Abstract
Migration of oligodendrocyte precursors along axons is a necessary prerequisite for myelination, but little is known about underlying mechanisms. NG2 is a large membrane proteoglycan implicated in oligodendrocyte migration. Here we show that a PDZ domain protein termed syntenin-1 interacts with NG2 and that syntenin-1 is necessary for normal rates of migration. The association of syntenin-1 with NG2, identified in a yeast two-hybrid screen, was confirmed by colocalization of both proteins within processes of oligodendroglial precursor cells and by coimmunoprecipitation from cell extracts. Syntenin-1 also colocalizes with NG2 in "co-capping" assays, demonstrating a lateral association of both proteins in live oligodendrocytes. RNA interference-mediated down-regulation of syntenin-1 in glial cells results in a significant reduction of migration in vitro, as does the presence of polyclonal antibody against NG2. Thus syntenin plays a role in the migration of oligodendroglial precursors, and we suggest that NG2-syntenin-1 interactions contribute to this.
Highlights
The NG2 proteoglycan is a type I membrane protein that is expressed by a variety of immature cells of several embryonic tissue origins including glia, muscle progenitor cells, and pericytes [1]
In the central nervous system, expression of NG2 was originally thought to specify oligodendroglial progenitor cells, but more recent data suggest that NG2-expressing cells encompass a wider range of immature glial cells in white and gray matter
Tion assays [5, 6], and NG2 plays a role in cell spreading in melanoma tumors, which express melanoma chondroitin sulfate proteoglycan (MCSP), the human ortholog of NG2 [7]
Summary
Animals—NMRI mice were obtained from the Central Animal Facility of the University of Mainz. The Oli-neu cell line was cultured on poly-L-lysine-coated coverslips in Sato medium containing 1% horse serum according to Trotter and co-workers [13]. Lysates were pre-absorbed with protein A-Sepharose (Amersham Biosciences) for 1 h at 4 °C (preclear) followed by incubation with primary antibodies overnight at 4 °C. Cells were washed three times with blocking buffer and incubated for 30 min with the appropriate Cy2and Cy3-conjugated secondary antibodies (Dianova, Hamburg, Germany) diluted in blocking buffer. Cells were fixed for 5 min with 4% paraformaldehyde, permeabilized with 0.1% Triton X-100 for 5 min, blocked with -mercaptoethanol/10% horse serum, and incubated overnight with pc syntenin-1 antibody. Transformants were grown on synthetic defined media/LeuϪ/ TrpϪ/HisϪ plates; 5 mM 3-amino-1,2,4-triazole was added to the medium to suppress leaky HIS3 reporter gene expression. In this study we have equated the percent increase of marked areas with the migration of the cells
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