PROPERTIES OF K+ CURRENT THAT CONTROLS SECRETION

控制分泌的 K 电流的特性

• 批准号: 2749510
• 负责人: JOHN J ENYEART
• 金额: $ 14.57万
• 依托单位: OHIO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-09-13 至 1999-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2749510
• 关键词: G protein; Xenopus; Xenopus oocyte; adrenocorticotropic hormone; angiotensin II; biological signal transduction; calcium flux; corticosteroids; cyclic nucleoside monophosphate; hormone regulation /control mechanism; molecular cloning; nucleic acid sequence; phosphorylation; potassium channel; tissue /cell culture; transfection; voltage /patch clamp

In mammals, corticosteroid secretion by cells of the adrenal gland is controlled by peptide hormones including adrenocorticotropic hormone (ACTH) and angiotensin II (AII). Glucocorticoids such as cortisol act on cells of the liver, muscle and adipose tissue to enhance glucose synthesis-and to promote the breakdown of fat and proteins. Aberrant corticosteroid secretion is responsible for serious pathology including Cushing's and Addison's diseases. The mineralocorticoid aldosterone acts to maintain fluid and electrolyte balance. Inappropriate aldolsterone secretion is manifested as hypo- or hypertension. The cellular mechanisms by which peptide hormones regulate corticosteroid secretion are not understood. In many secretory cells, hormone production is coupled to membrane depolarization through activation of voltage-gated Ca2+ channels. Bovine adrenocortical cells possess a novel K+ channel (IAC) that sets the membrane potential of these cells. Importantly, both ACTH and AII inhibit IAC and depolarize adrenal cells at equivalent subnanomolar concentrations. The convergent inhibition of IAC by these two peptides suggests a physiological mechanism whereby biochemical signals at the cell membrane can be coupled to depolarization-dependent Ca2+ entry and steroid hormone secretion. Because IAC appears to act pivotally in transducing biochemical signals to electrical events involved in secretion, a detailed characterization of this current, the underlying channels and the signalling pathways that regulate IAC activity will be essential to understanding adrenal cortical physiology. In the proposed studies, IAC in bovine and human adrenal zona fasciculata cells will be examined with patch voltage clamp techniques. Functional expression of IAC in Xenopus oocytes will be used to clone IAC channel cDNA. The aims of the proposed research will be: 1) To characterize IAC with respect to biophysical properties, pharmacology, and modulation by metabolic factors and enzymes; 2) To identify and characterize the signalling pathways and molecular mechanisms by which ACTH inhibits IAC; 3) To determine whether IAC is present and regulated by AII and ACTH in human adrenocortical cells; 4) To clone and sequence the cDNA for IAC by expression cloning in Xenopus oocytes.

在哺乳动物中，肾上腺细胞分泌的皮质类固醇是 受肽激素（包括促肾上腺皮质激素）控制 (ACTH) 和血管紧张素 II (AII)。糖皮质激素如皮质醇作用于 肝脏、肌肉和脂肪组织细胞提高血糖 合成——并促进脂肪和蛋白质的分解。异常 皮质类固醇分泌导致严重病理，包括 库欣病和艾迪生病。盐皮质激素醛固酮的作用 以维持液体和电解质平衡。醛固酮不适当 分泌不足则表现为低血压或高血压。 肽激素调节皮质类固醇的细胞机制 分泌不了解。在许多分泌细胞中，激素的产生 通过电压门控的激活与膜去极化耦合 Ca2+ 通道。牛肾上腺皮质细胞具有新型 K+ 通道 （IAC）设定这些细胞的膜电位。重要的是，两者 ACTH 和 AII 抑制 IAC 并在同等条件下使肾上腺细胞去极化 亚纳摩尔浓度。这些对 IAC 的收敛抑制 两种肽表明了一种生理机制，其中生化 细胞膜上的信号可以耦合到去极化依赖性 Ca2+ 进入和类固醇激素分泌。 因为 IAC 似乎在生化信号转导中发挥着关键作用 对于分泌中涉及的电事件，详细的表征 该电流的基础通道和信号传导途径 调节 IAC 活动对于了解肾上腺皮质至关重要 生理。 在拟议的研究中，牛和人肾上腺束状带中的 IAC 将使用贴片电压钳技术检查细胞。功能性 IAC 在非洲爪蟾卵母细胞中的表达将用于克隆 IAC 通道 cDNA。拟议研究的目标是： 1) 为了表征 IAC 的生物物理特性， 药理学以及代谢因子和酶的调节； 2) 识别和表征信号通路和分子 ACTH 抑制 IAC 的机制； 3) 确定IAC是否存在并受AII和ACTH的调节 人肾上腺皮质细胞； 4) 克隆并测序 IAC 的 cDNA 非洲爪蟾卵母细胞中的表达克隆。