Structural Mechanism for Gating of Mechanosensitive Channels

摘要 机械敏感通道门控的结构机理 由机械敏感通道介导的机械力感觉是一系列基本的 生理过程，包括听觉、触觉、本体感觉、渗透调节和形态发生。 力觉障碍与许多疾病有关，包括耳聋、动脉粥样硬化、 慢性疼痛和癌症。原核生物机械敏感小电导通道(MSCs)的保护作用 细菌细胞在低渗下激波下破裂。多种MSCs样通道，存在于许多 包括细菌、真菌、藻类和植物在内的有机体形成了一个异常多样的航道超级家族 这对渗透压的管理至关重要。动物体内缺乏间充质干细胞同源物，因此 在细菌和真菌等致病微生物中靶向MSCs通道可能导致新的 抗菌治疗策略。目前的机械论理解，主要是从对 典型的原核通道，E.Coli MSCs，仍然是有限的。结构、生化和生物物理 真核间充质干细胞通道和多结构域原核生物等复合膜蛋白的分析 事实证明，MSCs同源物具有挑战性，因为在生产足够大量的 生化稳定的蛋白质样本。通过最近的事态发展，我们克服了这些关键障碍 在大规模蛋白质生产中对多种MSCs家族成员的结构和功能分析 具有不同的膜拓扑和结构域组织。我们最近对A的结构和功能进行了研究 真核细胞通道MSL1发现了一种“扁平和扩张”的门控机制，源于一种 静息状态的非平面跨膜区，这让人想起进化和 在建筑上无关的哺乳动物机械敏感的压电通道。这些结果导致了我们的中央 假设跨膜区的“扁平和扩张”可能是一种统一的门控机制。 有了这些令人兴奋的发展，我们现在能够结合结构生物学和电生理学来 解决机械生物学中的一个核心问题：机械敏感通道是如何开启的？ 具体地说，我们的目标是揭示具有不同膜的不同MSCs通道的门控转换 以进一步评估这一潜在的通用门控机制。详细了解 机制将提供关键信息，最终将导致新抗菌剂的开发 与机械改变相关的多种疾病的试剂和新的治疗策略 强力感。

ABSTRACT Structural Mechanism for Gating of Mechanosensitive Channels Mechanical force sensation mediated by mechanosensitive channels underlies an array of fundamental physiological processes, including hearing, touch, proprioception, osmoregulation, and morphogenesis. Dysfunctional force sensation is associated with numerous diseases including deafness, atherosclerosis, chronic pain and cancer. The prokaryotic mechanosensitive channel of small conductance (MscS) protects bacterial cells from rupture under hypoosmotic downshock. A variety of MscS-like channels, found in many organisms including bacteria, fungi, algae, and plants, form an exceptionally diverse superfamily of channels that are crucial for management of osmotic pressure. MscS homologs are absent in animals, and thus targeting MscS channels in pathogenic microorganisms such as bacteria and fungi could lead to new antimicrobial treatment strategies. Current mechanistic understanding, primarily inferred from studies of the prototypical prokaryotic channel, E. Coli MscS, remains limited. Structural, biochemical, and biophysical analyses of complex membrane proteins such as eukaryotic MscS channels and multi-domain prokaryotic MscS homologs have proven challenging owing to major difficulties in producing sufficiently large quantities of biochemically stable protein samples. We have overcome these critical barriers through recent developments in large-scale protein production and structural and functional analyses of a variety of MscS family members with distinct membrane topologies and domain organizations. Our recent structural and functional studies of a eukaryotic channel MSL1 have uncovered a `flattening and expansion' gating mechanism stemming from a non-planar transmembrane domain at the resting state, which is reminiscent of the evolutionarily and architecturally unrelated mammalian mechanosensitive Piezo channels. These results lead to our central hypothesis that `flattening and expansion' in the transmembrane region may be a unifying gating mechanism. With these exciting developments, we are now able to combine structural biology and electrophysiology to address one of the central questions in mechanobiology: how do mechanosensitive channels gate? Specifically, we aim to reveal gating transitions of a diverse set of MscS channels with distinct membrane topologies to further evaluate this potentially universal gating mechanism. Detailed understanding of the mechanisms will provide critical information that will ultimately lead to development of new antimicrobial reagents and new treatment strategies for a broad spectrum of diseases associated with altered mechanical force sensation.