Axonal transport of ethanolamine glycerophospholipids

Abstract

The axonal transport of ethanolamine phosphoglycerides has been investigated in the oculomotor nerve and the ciliary ganglion after injection of [1-3H]ethanolamine into the cerebral aqueduct of chickens. The axonally transported labeled lipids were identified by thin layer chromatography and located in cell structures by light and electron microscope radioautography. The major part of axonally transported labeled lipids consisted of diacyl-GPE (phosphatidyl ethanolamine) and alkenylacyl-GPE (ethanolamine plasmalogen). Changes of radioactivity in diacyl-GPE of the ciliary ganglion and of the oculomotor nerve were concomitant with changes of the label in the caliciform nerve endings and the preganglionic axons. The gradual rise of the specific radioactivity in alkenylacyl-GPE of the oculomotor nerve and more specifically of the myelin fraction was corroborated by a gradual accumulation of the label in the myelin sheath of the preganglionic nerve fibers. These data suggest that axonal transport provides diacyl-GPE to the axolemma and the membranous elements of nerve endings. A part of transported diacyl-GPE could be transferred from axon to myelin. In contrast, axonally transported alkenylacyl-GPE would be preferentially and massively transferred to myelin in which they are deposited according to a cumulative process. The selectivity displayed by the distribution of these molecules could be mediated by the axoplasmic reticulum. A lasting defect of axon-myelin transfer of alkenylacyl-GPE could alter myelin integrity and contribute to a demyelinating process.