Inflammatory hyperalgesia due to TRPV1, the pepper spray receptor in the cornea

描述（由申请人提供）：我们工作的目标是阐明细胞表面受体调节离子通道功能、运输和表达的细胞和分子机制。我们对疼痛传导中离子通道的受体调节特别感兴趣，因为炎症期间对疼痛刺激的敏感性（炎症性痛觉过敏）深刻地影响着我们的身心健康，以及我们的经济和社会福祉。我们选择了Ca 2+渗透通道TRPV 1作为我们的模型，因为它的特性使其特别适合，因为它在传递疼痛刺激和调节疼痛传递神经元的兴奋性方面的重要性。慢性疼痛在美国是一个重要的公共卫生和经济问题。2003年美国生产力审计的一项分析显示，在给定的两周时间内，13%的劳动力因无法控制的疼痛而失去工作时间，平均每周损失4.6小时。2003年国家卫生统计中心的报告发现，26%的成年人报告有持续超过24小时的疼痛问题。2006年的一项针对慢性疼痛患者的研究发现，超过一半的人感到他们对疼痛几乎没有控制力。头痛，背痛，关节炎疼痛，牙痛，癌症疼痛和术后疼痛只是导致整个美国人口生活质量下降和经济损失的常见疾病中的一小部分。目前的治疗方法显然不足以解决广泛的疼痛缓解需求，并且存在与特异性和成瘾性相关的进一步问题。神经生长因子（Nerve Growth Factor，NGF）是由Rita Levi-Montalcini和Stanley Cohen在20世纪50年代末发现的。从一开始，他们就理解了它调节感觉神经元分化和生长的能力。NGF参与感觉神经元的引导和存活，并在损伤和炎症期间释放到表达TRPV 1的神经元上。在过去的几年里，我们对NGF如何在炎性痛觉过敏中使TRPV 1增敏的理解激增。在之前的资助期间，我们发现NGF通过增加质膜中TRPV 1通道的数量来增加TRPV 1电流。我们进一步表明，在伤害感受器中存在一种信号转导复合物，由NGF受体（TrkA）、TRPV 1和酶PI 3 K组成，该酶将磷酸肌醇4，5-二磷酸（PIP 2）磷酸化为磷酸肌醇3，4，5-三磷酸（PIP 3）。我们和其他人进一步表明，PI 3 K活性是致敏所必需的。对于本提案的其余部分，使用术语TRPV 1的“致敏”来指质膜中TRPV 1通道数量的增加。虽然细胞表面受体刺激的膜脂和膜蛋白的运输对生物学具有广泛的意义，但对其发生的分子机制知之甚少。研究得最好的例子之一，运输的Glut 4葡萄糖转运蛋白的脂肪细胞和肌肉细胞的质膜响应胰岛素，揭示了一些重要的球员，我们基于我们的模型为神经生长因子诱导的运输TRPV 1的疼痛受体神经元的质膜。然而，即使在脂肪细胞和肌肉中，这个过程中的许多关键步骤也没有完全理解。识别TRPV 1致敏的主要参与者及其相互作用可能会揭示细胞分化，代谢和生存所必需的信号通路，以及对炎症性疼痛重要的TRPV 1调节的理解。

DESCRIPTION (provided by applicant): The goal of our work is to elucidate the cellular and molecular mechanisms by which cell-surface receptors regulate the function, trafficking, and expression of ion channels. We are particularly interested in receptor regulation of ion channels in pain transduction, as sensitization to painful stimuli during inflammation (inflammatory hyperalgesia) profoundly influences our physical and mental health, as well as our economic and social well-being. We have chosen the Ca2+-permeable channel TRPV1 as our model both because its properties make it especially suitable and because of its importance in transducing painful stimuli and in tuning the excitability of pain-transducing neurons. Chronic pain is a significant public health and economic problem in the US. An analysis of the 2003 American Productivity Audit, a national survey of US workers, showed that, in a given two-week period, 13% of the workforce lost work time due to uncontrolled pain, with a mean loss of 4.6 hours per week. The 2003 National Center for Health Statistics Report found that 26% of adults report having a problem with pain lasting more than 24 hours. A 2006 study of chronic pain patients found that more than half felt they had little or no control over their pain. Headache, back pain, arthritis pain, tooth pain, cancer pain, and post-operative pain are just a few of the common conditions contributing to decreased quality of life and economic loss across the whole spectrum of the US population. Current treatments are clearly not sufficient to address the wide-spread need for pain relief, and have further problems related to specificity and addiction. Nerve Growth Factor (NGF) was discovered by Rita Levi-Montalcini and Stanley Cohen in the late 1950's. From the first, they understood its power to regulate the differentiation and growth of sensory neurons. NGF is involved in the guidance and survival of sensory neurons and is released onto TRPV1-expressing neurons during injury and inflammation. Our understanding of how NGF sensitizes TRPV1 in inflammatory hyperalgesia exploded in the last several years. In the previous funding period we showed that NGF increases TRPV1 currents by increasing the number of the TRPV1 channels in the plasma membrane. We further showed that a signal-transduction complex is present in nociceptors, composed of the NGF receptor (TrkA), TRPV1, and the enzyme PI3K, which phosphorylates phosphoinositide 4,5-bisphosphate (PIP2) to phosphoinositide 3,4,5-trisphosphate (PIP3). We and others further showed that PI3K activity is required for sensitization. For the remainder of this proposal use the term "sensitization" of TRPV1 to refer to the increase in the number of TRPV1 channels in the plasma membrane. Although cell surface receptor-stimulated trafficking of membrane lipids and membrane proteins is of broad significance to biology, the molecular mechanisms by which it occurs are poorly understood. One of the best-studied examples, trafficking of the Glut4 glucose transporter to the plasma membrane of adipocytes and muscle cells in response to insulin, has revealed a number of important players on which we based our model for NGF-induced trafficking of TRPV1 to the plasma membrane of pain-receptor neurons. Even in adipocytes and muscles, however, many critical steps in this process are not fully understood. Identification of the main players and their interactions in sensitization of TRPV1 may shed light on a signaling pathway essential to cell differentiation, metabolism, and survival in addition to leading to an understanding of TRPV1 regulation important for inflammatory pain.