Toews A D, Armstrong R, Ray R, Gould R M, Morell P
Department of Biochemistry and Nutrition, University of North Carolina, Chapel Hill 27514.
J Neurosci. 1988 Feb;8(2):593-601. doi: 10.1523/JNEUROSCI.08-02-00593.1988.
Radioactive glycerol, ethanolamine, or choline injected into the vicinity of the cell bodies of rat sciatic nerve sensory fibers is incorporated into phospholipid. Some newly synthesized ethanolamine and choline phosphoglycerides are subsequently committed to transport down the sciatic nerve axons at a rate of several hundred millimeters per day. Most labeled choline phosphoglycerides move uniformly down the axons; in contrast, the crest of moving ethanolamine phosphoglycerides is continually attenuated. These data, as well as differences in the clearance of these phospholipids distal to a nerve ligature, suggest that various classes of labeled phospholipids are differentially unloaded from the transport vector (possibly by exchange with unlabeled lipid in stationary axonal structures) during movement down the axons. The extent of unloading appears to be defined by the base moiety; both diacyl and plasmalogen species of ethanolamine phosphoglycerides exchange extensively with stationary axonal lipids, while most choline phosphoglycerides continue down the axons. Autoradiographic studies with 3H-choline and 3H-ethanolamine demonstrated that most unloaded phospholipid is initially deposited in axonal structures; some of this unloaded lipid is subsequently transferred to the axon/myelin interface (axolemma?) and then to myelin. Although transported ethanolamine phosphoglycerides exchange more extensively with lipids in stationary axonal structures than do choline phosphoglycerides, at early times more label from 3H-choline is found in myelin. A model to resolve this seeming discrepancy is proposed, wherein a differential topographic localization of phospholipid classes in the membrane of the transport vector allows for a preferential extensive exchange of transported ethanolamine phosphoglycerides with lipids in stationary axonal structures, while choline phosphoglycerides become available for rapid transfer to myelin by a process involving vesicle fusion with axolemma.
将放射性甘油、乙醇胺或胆碱注射到大鼠坐骨神经感觉纤维细胞体附近后，它们会被整合到磷脂中。一些新合成的乙醇胺和胆碱磷酸甘油酯随后会以每天数百毫米的速度沿着坐骨神经轴突运输。大多数标记的胆碱磷酸甘油酯在轴突中均匀移动；相比之下，移动的乙醇胺磷酸甘油酯的波峰不断减弱。这些数据，以及神经结扎远端这些磷脂清除率的差异，表明在沿着轴突移动的过程中，不同类别的标记磷脂从运输载体上的卸载方式存在差异（可能是通过与静止轴突结构中的未标记脂质交换）。卸载的程度似乎由碱基部分决定；乙醇胺磷酸甘油酯的二酰基和缩醛磷脂种类都与静止的轴突脂质广泛交换，而大多数胆碱磷酸甘油酯则继续沿着轴突移动。用³H-胆碱和³H-乙醇胺进行的放射自显影研究表明，大多数卸载的磷脂最初沉积在轴突结构中；其中一些卸载的脂质随后转移到轴突/髓鞘界面（轴膜？），然后再转移到髓鞘。尽管运输的乙醇胺磷酸甘油酯比胆碱磷酸甘油酯与静止轴突结构中的脂质交换更广泛，但在早期，髓鞘中³H-胆碱的标记更多。本文提出了一个模型来解释这种明显的差异，即在运输载体膜中磷脂类别的差异地形定位允许运输的乙醇胺磷酸甘油酯与静止轴突结构中的脂质优先进行广泛交换，而胆碱磷酸甘油酯则通过涉及囊泡与轴膜融合的过程快速转移到髓鞘中。
