INTRACELLULAR SIGNALING IN ENDOCRINE CELLS

这个项目解决了内分泌和细胞内的细胞信号级联。 由G蛋白偶联受体操纵的神经内分泌细胞，以及 质膜电事件与细胞周期的相互作用 受体介导的信号传递。目前的重点是职能作用 电压敏感钙通道(VSCC)内钙内流的研究 垂体促性腺激素细胞和下丘脑促性腺激素释放激素神经元。增加了…… 通过这些通道的钙内流与几个不同的 对细胞功能有积极影响。在促性腺激素细胞中，钙内流 通过对InsP3的直接作用调节InsP3诱导的钙振荡 受体和间接地，通过影响补给水平 内质网钙池。InsP3诱导的钙离子偶联 质膜电压尖峰期间的振荡和钙内流 通过钙离子控制钙离子进入来完成。实验 对这一过程的观察和数学模型表明 质膜附近的钙作用于钙激活 质膜上钾离子通道和钙泵的调节 钙离子通过血管内皮细胞进入。除了对阿帕明敏感的钾 通道，电生理研究表明，这些细胞 表达一个额外的钙激活的阿帕明不敏感钾 电流。这一新的通道也参与了感测和 通过重新调制来重新填充ER储存库中的钙含量 自发和激动剂诱发的电活动。电压门控 非激活和激动剂刺激的促性腺激素细胞的钙内流 参与控制促性腺激素的分泌，通过 钙控制胞吐中的Wortmannin敏感步骤。几行 大量证据表明，钙离子内流控制的分泌 通过钙调蛋白-肌球蛋白轻链激酶依赖的机制， 在微摩尔浓度范围内受Wortmannin的影响。行动 电位驱动的钙内流也控制神经肽的分泌 永生化的促性腺激素释放激素神经元。在这些细胞中，电压门控钙离子进入 和蛋白激酶C以独立但协同的方式作用于 调节磷脂酶D的活性，这有助于分泌 促性腺激素释放激素神经元的反应。因此，促性腺激素释放激素分泌的电活动 神经元参与神经细胞间的功能偶联 钙动员受体和磷脂酶D途径。这些 观察为理解相互作用提供了基础 质膜和内质网钙通道 作为酶活性和胞吐作用。此外，他们强调 钙离子在激动剂诱导中正反馈作用的复杂性 信号和激素分泌。

This project addresses the cellular signaling cascade in endocrine and neuroendocrine cells operated by G protein-coupled receptors, and the interactions between plasma membrane electrical events and receptor-mediated signaling. Current emphasis is on the functional role of calcium influx through voltage-sensitive calcium channels (VSCC) in pituitary gonadotrophs and hypothalamic GnRH neurons. An increase in calcium influx through these channels is associated with several distinct positive effects on cellular functions. In gonadotrophs, calcium influx modulates InsP3-induced calcium oscillations via a direct effect on InsP3 receptors and indirectly, by affecting the level of repletion of the endoplasmic reticulum calcium pool. The coupling of InsP3-induced calcium oscillations and calcium influx during plasma membrane voltage spikes is accomplished through calcium-controlled calcium entry. Experimental observations and a mathematical model of this process indicate that calcium in the vicinity of the plasma membrane acts on calcium-activated potassium channels and calcium pumps in the plasma membrane to regulate calcium entry through VSCC. In addition to apamin-sensitive potassium channels, electrophysiological investigations indicate that these cells express an additional calcium-activated apamin-insensitive potassium current. This novel channel also participates in the sensing and refilling of calcium content in the ER stores by remodulation of spontaneous and agonist-induced electrical activity. Voltage-gated calcium entry in non-activated and agonist-stimulated gonadotrophs participates in the control of gonadotropin secretion through a wortmannin-sensitive step in calcium-controlled exocytosis. Several lines of evidence suggest that calcium influx-controlled secretion occurs through a calmodulin-myosin light chain kinase-dependent mechanism, which is affected by wortmannin in a micromolar concentration-range. Action potential-driven calcium influx also controls neuropeptide secretion from immortalized GnRH neurons. In these cells, voltage-gated calcium entry and protein kinase C act in an independent but cooperative manner to regulate phospholipase D activity, which contributes to the secretory response in GnRH neurons. Thus, the electrical activity of GnRH-secreting neurons participates in the functional coupling between calcium-mobilizing receptors and the phospholipase D pathway. These observations provide the basis for understanding the interactions between the plasma membrane and endoplasmic reticulum calcium channels, as well as enzymatic activity and exocytosis. Moreover, they emphasize the complexity in the positive feedback role of calcium in agonist-induced signaling and hormone secretion.