The Unfolded Protein Response as an Organizer of Chemosensory Response

描述（由申请人提供）：嗅觉受体（OR）选择，数千种可用的哺乳动物OR等位基因之一的转录激活是一个知之甚少的过程。我们以前证明，在响应OR翻译，ER驻留激酶Perk磷酸化翻译起始因子eif2a，引发一个信号，最终在OR选择的稳定。遗传实验表明，这种反馈信号依赖于瞬时但普遍衰减的翻译和转录因子ATF 5的核同种型翻译的特异性上调。核ATF 5的产生增强腺苷酸环化酶3（Adcy3）的转录，其缓解OR诱导的ER应激并抑制组蛋白去甲基化酶LSD 1的表达，允许嗅神经元的终末分化并使所选择的OR的表达永久。这些观察结果提出了关于这个信号通路的分子原理的重要问题。在这里，我们提出的实验，试图提供这些问题的答案，并提供这种新的使用未折叠的蛋白质反应途径的机制的见解。具体来说，我们提出了生化和遗传实验，旨在揭示OR蛋白是否直接与Perk相互作用，并绘制负责Perk激活的确切肽。此外，我们的目标是阐明的作用机制，ATF5作为转录调节因子，并探讨两个不同的核亚型的功能，根据我们的初步遗传分析，发挥不同的作用，在调节或选择和分化的嗅觉神经元。最后，我们提出的实验，目的是解剖这个信号通路的结束步骤，这是ER应激的救济和OR诱导的Perk信号的终止。及时终止未折叠蛋白反应的这一臂对于OR表达的稳定和该途径的启动一样重要，我们假设OR特异性伴侣在防止ER中的OR-Perk相互作用中起关键作用。遗传和生物化学实验将揭示这些蛋白质的身份，并研究它们在OR引发的反馈中的作用。我们的实验将提供新的见解，一直是一个谜的过程，因为发现最大的哺乳动物基因家族，并将揭示可能适用于许多其他化学感受器家族介导的沟通与外界的监管原则。

DESCRIPTION (provided by applicant): Olfactory receptor (OR) choice, the transcriptional activation of one out of thousands of available mammalian OR alleles is a poorly understood process. We previously demonstrated that in response to OR translation, the ER-resident kinase Perk phosphorylates the translation initiation factor eif2a, eliciting a signal that culminates in the stabilization of OR choice. Genetic experiments suggest that this feedback signal depends upon the transient but general attenuation of translation and the specific upregulation of translation of the nuclear isoform of transcription factor ATF5. Production of nuclear ATF5 enhances the transcription of Adenylyl cyclase 3 (Adcy3), which relieves the OR-induced ER stress and represses the expression of histone demethylase LSD1, allowing the terminal differentiation of olfactory neurons and making the expression of the chosen OR permanent. These observations pose significant questions regarding the molecular principles of this signaling pathway. Here, we propose experiments that seek to provide answers to these questions and to offer mechanistic insight into this novel use of the unfolded protein response pathway. Specifically, we propose biochemical and genetic experiments aiming to reveal whether OR proteins interact directly with Perk and to map the exact peptides responsible for Perk activation. Furthermore, we aim to elucidate the mechanism of action of ATF5 as transcriptional regulator and to explore the function of two distinct nuclear isoforms that, according to our preliminary genetic analysis, play different roles in the regulation of OR choice and the differentiation of olfactory neurons. Finally, we propose experiments that aim to dissect the concluding step of this signaling pathway, which is the relief of ER stress and the termination of OR-induced Perk signaling. Timely termination of this arm of the unfolded protein response is as critical for the stabilization of OR expression as the initiation of this pathway an we hypothesize that OR-specific chaperones play a critical role in preventing OR-Perk interactions in the ER. Genetic and biochemical experiments will reveal the identity of these proteins and examine their role in the OR-elicited feedback. Our experiments will provide novel insight into a process that has remained enigmatic since the discovery the largest mammalian gene family and will reveal regulatory principles that likely apply to many other chemoreceptor families mediating communication with the outside world.