INTRACELLULAR SIGNALING IN ENDOCRINE CELLS

该项目致力于内分泌和免疫系统中的细胞信号级联， 由G蛋白偶联受体操纵的神经内分泌细胞， 质膜电事件之间的相互作用 受体介导的信号传导。目前的重点是职能作用 通过电压敏感性钙通道（VSCC）的钙内流 垂体促性腺激素细胞和下丘脑GnRH神经元。增加 通过这些通道的钙内流与几种不同的 对细胞功能的积极影响。在促性腺激素细胞中， 通过对InsP 3的直接作用调节InsP 3诱导的钙振荡 受体和间接，通过影响的饱足水平， 内质网钙池。InsP 3诱导的钙离子偶联 在质膜电压尖峰期间的振荡和钙内流， 通过钙控制的钙进入来完成。实验 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的 钾通道和钙泵在质膜调节 钙通过VSCC进入。除了对apamin敏感的钾 通道，电生理研究表明，这些细胞， 表达额外的钙激活的apamin不敏感钾 电流这种新颖的通道也参与了感测和 通过重新调节钙离子， 自发和激动剂诱导的电活动。电压依赖 非激活和激动剂刺激的促性腺激素细胞中的钙内流 参与控制促性腺激素的分泌， 钙控制胞吐中渥曼凝敏感步骤。几行 的证据表明，钙流入控制的分泌发生 通过钙调蛋白-肌球蛋白轻链激酶依赖性机制， 在微摩尔浓度范围内受渥曼青霉素的影响。行动 电位驱动的钙内流也控制神经肽的分泌， 永生化GnRH神经元。在这些细胞中，电压门控钙离子进入 和蛋白激酶C以独立但合作的方式起作用， 调节磷脂酶D的活性，这有助于分泌 GnRH神经元的反应。因此，GnRH分泌的电活动 神经元参与神经元之间的功能耦合， 钙动员受体和磷脂酶D途径。这些 观察为理解这些相互作用提供了基础。 质膜和内质网钙通道，以及 如酶活性和胞吐作用。此外，他们强调， 激动剂诱导的钙离子正反馈作用的复杂性 信号传导和激素分泌。

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.