细胞在长时间去极化后显示出升高的胞质Ca 2+的平台，这表明细胞内隔室如线粒体和内质网（ER）的Ca 2+释放延迟。小鼠胰腺β-细胞在30 s去极化后显示Ca 2+的毒胡萝卜素敏感性平台（“驼峰”），但在10 s去极化后不显示。令人惊讶的是，这个驼峰主要依赖于线粒体或ER以外的隔室。在阻断线粒体Na+-Ca 2+交换后，它仅减少22%，在一起阻断ryanodine或IP 3受体后仅减少18%。此外，ER Ca 2+的时间过程中测量的目标cameleon不依赖于去极化的持续时间。相反，用二肽甘氨酰苯丙氨酸β-萘酰胺（一种常用于裂解溶酶体的工具）处理，驼峰减少了35%。我们表明，这种二肽不干扰ER功能，但它裂解酸性车厢和释放Ca 2+到胞质溶胶。此外，它诱导胰岛素颗粒渗漏并可能溶解胰岛素颗粒，并停止分泌颗粒向β细胞中易于释放的池的动员。我们的结论是，二肽妥协致密的核心分泌颗粒，这些颗粒包括一个酸性的钙储存在β-细胞的加载和/或释放是敏感的毒胡萝卜素和释放后，胞浆Ca 2+升高Ca 2+。
Many cells show a plateau of elevated cytosolic Ca2+ after a long depolarization, suggesting delayed Ca2+ release from intracellular compartments such as mitochondria and endoplasmic reticulum (ER). Mouse pancreatic beta-cells show a thapsigargin-sensitive plateau ('hump') of Ca2+ after a 30 s depolarization but not after a 10 s depolarization. Surprisingly, this hump depends primarily on compartments other than the mitochondria or ER. It is reduced by only 22% upon blocking mitochondrial Na+-Ca2+ exchange and by only 18% upon blocking ryanodine or IP3 receptors together. Further, the time course of ER Ca2+ measured by a targeted cameleon does not depend on the duration of depolarizations. Instead, the hump is reduced 35% by treatments with the dipeptide glycylphenylalanine beta-napthylamide, a tool often used to lyse lysosomes. We show that this dipeptide does not disturb ER functions, but it lyses acidic compartments and releases Ca2+ into the cytosol. Moreover, it induces leaks in and possibly lyses insulin granules and stops mobilization of secretory granules to the readily releasable pool in beta-cells. We conclude that the dipeptide compromises dense-core secretory granules and that these granules comprise an acidic calcium store in beta-cells whose loading and/or release is sensitive to thapsigargin and which releases Ca2+ after cytosolic Ca2+ elevation.