Molecular Basis of Sensory Transduction in C. elegans

描述（由申请人提供）：拟议研究的长期目标是了解引起触觉和振动感觉的分子和细胞事件。这些和其他机械感觉对于站立和行走以及控制膀胱功能和血压至关重要。机械转导是这些感觉的第一步，但仍然知之甚少。人们普遍认为，它依赖于响应于触摸中携带的机械能而打开的离子通道（所谓的机电转导或MeT通道）。在哺乳动物中形成MeT通道的蛋白质仍然未知。最近，我们证明了MEC-4和MEC-10是MeT通道的成孔亚基，负责C中对低强度触摸的敏感性。（O'Hagan等，2005，Nat Neurosci 8：43.）。既然C.由于线虫触觉感受器神经元是已知的，我们寻求以下关键问题的答案：1）力如何从身体表面转移到MeT通道，以及2）这些力如何导致通道开放。我们特别感兴趣的是了解触觉感受器神经元如何检测到小至100 nm的力，如何调整以主要响应力（振动）的变化，并在不到1毫秒的时间内响应刺激。提出了三个目标。首先，我们将确定膜变形是否足以激活重组C。elegans MeT通道（Aim 1），并探索这种敏感性（如果存在）可能依赖于MEC-4和MEC-10的第二跨膜结构域中存在的保守序列基序（Aim 2）的可能性。接下来，我们将确定MeT通道的体内激活是否涉及粘弹性元件，其可以在压缩期间充当能量存储装置（目的3）。最后，我们将研究微管和微管束在力传递和放大中的作用（目的4A），将体内电记录与微管束的超微结构分析配对，并研究微管和肌动蛋白结合蛋白对力传递的贡献。我们还建议开发和部署新的设备，用于控制机械刺激（力和位移）的应用，并用于测量自由移动C产生的力。蠕虫这项研究结合了我们在感觉生物物理学方面的独特专长，从确定的C。线虫神经元，遗传分析和超微结构研究，以获得对触觉的深刻理解。从这些研究中学到的东西有可能提高对疾病和正常衰老中触觉和功能障碍的理解。公共卫生相关性：触觉和振动感在正常衰老和慢性疾病（如糖尿病）中受到损害。最近的估计表明，由于糖尿病和年龄相关的触摸和振动感觉功能障碍，每年的健康成本超过280亿美元。该提案旨在通过研究蛔虫C来提高对触觉的理解。它是一种简单的动物，其触觉比我们人类的触觉研究得更好。从这项研究中学到的东西有可能为触觉退化的可能诊断工具和治疗提供新的见解。

DESCRIPTION (provided by applicant): The long-term objective of the proposed research is to understand the molecular and cellular events that give rise to the senses of touch and vibration. These and other mechanical senses are critical for standing and walking as well as the control of bladder function and blood pressure. Mechanotransduction is the first step in each of these senses, but remains poorly understood. It is widely believed to rely on ion channels (so-called mechano-eletrical transduction or MeT channels) that open in response to the mechanical energy carried in a touch. The proteins that form MeT channels in mammals remain unknown. Recently, we demonstrated that MEC-4 and MEC-10 are pore-forming subunits of the MeT channel responsible for sensitivity to low-intensity touch in C. elegans (O'Hagan et al, 2005, Nat Neurosci 8: 43.). Now that the molecular identity of the MeT channel in C. elegans touch receptor neurons is known, we seek answers to the key questions of 1) how force is transferred from the body surface to MeT channels and 2) how such forces lead to channel opening. We are particularly interested in understanding how touch receptor neurons detect forces as small as 100nm, are tuned to respond primarily to changes in force (vibration) and respond to stimulation in less than 1 millisecond. Three aims are proposed. First, we will determine whether or not membrane deformation is sufficient to activate recombinant C. elegans MeT channels (Aim 1) and explore the possibility that such sensitivity, if present, might rely on a conserved sequence motif present in the 2nd transmembrane domain of MEC-4 and MEC-10 (Aim 2). Next, we will determine if in vivo activation of MeT channels involves visco-elastic elements that could act as energy storage devices during compression (Aim 3). Finally, we will investigate the role of microtubules and the microtubule bundle in force transfer and amplification (Aim 4A), pairing in vivo electrical recording with ultrastructural analysis of the microtubule bundle and investigate the contribution of microtubule- and actin- binding proteins to force transfer. We also propose to develop and deploy new devices for controlled application of mechanical stimuli (both force and displacement) and for measuring forces generated by freely moving C. elegans worms. The proposed research combines our unique expertise in sensory biophysics, in vivo electrical recording from identified C. elegans neurons, genetic analysis, and ultrastructural studies to derive a profound understanding of the sense of touch. What is learned from these studies has the potential to improve understanding of touch sensation and dysfunction in disease and normal aging. PUBLIC HEALTH RELEVANCE: The senses of touch and vibration are compromised in normal aging and by chronic diseases such as diabetes. Recent estimates suggest that the health costs due to diabetes- and age-related dysfunction of touch and vibration sensation are more than $28 billion annually. This proposal seeks to improve understanding of touch sensation by studying the roundworm C. elegans, a simple animal whose sense of touch is better studied than our own. What is learned from this research has the potential to provide new insight into possible diagnostic tools and treatments for the degradation of touch sensation.