Wolff J R, Liu W L, Böttcher H, Krizbai I, Jóo F, Saftig P, Parducz A
Department of Anatomy, University of Göttingen, Germany.
Neuroscience. 1997 Aug;79(3):887-91. doi: 10.1016/s0306-4522(97)00030-4.
Olfactory receptor neurons undergo a continuous turnover in adult mammals. It is largely unknown how their axons invade the olfactory bulb and induce synaptic re-organization in glomeruli. Here, the cytochemical localization of lysosomal acid phosphatase has been studied in olfactory bulbs of adult rats and mice. The enzyme has been identified by specific substrate, inhibitors and absence in lysosomal acid phosphatase-knockout mice. Lysosomal acid phosphatase is located in primary and secondary lysosomes, which are unevenly distributed in the olfactory nerve layer and among olfactory glomeruli. In consecutive sections of glomeruli, the intensity of lysosomal acid phosphatase immunoreactivity co-varied with that of growth-associated phosphoprotein. Electron microscopically, differential lysosomal acid phosphatase staining in glomeruli corresponded to different proportions of labelled and unlabelled axons. Quantification revealed that lysosomal acid phosphatase labelling was strongest in non-synaptic profiles of terminal axons, while it was weak in or even missing from most synaptic profiles. Hence, growing olfactory axons apparently carry more lysosomal acid phosphatase than those which have established synaptic contacts. Following olfactory deafferentation both lysosomal acid phosphatase activity and growth-associated phosphoprotein-43 are lost from glomeruli, suggesting that both proteins are expressed in olfactory sensory axons during growth, while lysosomal acid phosphatase is apparently not a marker of anterograde terminal degeneration.
在成年哺乳动物中，嗅觉受体神经元会持续更新。它们的轴突如何侵入嗅球并诱导肾小球中的突触重组，目前很大程度上尚不清楚。在此，研究了成年大鼠和小鼠嗅球中溶酶体酸性磷酸酶的细胞化学定位。该酶已通过特异性底物、抑制剂以及在溶酶体酸性磷酸酶基因敲除小鼠中的缺失得以鉴定。溶酶体酸性磷酸酶位于初级和次级溶酶体中，这些溶酶体在嗅神经层和嗅小球之间分布不均。在肾小球的连续切片中，溶酶体酸性磷酸酶免疫反应性的强度与生长相关磷酸蛋白的强度共同变化。电子显微镜观察显示，肾小球中溶酶体酸性磷酸酶的差异染色对应于标记和未标记轴突的不同比例。定量分析表明，溶酶体酸性磷酸酶标记在终末轴突的非突触区域最强，而在大多数突触区域则较弱甚至缺失。因此，正在生长的嗅觉轴突显然比已建立突触联系的轴突携带更多的溶酶体酸性磷酸酶。嗅觉传入神经切断后，肾小球中的溶酶体酸性磷酸酶活性和生长相关磷酸蛋白-43均消失，这表明这两种蛋白质在生长过程中均在嗅觉感觉轴突中表达，而溶酶体酸性磷酸酶显然不是顺行性终末变性的标志物。
