Proteolipid Protein Gene Modulates Viability and Phenotype of Neurons

Overexpression or lack of expression of proteolipid protein (PLP) gene by oligodendrocytes causes axonal pathology. It is unclear whether dysfunction of the PLP gene mediates its effects directly on neurons or indirectly by abnormal formation of myelin sheaths. We performed experiments using cocultu...

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Bibliographic Details
Published in:	The Journal of neuroscience Vol. 22; no. 5; pp. 1772 - 1783
Main Authors:	Boucher, Shayne E. M, Cypher, Maria A, Carlock, Leon R, Skoff, Robert P
Format:	Journal Article
Language:	English
Published:	United States Soc Neuroscience 01-03-2002 Society for Neuroscience
Subjects:	Animals Cell Count Cell Division - drug effects Cell Survival - drug effects Cells, Cultured Coculture Techniques Culture Media, Conditioned - pharmacology Ganglia, Spinal - cytology Ganglia, Spinal - drug effects Ganglia, Spinal - metabolism Gene Expression Genes, Reporter Humans Hydrogen-Ion Concentration Immunohistochemistry Kidney - cytology Kidney - metabolism Myelin Proteolipid Protein - genetics Myelin Proteolipid Protein - metabolism Myelin Proteolipid Protein - pharmacology Nerve Tissue Proteins Neurons - cytology Neurons - drug effects Neurons - metabolism Phenotype Rats Rats, Sprague-Dawley Recombinant Fusion Proteins - genetics Recombinant Fusion Proteins - metabolism Transfection Transgenes
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Summary:	Overexpression or lack of expression of proteolipid protein (PLP) gene by oligodendrocytes causes axonal pathology. It is unclear whether dysfunction of the PLP gene mediates its effects directly on neurons or indirectly by abnormal formation of myelin sheaths. We performed experiments using cocultures and conditioned media (CM) to test the direct effect of PLP gene expression on neurons. Non-glial cell lines were stably transfected with PLP or DM20 (an alternate splice variant of PLP) cDNAs. Immunocytochemistry and enhanced green fluorescent protein expression showed that translated products were synthesized and inserted into the plasma membrane in proper conformation. The number of surviving dorsal root ganglion (DRG) neurons was significantly less than controls when cocultured for 5 d with PLP-expressing cells. The number of degenerating neurons increased in a dose-dependent manner corresponding to increasing numbers of PLP-expressing cells. However, the number of surviving DRG neurons cocultured with DM20-expressing cells was comparable to that of controls, indicating that PLP-specific products contributed to decreased neuron survival. When DRG neurons were cultured with CM from PLP- or DM20-expressing cells, significantly fewer neurons survived with CM of PLP- but not DM20-expressing cells. This suggests that secreted factors from PLP-expressing cells contribute to neuronal death. Increased neuronal death found with PLP-expressing cells cannot be attributed to density-dependent artifacts, because in each experiment the density of different cell lines was similar. This effect of CM may be mediated by a negative pH shift elicited from PLP but not DM20 expression. These results indicate that PLP gene products directly modulate neuron viability.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0270-6474 1529-2401
DOI:	10.1523/jneurosci.22-05-01772.2002