Sinha Ashis, Nickerson Gabrielle, Bouyain Samuel, Matthews Russell T
Department of Neuroscience and Physiology, State University of New York Upstate Medical University, Syracuse, New York 13210.
Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, Missouri 64110.
bioRxiv. 2024 Nov 5:2024.11.05.622114. doi: 10.1101/2024.11.05.622114.
Perineuronal nets (PNNs), are neuron-specific substructures within the neural extracellular matrix (ECM). These reticular structures form on a very small subset of neurons in the central nervous system (CNS) and yet have a profound impact in regulating neuronal development and physiology. PNNs are well-established as key regulators of plasticity in the CNS. Their appearance coincides with the developmental transition of the brain more to less plastic state. And, importantly, numerous studies have demonstrated that indeed PNNs play a primary role in regulating this transition. There is, however, a growing literature implicating PNNs in numerous roles in neural physiology beyond their role in regulating developmental plasticity. Accordingly, numerous studies have shown PNNs are altered in a variety of neurological and neuropsychiatric diseases, linking them to these conditions. Despite the growing interest in PNNs, the mechanisms by which they modulate neural functions are poorly understood. We believe the limited mechanistic understanding of PNNs is derived from the fact that there are limited models, tools or techniques that specifically target PNNs in a cell-autonomous manner and without also disrupting the surrounding neural ECM. These limitations are primarily due to our incomplete understanding of PNN composition and structure. In particular, there is little understanding of the neuronal cell surface receptors that nucleate these structures on subset of neurons on which they form in the CNS. Therefore, the main focus our work is to identify the neuronal cell surface proteins critical for PNN formation and structure. In our previous studies we demonstrated PNN components are immobilized on the neuronal surface by two distinct mechanisms, one dependent on the hyaluronan backbone of PNNs and the other mediated by a complex formed by receptor protein tyrosine phosphatase zeta (RPTPζ) and tenascin-R (Tnr). Here we first demonstrate that the Tnr-RPTPζ complex in PNNs is bound to the cell surface by a glycosylphosphatidylinositol (GPI)-linked receptor protein. Using a biochemical and structural approach we demonstrate the GPI-linked protein critical for binding the Tnr-RPTPζ complex in PNNs is contactin-1 (Cntn1). We further show the binding of this complex in PNNs by Cntn1 is critical for PNN structure. We believe identification of CNTN1 as a key cell-surface protein for PNN structure is a very significant step forward in our understanding of PNN formation and structure and will offer new strategies and targets to manipulate PNNs and better understand their function.
神经周网（PNNs）是神经细胞外基质（ECM）内特定于神经元的亚结构。这些网状结构在中枢神经系统（CNS）中极少数神经元上形成，但对调节神经元发育和生理功能具有深远影响。PNNs已被充分确认为中枢神经系统可塑性的关键调节因子。它们的出现与大脑从可塑性较强状态向较弱状态的发育转变相吻合。而且，重要的是，大量研究表明PNNs在调节这种转变中确实起着主要作用。然而，越来越多的文献表明，PNNs在神经生理学中的作用远不止于调节发育可塑性。相应地，大量研究表明PNNs在多种神经和神经精神疾病中发生改变，将它们与这些疾病联系起来。尽管对PNNs的兴趣日益浓厚，但人们对它们调节神经功能的机制却知之甚少。我们认为，对PNNs机制理解有限的原因在于，目前专门以细胞自主方式靶向PNNs且不破坏周围神经ECM的模型、工具或技术有限。这些限制主要是由于我们对PNN组成和结构的理解不完整。特别是，对于在中枢神经系统中形成PNNs的神经元子集上使这些结构成核的神经元细胞表面受体了解甚少。因此，我们工作的主要重点是确定对PNN形成和结构至关重要的神经元细胞表面蛋白。在我们之前的研究中，我们证明PNN成分通过两种不同机制固定在神经元表面，一种依赖于PNNs的透明质酸主干，另一种由受体蛋白酪氨酸磷酸酶zeta（RPTPζ）和腱生蛋白-R（Tnr）形成的复合物介导。在这里，我们首先证明PNNs中的Tnr-RPTPζ复合物通过糖基磷脂酰肌醇（GPI）连接的受体蛋白与细胞表面结合。使用生化和结构方法，我们证明对结合PNNs中的Tnr-RPTPζ复合物至关重要的GPI连接蛋白是接触蛋白-1（Cntn1）。我们进一步表明Cntn1对该复合物在PNNs中的结合对PNN结构至关重要。我们认为，将CNTN1鉴定为PNN结构的关键细胞表面蛋白是我们在理解PNN形成和结构方面向前迈出的非常重要的一步，将为操纵PNNs并更好地理解其功能提供新的策略和靶点。
