Analysis of MuSK functions and the molecular pathogenesis of myasthenia gravis with anti-MuSK autoantibodies by proteomic approaches

我们首次在可检测到AChR自身抗体(血清阳性MG)的全身性重症肌无力(MG)中鉴定出抗Musk自身抗体，并在《神经学》杂志上报道(2004年出版)。此前，Hoch等人。2001年在MG中发现了一种新的抗原--马斯克，但没有检测到AChR自身抗体(血清阴性MG)。因此，我们可以为研究麝香的功能和由麝香自身抗体引起的泛发性MG的分子发病机制提供一个新的范围。接下来，我们可以通过免疫麝香蛋白来产生麝香自身抗体，从而诱导兔出现类MG肌无力。然后，我们发现了明确的证据，表明这些麝香抗体特异性地抑制了对所有已知刺激的AChR聚集反应，包括那些与集聚蛋白无关的途径。Agrin通过激活麝香诱导AChR聚集，而agrin非依赖性刺激物不能。也就是说，穆斯克自身抗体严格抑制多途径介导的AChR聚集，这一结果拓宽了对MG发病机制的一般理解(2004年提交发表)。最后，我们制备了大量用于蛋白质结构分析的穆斯克蛋白。我们现在正在筛选最佳的结晶条件，以便使用哈里马-理研的同步加速器(Spring-8)分析结构。此外，我们现在正在分析麝香-乳胶敲入小鼠，以阐明麝香在生物体中的功能。

We firstly identified anti-MuSK autoantibodies in generalized myasthenia gravis(MG) with detectable AChR autoantibodies(seropositive MG) and reported in Nurology(in press, 2004). Previously, Hoch et al. found a novel antigen, MuSK in MG without detectable AChR autoantibodies(seronegative MG) in 2001. Therefore we could provide a new scope for the functions of MuSK and the molecular pathogenesis of generalized MG caused by the MuSK autoaintibodies.Next we could produce the MuSK autoantibodies by immunization of MuSK proteins in rabbits in which a MG-like muscular weakness had been induced. We then found clear-cut evidence that these MuSK antibodies specifically inhibited the AChR clustering response to all known stimuli including those of the agrin-independent pathways. Agrin induces AChR clustering by activation of MuSK, whereas agrin-independent stimuli did not. That is, the MuSK autoantibodies rigorously inhibited AChR clustering mediated by multiple pathways, an outcome that broadens general comprehension of MG's pathogenesis(submitted for publication in 2004).Finally, we prepared a large amount of MuSK protein for the analysis of protein structure. We are now screening the optimal conditions for the crystallization to analyze the structure using a synchrotron(Spring-8) in Harima-riken. In addition, we are now analyzing MuSK-lacZ-knock-in mice to elucidate the MuSK functions in the organisms.