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J. Cell Biol.,
Volume 139, Number 4, November 17, 1997 851-864

* Department of Pharmacology, New York University Medical Center, New York 10016; We have investigated the expression patterns
and subcellular localization in nervous tissue of glypican, a major glycosylphosphatidylinositol-anchored heparan sulfate proteoglycan that is predominantly
synthesized by neurons, and of biglycan, a small, leucine-rich chondroitin sulfate proteoglycan. By laser
scanning confocal microscopy of rat central nervous tissue and C6 glioma cells, we found that a significant portion of the glypican and biglycan immunoreactivity colocalized with nuclear staining by propidium iodide
and was also seen in isolated nuclei. In certain regions,
staining was selective, insofar as glypican and biglycan
immunoreactivity in the nucleus was seen predominantly in a subpopulation of large spinal cord neurons.
The amino acid sequences of both proteoglycans contain potential nuclear localization signals, and these
were demonstrated to be functional based on their ability to target
Shriners Hospital for Crippled
Children, McGill University, Montreal, Canada; and § Department of Pharmacology, State University of New York, Health
Science Center, Brooklyn, New York 11203
-galactosidase fusion proteins to the nuclei of transfected 293 cells. Nuclear localization of
glypican
-galactosidase or Fc fusion proteins in transfected 293 cells and C6 glioma cells was greatly reduced
or abolished after mutation of the basic amino acids or
deletion of the sequence containing the nuclear localization signal, and no nuclear staining was seen in the
case of heparan sulfate and chondroitin sulfate proteoglycans that do not possess a nuclear localization
signal, such as syndecan-3 or decorin (which is closely
related in structure to biglycan). Transfection of COS-1
cells with an epitope-tagged glypican cDNA demonstrated transport of the full-length proteoglycan to the
nucleus, and there are also dynamic changes in the pattern of glypican immunoreactivity in the nucleus of C6
cells both during cell division and correlated with different phases of the cell cycle. Our data therefore suggest that in certain cells and central nervous system regions, glypican and biglycan may be involved in the
regulation of cell division and survival by directly participating in nuclear processes.
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