An activity-dependent increased role for L-type calcium channels in exocytosis is regulated by adrenergic signaling in chromaffin cells.
An activity-dependent increased role for L-type calcium channels in exocytosis is regulated by adrenergic signaling in chromaffin cells.
复制标题
L 型钙通道在胞吐作用中的活性依赖性增强作用受到嗜铬细胞中肾上腺素能信号的调节。
DOI：
10.1016/j.neuroscience.2006.08.001
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发表时间：
2006
期刊：
影响因子：
3.3
通讯作者：
Smith,C
中科院分区：
文献类型：
--
作者：
Polo-Parada,L;Chan,S-A;Smith,C
肾上腺髓质的嗜铬细胞代表交感神经系统的主要输出。它们的电刺激引起大而致密的核心颗粒与细胞膜的融合以及多个递质分子的胞吐释放到循环中。在那里，递质有助于调节生物体的基本代谢。在生理活动下，颗粒融合和递质释放受到活动依赖性 Ca2+ 流入的限制，通过电压门控钙通道的多种亚型进入。在这项研究中，我们利用穿孔贴片电压钳记录，并用类似动作电位的波形对小鼠嗜铬细胞进行原位去极化，以模拟生理放电。我们通过特定亚型测量钙流入，并测量细胞电容作为颗粒融合的指标。结合这些方法，我们计算了不同生理活动水平下 L 型、N 型、P/Q 型和 R 型钙通道的特定刺激分泌效率。通过所有通道亚型的电流流入表现出活动依赖性抑制。正如预期的那样，P/Q 型通道虽然负责适度的 Ca2+ 内流，但在所有条件下都与儿茶酚胺分泌紧密相关。我们进一步发现，在急性应激反应下，为匹配交感神经输入而设计的刺激会招募 L 型通道，使其达到刺激分泌效率增强的状态。 N 型和 R 型通道不进行活性依赖性募集，并与分泌保持松散耦合。因此，只有L型通道在生理刺激下其刺激分泌功能表现出活动依赖性变化。最后，我们发现用 β-肾上腺素能激动剂异丙肾上腺素治疗可以特异性阻断 L 型通道刺激分泌功能的增加。因此，细胞放电的增加特异性地增强了嗜铬细胞中 L 型 Ca2+ 通道的刺激-分泌耦合。该机制受肾上腺素信号通路调节。
Chromaffin cells of the adrenal medulla represent a primary output of the sympathetic nervous system. Their electrical stimulation evokes the fusion of large dense core granules with the cell membrane and the exocytic release of multiple transmitter molecules into the circulation. There the transmitters contribute to the regulation of basic metabolism of the organism. Under physiological activity, granule fusion and transmitter release are limited by activity-dependent Ca2+influx, entering through multiple isoforms of voltage-gated calcium channels. In this study we utilize perforated-patch voltage-clamp recordings and depolarize mouse chromaffin cells in situ with action potential-like waveforms to mimic physiological firing. We measure calcium influx through specific isoforms and measure cell capacitance as an index of granule fusion. Combining these approaches we calculate specific stimulus-secretion efficiencies for L-type, N-type, P/Q-type and R-type calcium channels under varied physiological activity levels. Current influx through all channel subtypes exhibited an activity-dependent depression. As expected P/Q-type channels, while responsible for modest Ca2+influx, are tightly coupled to catecholamine secretion under all conditions. We further find that stimulation designed to match sympathetic input under the acute stress response recruits L-type channels to a state of enhanced stimulus-secretion efficiency. N- and R-type channels do not undergo activity-dependent recruitment and remain loosely coupled to the secretion. Thus, only L-type channels exhibit activity-dependent changes in their stimulus-secretion function under physiological stimulation. Lastly, we show that treatment with the β-adrenergic agonist, isoproterenol, specifically blocks the increase in the stimulus-secretion function of L-type channels. Thus, increased cell firing specifically enhances stimulus-secretion coupling of L-type Ca2+channels in chromaffin cells in situ. This mechanism is regulated by an adrenergic signaling pathway.