The Gateway Hypothesis: A new framework for unraveling diverse leukodystrophies

描述（由申请人提供）：以前，没有概念框架将脑白质营养不良中观察到的不同分子和细胞破坏联系到产生作为这些疾病标志的全身性CNS白色物质破坏的连贯模型中。缺乏连贯的模型对于星形胶质细胞中的分子破坏尤其成问题，星形胶质细胞与成为sclerosis的少突胶质细胞髓鞘相距甚远。我们最近提出了“网关假说”来解释这些疾病的特征是中枢神经系统髓鞘的广泛破坏。我们提出，广泛性髓鞘硬化症是由突变或免疫破坏的蛋白质组成的主要运输途径K+和水内和细胞之间的panglial合胞体。我们和其他人已经确定了K+和水运输途径的蛋白质，当突变或破坏时，破坏离子稳态，主要是因为K+和水继续进入panglial合胞体，但在它们可以退出之前被阻止。网关假说表明，药物，减少K+进入潘格利亚合胞体可能会提供新的治疗方法来治疗这些疾病。该途径的两个丰富的蛋白质分子-KV 1（有髓鞘轴突的电压门控通道）和Cx 29（一种不形成间隙连接的少突胶质细胞连接蛋白）-被认为是水和K+进入panglial合胞体的“门户”。因此，这些紧密相关的蛋白质，以及电压门控钠通道在节点的郎维尔，提出作为潜在的目标，在许多脑白质营养不良的药物干预。其基本原理是通过减少轴突Na+内流和/或K+外流及其耦合的内流到周围髓鞘中，可以充分降低引起髓鞘肿胀和硬化的渗透负荷，以允许未受损的K+和水转运途径重新分配药理学降低的渗透负荷，从而允许正常的细胞修复机制部分恢复髓鞘功能，允许长期治疗，可能包括神经胶质干细胞替代疗法。我们建议用途：1）超微结构和超分辨率光学显微镜免疫细胞化学; 2）分子下拉测定; 3）细胞培养物中Cx 29和KV 1通道的表达，通过细胞内记录电生理学进行监测;和4）记录正常和运动野生型和Cx 29敲除小鼠的小鼠胼胝体急性切片中的少突胶质细胞。因此，我们将在轴突质膜和Cx 29通道在相邻的最内层的髓鞘和特征的KV 1通道，并建立这些分子的功能相互作用的K+“网关”进入panglial合胞体。有了这些新的数据，网关假说将提供一个框架，用于确定哪些脑白质营养不良立即适合药物干预和/或干细胞治疗，允许医疗资源提供给可以最有效治疗的患者。

DESCRIPTION (provided by applicant): Previously, there was no conceptual framework for linking the diverse molecular and cellular disruptions seen in the leukodystrophies into a coherent model for the production of the generalized CNS white matter destruction that is the hallmark of these diseases. This lack of a coherent model was particularly problematic for molecular disruptions in astrocytes, which are far removed from the oligodendrocyte myelin that becomes sclerotic. We recently introduced the "Gateway Hypothesis" to account for the widespread destruction of CNS myelin that characterizes these diseases. We proposed that generalized myelin sclerosis is caused by mutation or immunological disruption of proteins comprising the primary transport pathways for K+ and water within and between cells of the panglial syncytium. We and others had identified proteins of the K+ and water transport pathway that, when mutated or destroyed, disrupt ionic homeostasis, primarily because K+ and water continue to enter the panglial syncytium but are blocked before they can exit. The Gateway Hypothesis suggests that pharmacological agents that reduce K+ entry into the panglial syncytium may provide new therapeutic approach to treating these diseases. Two abundant protein molecules of that pathway - KV1 (the voltage-gated channels of myelinated axons) and Cx29 (a poorly-understood oligodendrocyte connexin that does not form gap junctions) - are proposed to represent the "gateway" for entry of water and K+ into the panglial syncytium. As such, these tightly-associated proteins, as well as voltage-gated sodium channels at nodes of Ranvier, are proposed as potential targets for pharmacologic intervention in many of the leukodystrophies. The rationale is that by reducing axonal Na+ influx and/or K+ efflux and its coupled influx into the surrounding myelin, the osmotic burden that causes myelin swelling and sclerosis can be reduced sufficiently to allow undamaged K+ and water transport pathways to redistribute the pharmacologically-reduced osmotic load, thereby permitting normal cellular repair mechanisms to partially restore myelin function, allowing for longer-term treatments, potentially including glial stem cell replacement therapies. We propose to use: 1) ultrastructural and super-resolution light microscopic immunocytochemistry; 2) molecular pull-down assays; 3) expression of Cx29 and KV1 channels in cell culture, with monitoring by intracellular recording electrophysiology; and 4) recording from oligodendrocytes in acute slices of mouse corpus callosum of normal and exercised wildtype and Cx29 knockout mice. We will thus characterize KV1 channels in axon plasma membranes and Cx29 channels in the adjacent innermost layer of myelin and establish functional interaction of those molecules as the K+ "gateway" into the panglial syncytium. With these new data, the Gateway Hypothesis will provide the framework for identifying which of the leukodystrophies are immediately amenable to pharmacologic intervention and/or stem cell therapies, allowing medical resources to be delivered to the patients who can be most effectively treated.