Desensitization of Nicotinic Acetylcholine Receptors

神经-肌肉突触处的烟碱型乙酰胆碱受体（AChRs）进入并恢复 在神经递质持续存在的情况下保持不活动的状态。 受体脱敏下调细胞反应并编码长期活动模式。 我们的目标是在分子水平上了解AChR脱敏过程。的基本 D状态如何连接到C（关闭）和O（未关闭）选通状态的问题仍然没有解决。 我们将研究两个假设：i）D，O和C连接在一个封闭的循环中，ii）D不是 连接到C或O，而是一个短暂的门控中间状态。我们将测试 第二个假设实验通过使用突变和电压来转移点， 门控和脱敏构象变化途径之间的分歧，对C， 在恢复或朝向O时产生开口以防止开口。许多氨基酸改变 在AChR门控和脱敏过渡期间，这些微观结构中的每一个都是 重排具有相关联的且主要是局部的自由能变化。我们将测量这些 AChR跨膜结构域中两个区域的脱敏能量变化：i）a M1中的脯氨酸扭结和ii）疏水性M2门。尽管深入调查， AChR脱敏的分子基础一直不清楚， 描述了60年前。这项提案中的实验将填补我们在这方面的重大空白。 了解受体的运作。

Nicotinic acetylcholine receptors (AChRs) at the nerve-muscle synapse enter and recover from D(esensitized) states that remain inactive in the continuous presence of neurotransmitter. Receptor desensitization down-regulates cell responses and encodes long-term activity patterns. Our goal is to understand the AChR desensitization process at a molecular level. The essential problem of how D states are connected to C(losed) and O(pen) gating states remains unsolved. We will investigate two hypotheses: i) D, O and C are connected in a closed cycle and ii) D is not connected either to C or O but rather to a short-lived gating intermediate state. We will test the second hypothesis experimentally by using mutations and voltage to shift the point of bifurcation between gating and desensitization conformational-change pathways, towards C to produce openings upon recovery or towards O to prevent openings. Many amino acids change structure during the AChR gating and desensitization transitions, and each of these microscopic rearrangements has an associated and mostly-local free energy change. We will measure these energy changes in desensitization at two regions in the AChR transmembrane domain: i) a proline kink in M1 and ii) the hydrophobic M2 gate. Despite intensive investigation, the molecular basis of AChR desensitization has remained obscure since the process was first described 60 years ago. The experiments in this proposal will fill this substantial gap in our understanding of receptor operation.