Catabolic regulation of the expression of the major myelin glycoprotein by Schwann cells in culture

K. R. Brunden, Anthony John Windebank, J. F. Poduslo

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Previous studies have suggested that neonatal Schwann cell cultures deprived of axonal contact do not express components of the myelin membrane, including the mayor myelin glycoprotein P0. In contrast, Schwann cells from permanently transected, adult nerve exhibit continued biosynthesis of P0 after culture, suggesting that the ability to express the myelin glycoprotein may depend on the degree of cellular differentiation. To examine further the ability of Schwann cell cultures to express P0 as a function of age, we have performed precursor incorporation studies on endoneurial explants from 4- to 12-day-old rat sciatic nerves after 5 days in culture. The data reveal that explants from 12-day-old animals synthesize detectable levels of this integral myelin protein when assayed by [3H]mannose incorporation, even though there is no apparent myelin assembly in the cultures. Pulse-chase analysis of cultures from 12-day-old rats demonstrates that [3H]mannose-labeled P0 is substantially degraded within 3 h. This catabolism largely can be prevented by the addition of swainsonine, ammonium chloride, or L-methionine methyl ester to the pulse-chase media. The former agent alters oligosaccharide processing whereas the latter two compounds inhibit lysosomal function. The P0 synthesized by the 12-day explant cultures following the addition of swainsonine is readily fucosylated, implying that the protein has progressed at least as far as the medial Golgi before its exit and subsequent catabolism. If cultures from 4-, 6-, and 8-day-old animals are analyzed for P0 biosynthesis by [3H]mannose incorporation in the presence of swainsonine, detectable levels of the glycoprotein are seen. The inability to demonstrate the presence of P0 in earlier studies of neonatal cultures were presumably due in part to the rapid lysosomal catabolism of the protein after translation.

Original languageEnglish (US)
Pages (from-to)459-466
Number of pages8
JournalJournal of Neurochemistry
Volume54
Issue number2
DOIs
StatePublished - 1990

Fingerprint

Swainsonine
Schwann Cells
Mannose
Myelin Sheath
Cell culture
Glycoproteins
Cell Culture Techniques
Biosynthesis
Cells
Rats
Animals
Myelin P0 Protein
Myelin Proteins
Ammonium Chloride
Oligosaccharides
Protein Biosynthesis
Proteins
Sciatic Nerve
Membranes
Processing

Keywords

  • [H]mannose
  • Catabolic regulation
  • Cellular differentiation
  • Major myelin glycoprotein
  • Schwann cells
  • Sciatic nerves

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

Cite this

Catabolic regulation of the expression of the major myelin glycoprotein by Schwann cells in culture. / Brunden, K. R.; Windebank, Anthony John; Poduslo, J. F.

In: Journal of Neurochemistry, Vol. 54, No. 2, 1990, p. 459-466.

Research output: Contribution to journalArticle

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abstract = "Previous studies have suggested that neonatal Schwann cell cultures deprived of axonal contact do not express components of the myelin membrane, including the mayor myelin glycoprotein P0. In contrast, Schwann cells from permanently transected, adult nerve exhibit continued biosynthesis of P0 after culture, suggesting that the ability to express the myelin glycoprotein may depend on the degree of cellular differentiation. To examine further the ability of Schwann cell cultures to express P0 as a function of age, we have performed precursor incorporation studies on endoneurial explants from 4- to 12-day-old rat sciatic nerves after 5 days in culture. The data reveal that explants from 12-day-old animals synthesize detectable levels of this integral myelin protein when assayed by [3H]mannose incorporation, even though there is no apparent myelin assembly in the cultures. Pulse-chase analysis of cultures from 12-day-old rats demonstrates that [3H]mannose-labeled P0 is substantially degraded within 3 h. This catabolism largely can be prevented by the addition of swainsonine, ammonium chloride, or L-methionine methyl ester to the pulse-chase media. The former agent alters oligosaccharide processing whereas the latter two compounds inhibit lysosomal function. The P0 synthesized by the 12-day explant cultures following the addition of swainsonine is readily fucosylated, implying that the protein has progressed at least as far as the medial Golgi before its exit and subsequent catabolism. If cultures from 4-, 6-, and 8-day-old animals are analyzed for P0 biosynthesis by [3H]mannose incorporation in the presence of swainsonine, detectable levels of the glycoprotein are seen. The inability to demonstrate the presence of P0 in earlier studies of neonatal cultures were presumably due in part to the rapid lysosomal catabolism of the protein after translation.",
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