Frei T, von Bohlen und Halbach F, Wille W, Schachner M
Department of Neurobiology, Swiss Federal Institute of Technology, Hönggerberg, Zürich.
J Cell Biol. 1992 Jul;118(1):177-94. doi: 10.1083/jcb.118.1.177.
The neural cell adhesion molecule (N-CAM) engages in diverse functional roles in neural cell interactions. Its extracellular part consists of five Ig-like domains and two fibronectin type III homologous (type III) repeats. To investigate the functional properties of the different structural domains of the molecule in cell interactions and signal transduction to the cell interior, we have synthesized, in a bacterial expression system, the individual domains and tandem sets of individual domains as protein fragments. These protein fragments were tested for their capacity to influence adhesion and spreading of neuronal cell bodies, promote neurite outgrowth, and influence cellular migration patterns from cerebellar microexplants in vitro. Ig-like domains I and II and the combined type III repeats I-II were most efficient for adhesion of neuronal cell bodies, when coated as substrates. Neurite outgrowth was best on the substrate-coated combined type III repeats I-II, followed by the combined Ig-like domains I-V and Ig-like domain I. Spreading of neuronal cell bodies was best on substrate-coated combined type III repeats I-II, followed by Ig-like domain I and the combined Ig-like domains I-V. The cellular migration pattern from cerebellar microexplant cultures plated on a mixture of laminin and poly-L-lysine was modified by Ig-like domains I, III, and IV, while Ig-like domains II and V and the combined type III repeats I-II did not show significant modifications, when added as soluble fragments. Outgrowth of astrocytic processes from the explant core was influenced only by Ig-like domain I. Metabolism of inositol phosphates was strongly increased by Ig-like domain I and less by the Ig-like domains II, III, IV, and V, and not influenced by the combined type III repeats I-II. Intracellular concentrations of Ca2+ and pH values were increased only by the Ig-like domains I and II. Intracellular levels of cAMP and GMP were not influenced by any protein fragment. These experiments indicate that different domains of N-CAM subserve different functional roles in cell recognition and signal transduction, and are functionally competent without nervous system-derived carbohydrate structures.
神经细胞黏附分子（N-CAM）在神经细胞相互作用中发挥着多种功能作用。其细胞外部分由五个免疫球蛋白样结构域和两个纤连蛋白III型同源重复序列（III型）组成。为了研究该分子不同结构域在细胞相互作用和向细胞内部信号转导中的功能特性，我们在细菌表达系统中合成了各个结构域以及各个结构域的串联组合作为蛋白质片段。测试了这些蛋白质片段影响神经元细胞体黏附与铺展、促进神经突生长以及影响小脑微外植体体外细胞迁移模式的能力。当作为底物包被时，免疫球蛋白样结构域I和II以及组合的III型重复序列I-II对神经元细胞体的黏附最为有效。在包被底物的组合III型重复序列I-II上神经突生长最佳，其次是组合的免疫球蛋白样结构域I-V和免疫球蛋白样结构域I。神经元细胞体在包被底物的组合III型重复序列I-II上铺展最佳，其次是免疫球蛋白样结构域I和组合的免疫球蛋白样结构域I-V。当作为可溶性片段添加时，铺在层粘连蛋白和聚-L-赖氨酸混合物上的小脑微外植体培养物的细胞迁移模式受到免疫球蛋白样结构域I、III和IV的影响，而免疫球蛋白样结构域II和V以及组合的III型重复序列I-II未显示出显著影响。来自外植体核心的星形胶质细胞突起生长仅受免疫球蛋白样结构域I影响。肌醇磷酸的代谢受到免疫球蛋白样结构域I的强烈增强，免疫球蛋白样结构域II、III、IV和V影响较小，且不受组合的III型重复序列I-II影响。细胞内Ca2+浓度和pH值仅由免疫球蛋白样结构域I和II升高。细胞内cAMP和GMP水平不受任何蛋白质片段影响。这些实验表明，N-CAM的不同结构域在细胞识别和信号转导中发挥不同的功能作用，并且在没有神经系统衍生的碳水化合物结构的情况下也具有功能活性。
