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Transient overexpression of alpha-Synuclein in OLN-93 oligodendroglial cells is not cytotoxic and not affected by HSP70

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Alpha-Synuclein (alpha-syn) accumulates in neurons and glia in a number of neurodegenerative disorders. The cytotoxicity and solubility of alpha-syn can be modified by the molecular chaperone HSP70. In multiple system atrophy (MSA), alpha-syn-positive glial cytoplasmic inclusions (GCIs) originating in oligodendrocytes are specifically prominent. Alpha-Synuclein is not detectable in mature oligodendrocytes in the normal brain, but we have shown previously that it is present in cultured rat brain oligodendrocytes [1] and down-regulated as the cultures mature. Hence, GCI formation might be causally related to a specific upregulation of the protein during pathological situations.

To test if alpha-syn at a high level is cytotoxic to oligodendroglial cells and that HSP70 modifies its properties, we have transiently transfected OLN-93 cells, a cell line with oligodendroglia characteristics, and also OLN-93 cells permanently expressing HSP70 (OLN-HSP70), with plasmids encoding alpha-syn. The data show that alpha-syn does not cause cell death, but leads to a disorganisation of the microtubule network to a similar extent in both cell lines. Furthermore, HSP70 did not improve the solubility of alpha-syn, as investigated by determining the amount of alpha-syn in the detergent insoluble fraction. When cells were treated with oxidative stress, exerted by hydrogen peroxide, alpha-syn overexpressing cells did not reveal an altered or enhanced sensitivity to the stress situation as compared to control OLN-93 cells. Also, alpha-syn did not protect cells from oxidative stress, which has been suggested before, since it shares similarities with small heat shock proteins. However, OLN-HSP70 cells showed a higher resistance to oxidative stress, both in the presence and absence of alpha-syn. After treatment with hydrogen peroxide thioflavine S-positive staining, indicating fibrillary protein deposits, was not observable. Thioflavine S staining was only detectable, when cells were treated with hydrogen peroxide first and then with the proteasomal inhibitor MG-132. This was seen independently of the presence of HSP70. Thus, in the present cell system, alpha-syn overexpression is not cytotoxic, and HSP70 is not the major player in altering the properties of alpha-syn.

References

  1. 1.

    Richter-Landsberg C, Gorath M, Trojanowski JQ, Lee VM: alpha-synuclein is developmentally expressed in cultured rat brain oligodendrocytes. J Neurosci Res. 2000, 62: 9-14. 10.1002/1097-4547(20001001)62:1<9::AID-JNR2>3.0.CO;2-U.

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Correspondence to Petra Scholz.

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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (https://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Keywords

  • Multiple System Atrophy
  • Proteasomal Inhibitor
  • Cytoplasmic Inclusion
  • Small Heat Shock Protein
  • Microtubule Network