Parkin (PARK2) is one of the largest genes in the human genome encoding for an E3 ubiquitin ligase. Its mutationis the cause of early-onset Parkinson’s disease, but recently it is linked to other pathologies including cancer. Parkin acts as a tumor suppressor. It displays wide neuroprotective activity by promoting the removal of damaged mitochondria via mitophagy and increasing proteasomal degradation of toxic substrates. PARK2 primary transcript undergoes to an extensive alternative splicing, which enhances transcriptomic diversification and protein diversity in tissues and cells. To date, GenBank (Unigene cluster Hs.132954) currently lists 26 human PARK2 transcripts corresponding to 21 different alternative splice variants. These transcripts show different patterns of expression and encode proteins with different functions, molecular weight and isoelectric point. A Previous study identified inactivating somatic mutations and frequent intragenic deletions of PARK2 in human cancers (Veeriah et al., 2010). Furthemore Parkin overexpression reduces glioma cells proliferation and analysis of Parkin pathway activation is predictive for the survival outcome of patients with glioma (Yeo et al., 2012). However, all papers focused on the expression of full length of Parkin. In the present work we analyzed the expression pattern of Parkin isoforms in different grade of Astrocytomas and we investigate their functions in a glioblastoma cell line. Immunoblotting analysis using two specific antibodies reveal that Parkin expression is generally higher in malignant glioblastoma than in less invasive gliomas, indicating a correlation between Parkin expression of some isoforms and tumor malignancy. Serum deprivation or treatment with a proteosome inhibitor MG132 or with carbonyl cyanide 3-chlorophenylhydrazone (CCCP), an uncoupling agent that dissipates the mitochondrial membrane potential glioma cells, increased Parkin expression of 100-55-50 kDa isoforms in glioma cells as compared to controls. These results, consistent with other studies, demonstrated a functional connection between Parkin expression, mitochondrial integrity and endoplasmic reticulum stress (ER) (Bouman et al., 2011). Parkin isoforms expression were also confirmed by confocal microscopy analysis. These results suggest that the characterization of some PARK2 isoforms may be usefull clinically to develop a prognostic tool in patients with brain tumor.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.