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; 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，肾上腺细胞的皮质类固醇分泌是 由包括肾上腺皮质激素在内的肽激素控制 （ACTH）和血管紧张素II（AII）。糖皮质激素（例如皮质醇）作用于 肝脏，肌肉和脂肪组织的细胞以增强葡萄糖 合成并促进脂肪和蛋白质的分解。异常 皮质类固醇分泌负责严重的病理学 Cushing和Addison的疾病。矿物皮质激素醛固酮作用 维持流体和电解质平衡。不适当的藻酮 分泌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，激素产生 通过激活电压门控与膜去极化耦合 CA2+通道。牛肾上腺皮质细胞具有新颖的K+通道 （IAC）设定了这些细胞的膜电位。重要的是，两者俩 ACTH和AII抑制IAC并在等效上去极化肾上腺细胞 亚奈摩尔浓度。这些对IAC的收敛抑制 两种肽提出了一种生理机制 细胞膜处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似乎在转导的生化信号中起着关键作用 分泌涉及的电气事件，详细的表征 在此电流中，基础通道和信号通路 调节IAC活性对于理解肾上腺皮质至关重要 生理。 在拟议的研究中，牛和人类肾上腺Zona fasciculata中的IAC 将使用贴片电压夹技术检查细胞。功能 IAC在爪蟾卵母细胞中的表达将用于克隆IAC通道 cDNA。拟议研究的目的将是： 1）为生物物理特性表征IAC， 药理学和代谢因素和酶调节； 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 异武卵母细胞中的表达克隆。