Wichmann Carolin, Kuner Thomas
Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, InnerEarLab and Institute for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany.
Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, Heidelberg, Germany.
Physiol Rev. 2022 Jan 1;102(1):269-318. doi: 10.1152/physrev.00039.2020.
Chemical synapses are commonly known as a structurally and functionally highly diverse class of cell-cell contacts specialized to mediate communication between neurons. They represent the smallest "computational" unit of the brain and are typically divided into excitatory and inhibitory as well as modulatory categories. These categories are subdivided into diverse types, each representing a different structure-function repertoire that in turn are thought to endow neuronal networks with distinct computational properties. The diversity of structure and function found among a given category of synapses is referred to as heterogeneity. The main building blocks for this heterogeneity are synaptic vesicles, the active zone, the synaptic cleft, the postsynaptic density, and glial processes associated with the synapse. Each of these five structural modules entails a distinct repertoire of functions, and their combination specifies the range of functional heterogeneity at mammalian excitatory synapses, which are the focus of this review. We describe synapse heterogeneity that is manifested on different levels of complexity ranging from the cellular morphology of the pre- and postsynaptic cells toward the expression of different protein isoforms at individual release sites. We attempt to define the range of structural building blocks that are used to vary the basic functional repertoire of excitatory synaptic contacts and discuss sources and general mechanisms of synapse heterogeneity. Finally, we explore the possible impact of synapse heterogeneity on neuronal network function.
化学突触通常被认为是一类在结构和功能上高度多样的细胞间连接，专门用于介导神经元之间的通讯。它们代表了大脑最小的“计算”单元，通常分为兴奋性、抑制性以及调制性类别。这些类别又细分为不同的类型，每种类型代表着不同的结构-功能组合，进而被认为赋予神经网络不同的计算特性。给定类别突触中发现的结构和功能多样性被称为异质性。这种异质性的主要组成部分是突触小泡、活性区、突触间隙、突触后致密区以及与突触相关的胶质细胞突起。这五个结构模块中的每一个都具有独特的功能组合，它们的组合决定了哺乳动物兴奋性突触功能异质性的范围，而这正是本综述的重点。我们描述了突触异质性，它体现在从突触前和突触后细胞的细胞形态到单个释放位点不同蛋白质异构体表达的不同复杂程度水平上。我们试图定义用于改变兴奋性突触接触基本功能组合的结构组成部分的范围，并讨论突触异质性的来源和一般机制。最后，我们探讨突触异质性对神经网络功能的可能影响。
