A Catalytically Inactive Protein Kinase C alpha Mutation Drives Chordoid Glioma by Pathway Rewiring

Area of Science:

• Neuro-oncology
• Molecular Biology
• Genetics

Background:

• Chordoid glioma (ChG) is a rare, low-grade brain tumor.
• A recurrent D463H mutation in protein kinase C alpha (PKCα) is a hallmark of ChG.
• This mutation's functional impact beyond simple inactivation is not well understood.

Purpose of the Study:

• To investigate the molecular mechanisms by which the PKCα _D463H mutation contributes to chordoid glioma.
• To elucidate the interactome and functional consequences of the mutant PKCα in ChG.

Main Methods:

• In vitro and in cellulo activity assays to assess PKCα _D463H catalytic activity.
• Phosphoproteomic and proximity labeling mass spectrometry to identify protein interactions and phosphorylation changes.
• Co-immunoprecipitation mass spectrometry to confirm protein binding partners.
• Single nuclei RNA sequencing (snRNAseq) to determine the cell of origin for ChG.

Main Results:

• PKCα _D463H is catalytically inactive but acts as a dominant-negative mutant, suppressing endogenous PKC activity.
• Overexpression of PKCα _D463H alters substrate phosphorylation and leads to binding with proteins involved in cell-cell junctions.
• snRNAseq data indicate that ChG originates from specialized tanycytes.

Conclusions:

• The D463H mutation in PKCα promotes neomorphic non-catalytic scaffolding, distinct from its enzymatic function.
• This altered scaffolding impairs cell junction function, contributing to chordoid glioma pathogenesis.
• The findings identify tanycytes as the cell of origin for chordoid glioma.