CSIG-30. FUNCTIONAL CHARACTERISATION OF A NOVEL MUTATION IN PRKCA, THE MAJOR DRIVER OF CHORDOID GLIOMAS

Abstract

Abstract Chordoid gliomas (ChG) are a rare low-grade brain tumour, believed to be derived from Tanycytes. An analysis by the team previously identified a novel mutation present in all ChGs: PRKCA p.D463H. This mutation involves a D463H amino acid substitution at the kinase domain of the Protein kinase C alpha (PKCα) and represents the hallmark of ChG. PKCα is a serine/threonine kinase, that carries out the regulation of various functions in the cell. The aim of the project is to identify novel and biologically relevant PKCα D463H signalling pathways, which will demonstrate the involvement and the role of this mutated kinase in cellular functions implicated in the development of ChGs. The D463H mutation affects a critical residue of the kinase domain of PKCα, suggesting that such change may modify substrate affinity and specificity. Following the purification of the mutated form of PKCα, we have shown it is an inactive kinase, that has a dominant negative effect over the wild type (WT) PKCα. The mutation affects the tertiary structure of the protein, resulting in a more open, unstable protein. Phosphoproteomic analysis of HEK cells overexpressing the mutant protein has shown a global loss of PKCα substrate phosphosites compared to the WT condition. By understanding these changes, integrated with our snRNAseq and bulk RNAseq data of ChGs, we hope to elucidate the mechanism by which the mutation leads to tumorigenesis. Finally, the candidates will be explored in a representative context, by exploring the PKCɑ D463H mutation in primary rat Tanycyte culture and in vivo model. These models will allow us to study the effect of the mutation on cellular processes involved in the development of this rare tumour.