MICA: Role of D1R-D3R heteromers on striatal function in L-DOPA-induced dyskinesias

许多帕金森氏症患者对使用最广泛的药物左旋多巴（L-DOPA）治疗效果不佳，他们会出现无法控制的身体运动，使他们感到羞耻，甚至摔倒受伤。我们和其他医生认为，这是因为一种叫做多巴胺受体的蛋白质在神经细胞中与一种叫做异构体的不寻常结构联系在一起。然而，没有人知道异构体是如何以及在哪里形成的，它们是否会影响其他受体，以及它是否真的会让人感觉不好。我们已经证明，患有实验性帕金森氏症的动物在接受人类治疗后，大脑中确实有更多的异构体。现在，我们想用特殊的动物来观察异构体是在哪里形成的。此外，我们还与一些公司进行了接触，以制造我们设计的更小的蛋白质，这些蛋白质可以分解异构体，然后用于防止药物的副作用。大脑中对帕金森病的表现至关重要的一部分被称为纹状体。它是由脉冲流入控制的，这些脉冲释放出一种叫做多巴胺的物质。帕金森氏症的主要问题是多巴胺的来源丢失。在治疗中，左旋多巴用来弥补多巴胺的缺乏。重要的是，纹状体中并不是所有的神经细胞都是一样的：有两种不同性质的亚型，特别是它们对多巴胺的反应。神经细胞通过一种叫做突触的结构来交流和传递信息。传递信息的神经细胞（突触前）通过释放化学递质来传递信息。接收细胞（突触后）通过存在于其体内的特殊受体蛋白或称为树突的细延伸来检测信号。在接触点，树突具有芽状突起，称为树突棘，具有处理信号所需的分子机制。纹状体中不同类型的多巴胺受体对多巴胺的反应不同，以特定的方式传递信号。通常它们是分开的，但也可以聚集成异聚体，以不同的方式传输信号。脊髓中其他特殊的受体蛋白包括AMPA和NMDA受体，它们负责大脑中几乎所有神经元之间的快速通信。关于AMPA， NMDA和多巴胺受体之间的相互作用，无论是在健康还是帕金森病中，我们都知道很多。例如，我们知道很多方式，它们如何影响彼此的工作或强或弱，或者来自一个受体的信号如何使其他受体融入突触或完全离开突触，从而调节突触的整体功能。然而，当多巴胺受体异构体存在时，同样的规则是否适用，或者它们在帕金森病中可能产生的后果，我们几乎一无所知。这很重要，因为它可以告诉我们为什么病人的大脑会做出错误的计算并发出错误的信号，从而导致不必要的运动。为了回答所有这些问题，我们将使用特殊的动物，让我们能够区分纹状体中的神经细胞亚型，甚至让我们看到异构体何时存在，因为它们会发出荧光。我们将在这些动物身上施用导致帕金森病的化学物质。然后，使用特殊的方法，我们将能够追踪荧光多巴胺受体异构体，并在活细胞中观察它们。为了实现这一目标，我们将使用强大的共聚焦显微镜来观察神经细胞内的微小细节。我们善于运用这种方法，所以我们可以尽量减少动物的数量。了解异源异构体的作用以及它们自身是如何被调节的，将有助于我们试图找到防止它们超越纹状体控制的方法。这将帮助我们设计出一种对抗帕金森病及其治疗的有害副作用的新策略。

Many people with Parkinson's disease do not respond well to therapy with the most widely-used drug called L-DOPA, having uncontrollable body movements that make them feel ashamed or even fall and get injured. We and other doctors think that this occurs because proteins called dopamine receptors associate in unusual structures called heteromers in nerve cells. However, no one knows how and where heteromers are formed, whether they affect other receptors and if it actually makes people feel bad. We have shown that there really are many more heteromers in brains of the animals with experimental Parkinson's disease put on human therapy. Now, we want to use special animals that will enable us to see where heteromers are formed. Further, we made contacts with companies to make smaller proteins of our design that will break heteromers apart, which could then be used to prevent side effects of drugs. A part of the brain that is essential for manifestations of Parkinson's disease is called striatum. It is controlled by inflow of impulses that release a substance called dopamine. The main problem of Parkinson's disease is that the source of dopamine is lost. In therapy, L-DOPA serves to compensate for the lack of dopamine.Importantly, not all nerve cells in striatum are the same: there are two subtypes with contrasting properties, particularly how they react to dopamine. Nerve cells communicate and transmit information across structures called synapses. The sending nerve cell (presynaptic) relays the information by releasing chemical transmitters. The receiving cell (postsynaptic) detects that signal by specialized receptor proteins present on its body or fine extensions called dendrites. At the points of contact, dendrites have bud-like protrusions called dendritic spines that possess molecular machinery necessary to process the signal. Different types of dopamine receptors in striatal spines respond to dopamine differently, transmitting the signal in a specific way. Normally they stand apart, but can also aggregate into heteromers, which will transmit the signal in a different way.Among other specialized receptor proteins in spines are AMPA and NMDA receptors, responsible for nearly all of the fast communication between neurones in the brain.A lot is known about interplay between AMPA, NMDA and dopamine receptors, both in health and Parkinson's disease. For example, we know many ways how they affect each other to work more or less strongly or how the signals from one receptor make other receptors to incorporate into the synapse or completely leave it, thus modulating the overall synaptic function. Almost nothing is, however, known whether the same rules apply when dopamine receptor-heteromers are present, or about the consequences they may have in Parkinson's disease. This is important because it could tell us why patient's brains make wrong calculations and send wrong signals that result in unwanted movements. To answer all these questions, we will use special animals that allow us to tell between subtypes of nerve cells in striatum, even allowing us to see when heteromers are present in them, because they become fluorescent. We will apply chemicals that cause Parkinson's disease-like condition in these animals. Then, using special methods, we will be able to track the fluorescent dopamine receptor heteromers and see them within the living cells. To achieve this, we will use a powerful confocal microscopy to see tiny details within nerve cells. We are good in applying this methodology, so we can minimize the number of animals used. Understanding what heteromers do and how they themselves are regulated will help us try to find the way to prevent them from overtaking control over striatum. This will help us devise a new strategy in fight against Parkinson's disease and the deleterious side effects of its treatment.