Genetic Analysis of Nociception in Drosophila

描述(由申请人提供)：了解体感信号通路的分子机制对于寻找新的减轻疼痛的方法至关重要。为了发现新的伤害感受途径，我们采用了一种先进的遗传方法，使用果蝇黑腹果蝇。利用幼虫对伤害性刺激的行为反应，我们已经在无痛基因中鉴定出在机械和热伤害感受方面存在缺陷的突变。无痛神经元表达于多树突状神经元，其形态类似于脊椎动物的伤害性神经元，在表皮下有多个分支的裸露神经突起。这种无痛蛋白是瞬时受体电位离子通道家族的成员，其中许多与温度转导和机械转导有关。在果蝇中，有三个TRPA通道被认为是温度敏感器；无痛通道，我们在遗传学上发现它与热伤害性有关，果蝇TRPA1(DTRPA1)通道与热趋向性有关，第三个通道名为高热，它提供对热应激的抗性。虽然色氨酸通道在热敏和机械信号转导中的作用是显而易见的，但通过这些通道调节对温度和机械刺激的反应的分子机制仍然是一个谜。我们非常适合使用体内遗传学来了解色氨酸通道在机械转导和热转导中作用的基本原理。我们将检验三个假设：1)果蝇TRPA通道联合决定果蝇幼虫的热伤害性阈值；2)果蝇多树突状感觉神经元的一个特定亚类在伤害性感受中发挥作用；3)无痛通道的Ankyrin重复结构域对于机械转导是必不可少的。这些研究将提供对伤害性感受的分子和细胞机制的洞察，这将有助于开发治疗疼痛的干预措施。

DESCRIPTION (provided by applicant): Understanding molecular mechanisms of somatosensory signaling pathways is critical to find new methods of alleviating pain. To discover novel nociception pathways, we have taken a forward genetic approach using the fruitfly Drosophila melanogaster. Using a larval behavioral response to noxious stimuli we have identified mutants in the painless gene that are defective in mechanical and thermal nociception. Painless is expressed in multidendritic neurons which morphologically resemble vertebrate nociceptive neurons having multiply branched naked neurites beneath the epidermis. The Painless protein is a member of the Transient Receptor Potential family of ion channels, many of which have been implicated in temperature transduction and in mechanotransduction. In Drosophila, three TRPA channels have been implicated as thermosensors; the Painless channel, which we identified genetically as required for thermal nociception, the Drosophila TRPA1 (dTRPAl) channel which has been implicated in thermotaxis, and a third channel named Pyrexia that provides resistance to thermal stress. While it is clear that TRP channels can function in thermosensory and mechanical signal transduction, the molecular mechanisms responsible for mediating responses to temperature and mechanical stimuli by these channels are still a mystery. We are ideally positioned to use in vivo genetics to understand the basic principles underlying TRP channel function in mechanotransduction and in thermotransduction. We will test three hypotheses: 1) that Drosophila TRPA channels combinatorially determine the thermal nociception threshold of the Drosophila larva; 2) that a specific subclass of Drosophila multidendritic sensory neuron functions in nociception; and 3) that ankyrin repeat domains of the Painless channel are essential for mechanotransduction. These studies will provide insight into molecular and cellular mechanisms of nociception that will assist in developing therapeutic interventions for the treatment of pain.