ABSTRACT
Parkin (PK) is an E3-ligase harboring tumor suppressor properties that has been associated to various cancer types including glioblastoma (GBM). However, PK is also a transcription factor (TF), the contribution of which to GBM etiology remains to be established. Methods: The impact of PK on GBM cells proliferation was analyzed by real-time impedance measurement and flow cytometry. Cyclins A and B proteins, promoter activities and mRNA levels were measured by western blot, luciferase assay and quantitative real-time PCR. Protein-protein and protein-promoter interactions were performed by co-immunoprecipitation and by ChIP approaches. The contribution of endogenous PK to tumor progression in vivo was performed by allografts of GL261 GBM cells in wild-type and PK knockout mice. Results: We show that overexpressed and endogenous PK control GBM cells proliferation by modulating the S and G2/M phases of the cell cycle via the trans-repression of cyclin A and cyclin B genes. We establish that cyclin B is regulated by both E3-ligase and TF PK functions while cyclin A is exclusively regulated by PK TF function. PK invalidation leads to enhanced tumor progression in immunocompetent mice suggesting an impact of PK-dependent tumor environment to tumor development. We show that PK is secreted by neuronal cells and recaptured by tumor cells. Recaptured PK lowered cyclins levels and decreased GBM cells proliferation. Further, PK expression is decreased in human GBM biopsies and its expression is inversely correlated to both cyclins A and B expressions. Conclusion: Our work demonstrates that PK tumor suppressor function contributes to the control of tumor by its cellular environment. It also shows a key role of PK TF function in GBM development via the control of cyclins in vitro and in vivo. It suggests that therapeutic strategies aimed at controlling PK shuttling to the nucleus may prove useful to treat GBM.
Subject(s)
Glioblastoma/therapy , Ubiquitin-Protein Ligases/therapeutic use , Animals , Brain Neoplasms/pathology , Cell Cycle , Cell Line, Tumor , Cell Proliferation/genetics , Cyclin A/drug effects , Cyclin A/metabolism , Cyclin B/drug effects , Cyclin B/metabolism , Cyclins/genetics , Female , Flow Cytometry/methods , Gene Expression/genetics , Gene Expression Regulation, Neoplastic/genetics , Genes, Tumor Suppressor/physiology , Glioblastoma/metabolism , Glioblastoma/pathology , Humans , Male , Mice , Mice, Knockout , MicroRNAs/metabolism , Models, Animal , RNA, MessengerABSTRACT
Genome-wide association study (GWAS) has identified several novel genes associated with the risk of Alzheimer's disease (AD), which is a progressive neurodegenerative disease in elders. However, most of the novel genes have not been validated through replication in separated populations. Among them, the BIN1 gene is involved in endocytosis and intracellular trafficking as well as in the formation of ß amyloid plaques and neurofibrillary tangles, which are the main pathological hallmarks of AD. The IL-6 gene has also been frequently associated with AD; however, consistent results have not been found. IL-6, a cytokine from the immune system, is implicated in the pathogenesis of several degenerative diseases. Similar to BIN1, it is suggested that IL-6 is also involved in the formation of ß amyloid plaques. In this case-control study, we aimed to investigate whether single nucleotide polymorphisms in the BIN1 (rs744373) and IL-6 (rs1800795) genes are associated with AD. Genotype frequencies were evaluated via PCR-RFLP in 82 late-onset AD patients and 159 elderly healthy controls, who were matched by age and gender. In this study, no association was found for either polymorphism, suggesting that these genes are not implicated in the aetiology of AD in all populations.
