Grabs D, Bergmann M, Schuster T, Fox P A, Brich M, Gratz M
Institut für Anatomie (Charité), Humboldt-Universität Berlin, Germany.
Eur J Neurosci. 1994 Nov 1;6(11):1765-71. doi: 10.1111/j.1460-9568.1994.tb00569.x.
The closely related synaptic vesicle membrane proteins synaptophysin and synaptoporin are abundant in the hippocampal formation of the adult rat. But the prenatal hippocampal formation contains only synaptophysin, which is first detected at embryonic day 17 (E17) in perikarya and axons of the pyramidal neurons. At E21 synaptophysin immunoreactivity extends into the apical dendrites of these cells and in newly formed terminals contacting these dendrites. The transient presence of synaptophysin in axons and dendrites suggests a functional involvement of synaptophysin in fibre outgrowth of developing pyramidal neurons. Synaptoporin expression parallels the formation of dentate granule cell synaptic contacts with pyramidal neurons: the amount of hippocampal synaptoporin, determined in immunoblots and by synaptoporin immunostaining of developing mossy fibre terminals; increases during the first postnatal week. Moreover, in the adult, synaptoporin is found exclusively in the mossy fibre terminals present in the hilar region of the dentate gyrus and the regio inferior of the cornu ammonis. In contrast, synaptophysin is present in all synaptic fields of the hippocampal formation, including the mossy fibre terminals, where it colocalizes with synaptoporin in the same boutons. Our data indicate that granule neuron terminals differ from all other terminals of the hippocampal formation by the presence of both synaptoporin and synaptophysin. This difference, observed in the earliest synaptic contacts in the postnatal hippocampus and persisting into adult life, suggests distinct functions of synaptoporin in these nerve terminals.
紧密相关的突触囊泡膜蛋白突触素和突触孔蛋白在成年大鼠的海马结构中含量丰富。但产前海马结构仅含有突触素，在胚胎第17天（E17）首次在锥体神经元的胞体和轴突中检测到。在E21时，突触素免疫反应性延伸到这些细胞的顶端树突以及与这些树突接触的新形成的终末中。突触素在轴突和树突中的短暂存在表明其在发育中的锥体神经元纤维生长中发挥功能作用。突触孔蛋白的表达与齿状颗粒细胞与锥体神经元突触接触的形成平行：通过免疫印迹法和对发育中的苔藓纤维终末进行突触孔蛋白免疫染色确定的海马突触孔蛋白量，在出生后第一周增加。此外，在成体中，突触孔蛋白仅存在于齿状回门区和海马角下部的苔藓纤维终末中。相反，突触素存在于海马结构的所有突触区域，包括苔藓纤维终末，在那里它与突触孔蛋白共定位在相同的突触小体中。我们的数据表明，颗粒神经元终末与海马结构的所有其他终末不同，因为同时存在突触孔蛋白和突触素。这种差异在出生后海马最早的突触接触中就已观察到，并持续到成年期，提示突触孔蛋白在这些神经终末中具有独特的功能。
