NEURAL FACTORS AND UPPER AIRWAY MUSCLE DEVELOPMENT

神经因素和上呼吸道肌肉发育

• 批准号: 6196306
• 负责人: DAVID E MILLHORN
• 金额: $ 30.6万
• 依托单位: UNIVERSITY OF CINCINNATI
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-07-10 至 2004-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6196306
• 关键词: cell line; developmental neurobiology; enzyme activity; genetically modified animals; hormone regulation /control mechanism; immunoprecipitation; laboratory mouse; motor neurons; neural conduction; neuromuscular junction; newborn animals; nicotinic receptors; protein kinase; protein structure function; protein tyrosine phosphatase; pulmonary respiration; respiratory muscles; somatostatin; voltage /patch clamp; western blottings

Breathing is a highly regulated process that requires precise coordination among the muscles that cause ventilation and those responsible for maintenance of upper airway patency. Failure to properly activate the upper airway dilator muscles in response to an increase in inspiratory drive can result in obstruction of the upper airways. High fidelity synaptic signaling across the neuromuscular junction is required for precise regulation of upper airway patency that corresponds to the level of inspiratory drive. The major synaptic component of the neuromuscular junction is the nicotinic acetylcholine receptor (nAChR), a ligand (ACh)- gated channel that is composed of four homologous trans-membrane subunits (alpha2, beta, epsilon, gamma) arranged in a pentamer. During early postnatal development the nAChR undergoes a structural modification which impacts on its ability to respond to ACh released from motoneurons. In the neonate, the nAChR contains a gamma- instead of the epsilon-subunit. The nAChR-gamma exhibits a lower single channel conductance than the adult nAChR-epsilon. Thus, muscles that express more nACh-gamma and less nAChR-epsilon might be prone to hypotonicity and less responsive to synaptic input. We hypothesize that discordant regulation of the nAChR-gamma and nAChR-epsilon isoforms could lead to reduced upper airway patency and airway obstruction There is growing evidence that opposing kinase and phosphatase pathways in muscle regulate the nAChR-gamma to nAChR-epsilon transition during early postnatal development. Moreover, recent findings indicate that both the kinase and phosphatase activities are regulated by "trophic" factors released from the motoneurons. The proposed research will investigate the role of the tetradecapeptide somatostatin (SST) in the regulation of tyrosyl phosphatase (PTPase) activities in muscle. Preliminary results show that SST, which is expressed developmentally in the motoneurons that innervate the upper airways, prevents induction of -subunit gene expression by the kinase pathway. The specific aims are: 1) Identify and characterize the protein tyrosyl phosphatases that are activated by SST and cause inhibition of epsilon-subunit gene expression; 2) Determine the mechanism by which SST-induced PTPases oppose kinase pathways to prevent activation of epsilon-subunit gene expression; and 3) Determine the effect of continuous expression of the SST-SSTR-PTPase pathway on epsilon-subunit gene expression in genetically engineered mice.

呼吸是一个高度受监管的过程，需要引起呼吸的肌肉和负责维持上呼吸道通畅的肌肉之间的精确协调。吸气动力增加时，未能正确激活上呼吸道扩张器肌肉，可能会导致上呼吸道阻塞。通过神经肌肉接头的高保真突触信号是精确调节上呼吸道通畅性所必需的，这与吸气驱动的水平相对应。神经肌肉接头的主要突触成分是烟碱型乙酰胆碱受体(NAChR)，这是一种配体(ACh)门控通道，由四个同源跨膜亚基(α2，β，epsilon，Gamma)组成，排列成五聚体。在出生后早期发育过程中，nAChR经历了一种结构改变，这影响了它对运动神经元释放的ACh的反应能力。在新生儿中，nAChR含有一个伽马亚基，而不是epsilon亚基。NAChR-Gamma的单通道电导低于成年nAChR-epsilon。因此，表达较多nACH-γ和较少nAChR-epsilon的肌肉可能倾向于低张，对突触输入的反应较差。我们推测，nAChR-γ和nAChR-epsilon亚型的不协调调节可能导致上呼吸道通畅和气道阻塞的减少。越来越多的证据表明，肌肉中相反的激酶和磷酸酶途径调节着nAChR-γ到nAChR-epsilon的转变。此外，最近的发现表明，激酶和磷酸酶的活性都受到运动神经元释放的营养因子的调节。这项拟议的研究将探讨十四肽生长抑素(SST)在肌肉中酪氨酸磷酸酶(PTPase)活性调节中的作用。初步结果表明，在支配上呼吸道的运动神经元中发育表达的SST阻止了由激酶途径诱导的-亚单位基因的表达。其具体目的是：1)鉴定和鉴定SST激活并导致epsilon亚单位基因表达抑制的蛋白酪氨酸磷酸酶；2)确定SST诱导的PTPase对抗激酶通路以防止epsilon亚单位基因表达的机制；以及3)在基因工程小鼠中确定SST-SSTR-PTPase途径的持续表达对epsilon亚单位基因表达的影响。