PROPERTIES OF A K+ CURRENT THAT CONTROLS SECRECTION

控制节流的 AK 电流的特性

• 批准号: 6624887
• 负责人: JOHN J ENYEART
• 金额: $ 17.52万
• 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 2004-09-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6624887
• 关键词: G protein; adenosine triphosphate; adrenal glands; adrenocorticotropic hormone; angiotensin II; bioenergetics; biological signal transduction; cortisol; hormone regulation /control mechanism; leptin; molecular cloning; nucleic acid sequence; pituitary adrenal axis; potassium channel; secretion; tissue /cell culture; voltage /patch clamp

In mammals, adrenal zona fasciculata (AZF) cells secrete cortisol which acts on cells of the liver, muscle, and adipose tissue to enhance glucose synthesis and to promote the breakdown of fat and muscle proteins. Precise control of blood glucose concentration by cortisol and other hormones is critical because this sugar is the primary energy source for the brain. Hypoglycemia can cause brain damage or death. Aberrant corticosteroid secretion is responsible for Cushing's and Addison's diseases. Cortisol secretion is controlled primarily by the pituitary peptide ACTH. However, a number of other physiological factors, including Angiotensin II, leptin, nucleotides, epinephrine, and glucose act on AZF cells to regulate secretion of this hormone. While physiological stimuli that regulate cortisol secretion have been identified, the signalling pathways involved are not understood. Although, the release of many hormones is coupled to depolarization-dependent Ca+ entry, the function of specific ion channels in AZF cell secretion has not been clarified. Bovine AZF calls express a novel K+ current (I[AC]) that sets the resting potential while it is inhibited by ACTH, AII, and external ATP at concentrations identical to those that depolarize AZF cells and stimulate cortisol secretion. These channels are also directly activated by intracellular ATP. The Convergent inhibition of I[AC] by three G protein- coupled receptors and its activation by intracellular ATP suggest that this channel is a control point where hormonal and metabolic signals are integrated and transduced to permeability and membrane potential changes associated with cortisol secretion. A detailed characterization of this channel, and the signalling pathways that regulate its activity will be essential to an understanding of adrenal cortical physiology. Whole-cell and single channel patch clamp will be used to describe the modulation of I[AC] K+ channels by hormones and metabolic factors. The aims of the proposed research will be: (1) to determine whether I[AC] channel gating is coupled to an ATP hydrolysis cycle, allowing these channels to act as glucose sensors; (2) to determine whether other hormonal and paracrine factors which physiologically regulate cortisol secretion, also modulate I[AC] K+ channels; (3) to identify the molecular components of the signalling pathway by which ACTH inhibits I[AC]; and (4) to characterize the properties and distribution of I[AC] K+ channel cDNAs after cloning and expression in a eucaryotic cell line.

在哺乳动物中，肾上腺Zona筋膜（AZF）细胞分泌皮质醇，该细胞作用于肝脏，肌肉和脂肪组织的细胞上，以增强葡萄糖合成并促进脂肪和肌肉蛋白的分解。皮质醇和其他激素对血糖浓度的精确控制至关重要，因为该糖是大脑的主要能源。低血糖会导致脑损伤或死亡。异常的皮质类固醇分泌造成库欣和艾迪生的疾病。皮质醇分泌主要由垂体肽ACTH控制。然而，许多其他生理因素，包括血管紧张素II，瘦素，核苷酸，肾上腺素和葡萄糖作用于AZF细胞，以调节这种激素的分泌。尽管已经确定了调节皮质醇分泌的生理刺激，但涉及的信号通路尚不清楚。虽然，许多激素的释放与去极化依赖性CA+进入，但尚未阐明特定离子通道在AZF细胞分泌中的功能。牛AZF调用表达了一种新型的K+电流（I [AC]），该电流（I [AC]）在ACTH，AII和外部ATP抑制静止电位的同时，浓度与去极性AZF细胞并刺激皮质醇分泌的浓度相同。这些通道也通过细胞内ATP直接激活。三个G蛋白偶联受体对I [AC]的融合抑制作用及其在细胞内ATP激活表明，该通道是一个控制点，在该控制点集成了激素和代谢信号，并将其转化为渗透性和与皮质醇分泌有关的渗透性和膜电势变化。该通道的详细表征以及调节其活性的信号传导途径对于理解肾上腺皮质生理学至关重要。全细胞和单个通道斑块夹将使用激素和代谢因子来描述I [AC] K+通道的调制。拟议的研究的目的是：（1）确定I [AC]通道门控是否耦合到ATP水解周期，从而使这些通道充当葡萄糖传感器； （2）确定生理调节皮质醇分泌的其他激素和旁分泌因子是否也调节I [AC] K+通道； （3）确定ACTH抑制I [AC]的信号传导途径的分子成分； （4）在克隆和表达桉树细胞系中表征I [AC] K+通道CDNA的性质和分布。