Characterizing the role of TRPM4 in taste transduction

化学感觉系统是由嗅觉和味觉组成的，在脊椎动物和许多无脊椎动物的进食和社会交往中起着重要作用。味觉被用来决定潜在的食物是否会被摄入或拒绝，对生物体的生存至关重要。因为激活味觉系统的化学物质具有不同的结构，所以有多种味觉细胞类型使用不同的信号通路来检测这些刺激。一些味觉化学物质激活受体，启动第二信使级联反应，而另一些则直接与离子通道相互作用，引起细胞反应。PI的实验室最近报告说，单价选择性TRP通道TRPM4在味觉传导中起着关键作用，但它在味觉细胞中的功能尚不清楚。本应用的目的是表征TRPM4如何在不同的信号通路中促进味觉转导。总的来说，目前对将味觉刺激转化为信号并发送到大脑进行处理的基本机制的理解仍然非常有限。因此，更好地描述这些信号通路将有助于我们更好地理解味觉信息是如何被发送到大脑的，更广泛地说，有助于我们了解大脑是如何收集周围环境信息的。该项目还将支持PI的努力，通过布法罗大学的大学科技入门计划（CSTEP）增加代表性不足的群体在STEM领域从事职业的人数。味觉刺激激活口腔内不同味觉细胞群的多种信号传导机制。一个细胞群通过常规突触进行交流，并表达电压门控钙通道（VGCCs）。不同的细胞群缺乏化学突触，依赖于磷脂酶c依赖的信号通路来激活Calhm1/3通道复合物来释放神经递质。表达这种途径的味觉细胞（称为II型细胞）有助于检测苦味、甜味和鲜味的味觉刺激。具有传统突触的味觉细胞（III型细胞）检测酸味和咸味刺激。最近，越来越清楚的是，这些不同细胞类型的信号通路比以前认识到的要复杂得多。PI的实验室确定了瞬时受体电位美拉他汀4通道（TRPM4）在II型信号通路中的关键作用，并报道TRPM4也在III型细胞中表达。初步数据发现，TRPM4的作用在不同的信号通路中是不同的，并且不同地用于影响输出响应。这是如何发生的以及在这些不同细胞群中调节TRPM4活性的调节剂是未知的。该提案的重点是定义TRPM4在不同味觉信号通路中的功能，并确定其在每种通路中的调节方式。具体目的是：(1)在II型细胞中，TRPM4在GPCR信号通路中是如何调控的？(2) TRPM4在III型细胞嗜离子信号传导中的作用是什么？这些目标将通过小鼠转基因、活细胞成像和药理学方法来实现。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Chemical sensory systems, which are comprised of olfaction and taste in vertebrates and many invertebrates, play important roles in feeding and social interactions. The sense of taste is used to determine whether potential food items will be ingested or rejected and is critical for an organism’s survival. Because the chemicals that activate the taste system have variable structures, there are multiple taste cell types that use different signaling pathways to detect these stimuli. Some taste chemicals activate receptors that initiate second messenger cascades, while others interact directly with ion channels to cause a cellular response. The PI’s laboratory has recently reported that the monovalent selective TRP channel, TRPM4, has a critical role in taste transduction but how it functions in taste cells is poorly understood. The goal of this application is to characterize how TRPM4 contributes to taste transduction in the different signaling pathways. Overall, the current understanding of the fundamental mechanisms that translate taste stimuli into a signal that is sent to the brain for processing is still quite limited. Therefore, a better characterization of these signaling pathways will provide an enhanced understanding of how taste information is sent to the brain and more generally, provide new insights into how the brain gathers information about its surroundings. The project will also support the PI's efforts to increase the number of underrepresented groups to pursue careers in STEM through the University at Buffalo’s Collegiate Science and Technology Entry Program (CSTEP).Taste stimuli activate multiple signaling mechanisms in distinct taste cells populations within the oral cavity. One cell population communicates via conventional synapses and expresses voltage-gated calcium channels (VGCCs). A different cell population lacks chemical synapses and relies on the phospholipase-C-dependent signaling pathway to activate a Calhm1/3 channel complex to release neurotransmitter. Taste cells that express this pathway (called Type II cells) contribute to the detection of bitter, sweet and umami taste stimuli. Taste cells with conventional synapses (Type III cells) detect sour and salty stimuli. Recently, it is becoming clear that the signaling pathways in these different cell types are more complex than previously appreciated. The PI’s laboratory identified a critical role for the transient receptor potential melastatin 4 channel (TRPM4) in the Type II signaling pathways and reported that TRPM4 is also expressed in Type III cells. Initial data has found that the role of TRPM4 varies within the different signaling pathways and is differentially used to affect the output response. How this happens and the modulators regulating TRPM4 activity in these different cell populations is unknown. The proposal’s focus is to define the function of TRPM4 in different taste signaling pathways and to identify how it is regulated in each. The specific aims are: (1) How is TRPM4 regulated in the GPCR signaling pathway in Type II cells? and (2) What is the role of TRPM4 in ionotropic signaling in Type III cells? These aims will be accomplished using mouse transgenics, live cell imaging and pharmacological approaches.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.