Journal article
Molecular bases of JCV T-antigen-mediated transformation of neuronal progenitors--involvement of the IGF-IR - Survivin signaling axis
Journal of neurovirology, Vol.13, pp.83-83
01 Jan 2007
Abstract
The contribution of insulin-like growth factor I receptor (IGF-IR) in polyomavirus T-antigen-mediated cellular transformation is well documented. In addition, both IGF-IR and JCV T-antigen are suspected to play a role in the transformation of neuronal progenitors from the cerebellar granular layer - a critical step in the development of medulloblastoma. Therefore, we investigated how IGF-IR supports cellular transformation by JCV T-antigen. We have addressed this question by utilizing three-dimensional cultures of neural progenitors (neurospheres) isolated from mouse embryos with targeted disruption of the IGF-IR gene (IGF-IR(-/-), and from age-matching non-transgenic littermates. Our results indicate that neurospheres kept in culture conditions supporting cell proliferation, maintain nestin positive neural progenitors phenotype for several generations. Following differentiation of secondary neurospheres, we have detected three distinct cell populations, which were betaIII tubulin (early neuronal marker), GFAP (astrocytic marker), and GalC (oligodendrocytic marker) positive, independently from the presence or absence of the IGF-IR. Nestin positive neurospheres were subsequently transfected with JCV T-antigen, and tested for cell cycle distribution, and protein levels. Our results demonstrate that: (i) more than 50% of IGF-IR(+/+) neurospheres were positive for JCV T-antigen 48 hours after nucleoporation -mediated gene delivery, while only 7% of IGF-IR(-/-) neurospheres showed the expression of this viral oncoprotein. (ii) In IGF-IR(+/+) neurospheres the expression of JCV T-antigen shifted the cells from G1 towards S-G2M phase of the cell cycle, which significantly increased the rate of cell proliferation. In contrast, vast majority of JCV T-antigen positive IGF-IR(-/-) neuronal progenitors were TUNEL positive, (iii) Western blot analyses demonstrated that anti-apoptotic protein, survivin, which expression has been linked with cell proliferation, was downregulated about 10-fold in IGF-IR(-/-) in comparison to IGF-IR(+/+) neuronal progenitors. Interestingly, JCV T-antigen failed to increase survivin protein level in the absence of IGF-IR. In contrast, (iv) JCV T-antigen expressed in differentiated IGF-IR(+/+) neurospheres elevated expression of survivin to the levels detected during cell proliferation. Our results indicate that one of the mechanisms which could explain necessity of the IGF-IR in JCV T-antigen-mediated cellular transformation is reactivation of survivin, which according to our results requires IGF-IR.
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Details
- Title
- Molecular bases of JCV T-antigen-mediated transformation of neuronal progenitors--involvement of the IGF-IR - Survivin signaling axis
- Creators
- E GualcoT SweetL ValleK Reiss
- Publication Details
- Journal of neurovirology, Vol.13, pp.83-83
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Epidemiology and Biostatistics
- Identifiers
- 991021463682004721