RAPIDLY LABELLING AND EXPORTED NEURONAL PROTEIN; [3H]FUCOSE AS A PRECURSOR, AND EFFECTS OF CYCLOHEXIMIDE AND COLCHICINE

Abstract

Abstract— The characteristics of a rapidly labelled and rapidly transported neuronal perikaryal protein fraction (Rose & Sinha. 1974a) were investigated in three experiments. (1) The kinetics of labelling of neuronal cell body and neuropil fractions from [3H]fucose were followed and shown to be similar to those from [3H]lysine, the label first appearing in the neuronal fraction and then being exported. The neuronal/neuropil incorporation ratio fell from 1.37 at 1 h to 0.77 at 4 h. (2) When cycloheximide (5 mg/kg) was injected intraperitoneally 15 min after [3H]lysine, incorporation into neuronal protein was inhibited to a greater extent (85%) than into neuropil (60%). (3) Colchicine was injected at a dose (40 μg/kg) sufficient to prevent accumulation of radioactively labelled protein into synaptosomes but insufficient to affect total incorporation of precursor into protein. [3H]Lysine was injected 1 h after colchicine and neurons and neuropil fractions made 1 h and 4 h later; colchicine inhibited the export of labelled protein from the neuronal perikaryon and its accumulation in the neuropil. We conclude that the rapidly labelled neuronal protein is partially glycoprotein in character and may be normally transported from the cell body by way of the axonal/(dendritic?) flow mechanism.