TIGAR Maintains Mitotic Spindle Organization and βII-Tubulin Stability in Glioma Stem Cells

Glioblastoma (GBM) is a highly aggressive brain malignancy driven by glioma stem cells (GSCs). TIGAR (TP53-induced glycolysis and apoptosis regulator) is primarily known as a metabolic regulator that supports cell survival. However, its non-metabolic functions in neuro-oncology remain largely unexplored. This study aims to investigate the structural role of TIGAR in maintaining mitotic spindle integrity and its potential interplay with the ubiquitin-proteasome system in GSCs.

The clinical relevance of TIGAR expression was evaluated using GEPIA2, TCGA, CGGA, GTEx, and PDX-based analyses. TIGAR function was investigated in human GSC lines (GSC464 and GSC23) using lentiviral shRNA knockdown. Cell cycle progression and spindle morphology were analyzed with flow cytometry and immunofluorescence. Protein-protein interactions and stability were assessed via immunoprecipitation, cycloheximide chase, ubiquitination assays, NAC rescue testing, and Parkin co-depletion rescue assays. In vivo effects of TIGAR depletion were evaluated using GSC-derived orthotopic xenografts in SCID mice and an HRas-driven, p53-deficient primary glioblastoma mouse model.

TIGAR expression is significantly upregulated in human GBM, correlating with tumor malignancy, stemness features, and poor patient prognosis. Public transcriptomic analysis showed a positive association between TIGAR expression and a GSC-related stemness signature, and double immunofluorescence staining confirmed co-localization of TIGAR with SOX2 or CD133 in two PDX models. TIGAR ablation in GSCs induced G2/M arrest and severe spindle defects, and these effects were validated in an additional GSC line. Mechanistically, TIGAR localizes to the mitotic spindle and physically interacts with βII-tubulin, protecting it from Parkin-mediated polyubiquitination and subsequent proteasomal degradation. NAC failed to rescue βII-tubulin loss after TIGAR knockdown, whereas Parkin co-depletion restored βII-tubulin levels and partially normalized the G2/M fraction. In vivo, TIGAR knockdown inhibited GSC-driven tumor growth, reduced stemness marker expression, and significantly prolonged animal survival.

The study reveals an essential non-metabolic function of TIGAR in GBM. The TIGAR-Parkin-βII-tubulin axis serves as a critical mechanism for maintaining mitotic stability and protecting the GSC cytoskeletal network. These findings highlight TIGAR as a structural stabilizer during mitosis and a promising therapeutic target for glioblastoma, independent of p53 mutational status.