RETROGRADE TROPHIC SIGNALING THROUGH ACETYLCHOLINE RECEPTORS AT THE NEUROMUSCULA

项目摘要(见说明)：项目3的摘要：在之前的资助期间，我们意外地发现，小泡(微型终板电流，MEPCS)的自发释放在调节小鼠神经肌肉接头(NMJ)的可释放小泡(N)数量方面发挥着重要作用。在初步研究中，我们发现在体外NMJ制剂中，减少MEPCS中乙酰胆碱与乙酰胆碱受体(AChRs)的结合会在几分钟内触发n的增加。我们的初步数据表明，这是由于肌肉上AChRs开放引起的逆行信号的改变。综上所述，我们的发现表明，存在来自肌肉的持续逆行信号，这种信号以一分钟为一分钟的时间尺度来调节运动神经元的突触前功能。我们使用体外制剂可以对这一正在进行的信号进行详细研究，而这在体内是不可能的。在这项提案中，我们将使用体内和体外研究来剖析这一途径背后的分子信号。更好地理解这一途径将对理解突触可塑性和运动神经元对损伤的反应，包括兴奋性的变化和突触输入的丢失具有重要意义。我们假设，我们在NMJ研究的营养信号通路的中断是导致周围神经损伤后潜在的适应不良脊髓可塑性的触发因素。我们的发现可能对运动神经元疾病、脊髓性肌萎缩症以及神经肌肉疾病重症肌无力有意义。

PROJECT SUMMARY (See Instructions): Summary for Project 3: During the previous grant period we made the unexpected finding that spontaneous release of vesicles (miniature endplate currents, MEPCs) plays an important role in regulating the number of releasable vesicles (n) at the mouse neuromuscular junction (NMJ) in vivo. During preliminary studies we found that reducing the binding of acetylcholine to acetylcholine receptors (AChRs) during MEPCs in an ex vivo NMJ preparation triggers an increase in n within minutes. Our preliminary data suggests this is due to alteration of a retrograde signal initiated by opening of AChRs on muscle. Taken together our findings suggest there is a continuous retrograde signal from muscle that operates on a minute by minute time scale to adjust presynaptic function of the motoneuron. Our use of an ex vivo preparation allows for detailed study of this ongoing signaling that is not possible in vivo. In this proposal we will use both in vivo and ex vivo studies to dissect the molecular signaling underlying this pathway. A better understanding of this pathway will have implications for understanding synaptic plasticity and the response of motoneurons to injury including changes in excitability and loss of synaptic inputs. We hypothesize that disruption of the trophic signaling pathway we are studying at the NMJ is a trigger that induces potentially maladaptive spinal cord plasticity following peripheral nerve injury. Our findings could have implications for the motoneuron disease spinal muscular atrophy as well as the neuromuscular disease myasthenia gravis.