ATP regulates anion channel-mediated organic osmolyte release from cultured rat astrocytes via multiple Ca2+-sensitive mechanisms.
ATP regulates anion channel-mediated organic osmolyte release from cultured rat astrocytes via multiple Ca2+-sensitive mechanisms.
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ATP 通过多种 Ca2 敏感机制调节培养的大鼠星形胶质细胞中阴离子通道介导的有机渗透剂的释放。
DOI：
10.1152/ajpcell.00330.2004
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
Kimelberg,HaroldK
中科院分区：
文献类型：
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作者：
Mongin,AlexanderA;Kimelberg,HaroldK
无处不在表达的体积调节阴离子通道（vrac）在细胞肿胀时被激活，但在非肿胀细胞中也可能表现出有限的活性。vrac可以渗透到无机阴离子和小的有机渗透物，包括氨基酸天冬氨酸、谷氨酸和牛磺酸。最近的一些报道表明，神经递质或激素，如ATP和抗利尿激素，诱导或强烈增强星形胶质细胞全细胞Cl -电流和氨基酸释放，而这些被VRAC阻滞剂抑制。在本研究中，我们探索了在大鼠原代星形胶质细胞培养中，通过假定的VRAC途径介导ATP和-[3H]天冬氨酸释放的细胞内信号机制。细胞暴露在中等（5%）或大量（30%）的介质渗透压降低中。在中度肿胀和重度肿胀的细胞中，ATP强烈地增强了-[3H]天冬氨酸的释放。这些ATP效应被BAPTA-AM、钙调素抑制剂或蛋白激酶C （PKC）和钙调素依赖性激酶II （CaMK II）抑制剂的细胞内Ca2+螯合阻断（抑制率≥80%）。相比之下，由大量低渗肿胀激活的对照[3H]天冬氨酸释放对相同药物的敏感性很小（抑制≤25%）。这些数据表明，ATP通过两个独立的Ca2+敏感信号级联调节VRAC活性，包括PKC和CaMK II，细胞肿胀本身通过一个独立的Ca2+/钙调素独立的信号机制激活VRAC。钙离子依赖的有机渗透物通过vrac释放可能有助于大脑中这些通道的生理功能，包括星形胶质细胞到神经元的细胞间通讯。
Ubiquitously expressed volume-regulated anion channels (VRACs) are activated in response to cell swelling but may also show limited activity in nonswollen cells. VRACs are permeable to inorganic anions and small organic osmolytes, including the amino acids aspartate, glutamate, and taurine. Several recent reports have demonstrated that neurotransmitters or hormones, such as ATP and vasopressin, induce or strongly potentiate astrocytic whole cell Cl−currents and amino acid release, which are inhibited by VRAC blockers. In the present study, we explored the intracellular signaling mechanisms mediating the effects of ATP ond-[3H]aspartate release via the putative VRAC pathway in rat primary astrocyte cultures. Cells were exposed to moderate (5%) or substantial (30%) reductions in medium osmolarity. ATP strongly potentiatedd-[3H]aspartate release in both moderately swollen and substantially swollen cells. These ATP effects were blocked (≥80% inhibition) by intracellular Ca2+chelation with BAPTA-AM, calmodulin inhibitors, or a combination of the inhibitors of protein kinase C (PKC) and calmodulin-dependent kinase II (CaMK II). In contrast, controld-[3H]aspartate release activated by the substantial hyposmotic swelling showed little (≤25% inhibition) sensitivity to the same pharmacological agents. These data indicate that ATP regulates VRAC activity via two separate Ca2+-sensitive signaling cascades involving PKC and CaMK II and that cell swelling per se activates VRACs via a separate Ca2+/calmodulin-independent signaling mechanism. Ca2+-dependent organic osmolyte release via VRACs may contribute to the physiological functions of these channels in the brain, including astrocyte-to-neuron intercellular communication.