The Journal of Neuroscience, March 1, 2001, 21(5):1434-1443
A Ganglioside-Specific Sialyltransferase Localizes to Axons and
Non-Golgi Structures in Neurons
Charlene A.
Stern and
Michael
Tiemeyer
Department of Cell Biology, Yale University School of Medicine, New
Haven, Connecticut 06510
To investigate the tissue distribution and subcellular localization
of ST3GalV (CMP-NeuAc:lactosylceramide
2,3 sialyltransferase/GM3 synthase) in the adult mouse, we generated two antisera against mouse ST3GalV that were designated CS2 (directed against amino acids
K227-I272) and CS14 (directed against amino acids D308-H359). We
previously reported that CS2 antiserum stains medial and
trans-Golgi cisternae in all cell types investigated. In
neural tissue, however, CS14 antiserum reveals a subpopulation of
ST3GalV with a subcellular distribution complementary to CS2 antiserum.
CS14 antiserum strongly stains axons in cortical, cerebellar,
brainstem, and spinal cord tissue sections. The subcellular
localization of neuronal ST3GalV is maintained in primary cultures of
rat hippocampal neurons and in PC12 cells. In PC12 cells, ST3GalV
localization evolves during NGF-induced differentiation such that a
pool of enzyme leaves the Golgi for a distal compartment in conjunction
with neurite outgrowth. In PC12 cells transfected with an
epitope-tagged form of ST3GalV, staining for the epitope tag coincides
with expression of endogenous enzyme. The non-Golgi pool of ST3GalV
does not colocalize with markers for the trans-Golgi
network, endosome, or synaptic vesicles, nor is it detected on the cell
surface. Distinct subpopulations of ST3GalV imply that ganglioside
synthesis can occur outside of the Golgi or, alternatively, that a
portion of the total ST3GalV pool subserves a nonenzymatic function.
Significantly fewer transfected cells were found in PC12 cultures
treated with plasmid encoding ST3GalV than in cultures treated with
control plasmid, indicating that the expression of ST3GalV in
excess of endogenous levels results in either cell death or a decreased
rate of cell division.
Key words:
ganglioside; neurons; PC12 cells; sialyltransferase; axon; glycolipid synthesis
Copyright © 2001 Society for Neuroscience 0270-6474/01/2151434-10$05.00/0