Dipartimento di Fisiologia Generale e Ambientale, Universitá di Napoli, Naples, Italy; Istituto di Biologia Cellulare, Universitá di Perugia, Perugia, Italy; Istituto Internazionale di Genetica e Biofisica, Naples, Italy; Electron Microscopy Section, University of Ulm, Ulm, Germany; and Department of Psychiatry, Western Psychiatric Institute and Clinic, University of Pittsburgh, Pittsburgh, 15213 Pennsylvania.
Mol Cell Neurosci. 1993 Aug;4(4):366-74. doi: 10.1006/mcne.1993.1046.
A synaptosomal fraction from squid brain containing a large proportion of well-presarved nerve terminals displays a high rate of [(35)S]methionine incorporation into protein. The reaction is dependent on time and protein concentration, is strongly inhibited by hypo-osmotic shock and cycloheximide, and is not affected by RNase. Chloramphenicol, an inhibitor of mitochondrial protein synthesis, partially inhibits the reaction. The ionic composition of the incubation medium markedly modulates the rate of [(35)S]methionine incorporation. Na(+) and K(+) ions are required for maximal activity, while complete inhibition is achieved by addition of the calcium ionophore A23187 and, to a substantial extent, by tetraethylammonium, ouabain, and high concentrations K(+). A thermostable inhibitor of synaptosomal protein synthesis is also present in the soluble fraction of squid brain. Using sucrose density gradient sedimentation procedures, cytoplasmic polysomes associated with nascent radiolabeled peptide chains have been identified in the synaptosomal preparation. Newly synthesized synaptosomal proteins are largely associated with a readily sedimented particulate fraction and may be resolved by gel electrophoresis into more than 30 discrete bands ranging in size from about 14 to 200 kDa. The electrophoretic pattern of the newly synthesized synaptosomal proteins is significantly different from the corresponding patterns displayed by the giant axon's axoplasm and by glial and nerve cell bodies (in the stellate nerve and ganglion, respectively). On the whole, these observations suggest that the nerve endings from squid brain are capable of protein synthesis.
从鱿鱼脑中分离出的突触小体部分含有大量保存完好的神经末梢，显示出很高的[(35)S]甲硫氨酸掺入蛋白质的速率。该反应依赖于时间和蛋白质浓度，强烈抑制低渗休克和环己酰亚胺，并不受 RNase 影响。氯霉素，一种线粒体蛋白质合成的抑制剂，部分抑制反应。孵育介质的离子组成显著调节[(35)S]甲硫氨酸掺入的速率。Na(+)和 K(+)离子是最大活性所必需的，而钙离子载体 A23187 的加入和四乙铵、哇巴因和高浓度 K(+)的加入则完全抑制了反应。鱿鱼脑中可溶性部分也存在一种热稳定的突触小体蛋白质合成抑制剂。使用蔗糖密度梯度沉淀程序，在突触小体制剂中鉴定出与新生放射性标记肽链相关的细胞质多核糖体。新合成的突触小体蛋白主要与易于沉淀的颗粒部分相关，并可通过凝胶电泳解析为大小从约 14 到 200 kDa 的 30 多个离散带。新合成的突触小体蛋白的电泳图谱与巨大轴突轴浆和神经胶质细胞和神经元体（分别在星状神经和神经节中）显示的相应图谱明显不同。总的来说，这些观察结果表明鱿鱼脑中的神经末梢具有蛋白质合成能力。
