Role of prion protein in the dynamic of multiprotein signaling modules related to stemness of glioblastoma stem cells: its functional role and potential therapeutic target

Abstract

Glioblastoma (GBM), the most aggressive and frequent form of brain malignant tumors in adults, contains a subpopulation of tumor cells, called GBM stem cells (GSC), essential for tumor maintenance, metastasis and resistance to therapy. GSC plasma membrane markers functionally relevant present potential as a therapeutic target for the treatment of this aggressive disease. Our group has shown that the GPI-anchored membrane glycoprotein, prion protein (PrPC) is enriched in GSC and is co-expressed with conventional GSC markers, such as CD133. The loss-of-function of PrPC in GSC results in inhibition of self-renewal, proliferation, and capacity for tumor formation. Several ligands have been described for PrPC, including some extracellular and transmembrane matrix functionally relevant to the biology of GSC. CD133, CD44 and integrins ±6 and ±7, major GSC markers, are able to interact and/or share with PrPC the same membrane microdomain, being preferentially located in lipid rafts. It has been proposed that PrPC acts as a scaffold protein on the cell surface, recruiting and organizing molecules on signaling platforms with different biological consequences. Giving these data, this study aims to investigate the role of PrPC as a key molecule in the maintenance of the undifferentiated state of GSC by modulating signaling platforms associated with stemness and as a target for GBM therapy. For this purpose, PrPC loss-of-function studies will be conducted using the CRISPR/Cas9 technique in GSC. The expression, cell surface distribution and intracellular trafficking of potential molecules components of the signaling module will be addressed by immunophenotyping, biochemical assays, confocal microscopy, and functional assays of self-renewal and proliferation. The participation of PrPC and its partners, members of the signaling platform, will also be evaluated in chemoresistance assays using temozolomide. Thus, we propose to use the scaffold concept for PrPC as an alternative for the development of new strategies for the treatment of glioblastoma, besides to demonstrate that PrPC can act as a key regulator of GSC stemness maintenance. (AU)