Journal of Neuroscience, Vol 4, 1875-1883, Copyright © 1984 by Society for Neuroscience
Characterization of glycolipids synthesized in an identified neuron of Aplysia californica
AA Sherbany, RT Ambron and JH Schwartz
Because radioactive precursors can be injected directly into the cell body
or axon of R2, a giant, identified neuron of the Aplysia abdominal
ganglion, it was possible to show that glycolipid is synthesized in the
cell body, inserted into membranes along with glycoprotein, and then
exported into the axon within organelles that are moved by fast axonal
transport. After intrasomatic injection of N-[3H]-acetyl-D- galactosamine,
five major 3H-glycolipids were identified using thin layer polysilicic acid
glass fiber chromatography. At least two of the lipids are negatively
charged. Analysis of 32P-labeled lipid from the abdominal ganglion revealed
the presence of 2-aminoethylphosphonate, indicating that these polar
substances are sphingophosphonoglycolipids. The major 3H-glycolipids
synthesized in R2 are similar to a family of phospholipids isolated from
the skin of A. kurodai, previously characterized by Araki et al. (Araki,
S., Y. Komai, and M. Satake (1980) Biochem J. 87: 503-510). Since sialic
acid is absent in Aplysia as in other invertebrates, these polar
glycolipids may function like gangliosides in vertebrates. The polar
3H-glycolipids are synthesized and incorporated into intracytoplasmic
membranes solely in the cell body. Direct injection of the labeled sugar
into the axon revealed no local synthesis or exchange of glycolipid.
Moreover, there was no indication for transfer from glial cells into
axoplasm. Although the incorporation of N-[3H]-acetyl-D-galactosamine into
glycolipid is not affected by anisomycin, an effective inhibitor of protein
synthesis, the export into the axon of membranes containing the newly
synthesized lipid is completely blocked by the drug.(ABSTRACT TRUNCATED AT
250 WORDS)