CLOCK promotes proliferation of glioblastoma cells through acetylating PRPS1/2.

Abstract

Purpose: The oncogenic impairment of the circadian clock plays an important role in tumorigenesis. However, it remains unclear whether the activation of epidermal growth factor (EGF) receptor (EGFR), which plays a critical role in glioblastoma (GBM) development, regulates the circadian clock and thereby tumorigenesis.

Methods: This study employed molecular techniques including DNA mutagenesis, qPCR, immunoprecipitation, immunofluorescence, and functional assays. CLOCK and PRPS1/2 mutants were generated by site-directed mutagenesis, and gene silencing was performed using shRNA. Gene expression levels were quantified by qPCR, whereas CLOCK localization was analyzed through immunofluorescence and subcellular fractionation. The effects of EGF on GBM cell proliferation and migration were assessed via functional assays. In GBM specimens, the expression of PRPS1/2, CLOCK pS106, and PRPS1/2 K29ac was evaluated by IHC and correlated with tumor aggressiveness and patient survival.

Results: EGF induced CK2-mediated CLOCK S106 phosphorylation, disrupting CLOCK-BMAL1 heterodimerization and suppressing circadian gene expression. Phosphorylated CLOCK bound Exportin1, leading to its nuclear export. Cytosolic CLOCK acetylated PRPS1/2 at K29, preventing HSC70-mediated degradation and enhancing GBM cell proliferation and migration. In human GBM samples, CLOCK pS106, PRPS1/2 K29ac, and PRPS1/2 levels correlated positively with advanced tumor stage and poor survival.

Conclusion: EGF-activated CK2α phosphorylated CLOCK at S106, disrupting circadian rhythms and inducing CLOCK-dependent PRPS1/2 K29 acetylation to drive GBM progression. Clinically, CLOCK pS106, PRPS1/2 K29ac, and PRPS1/2 overexpression correlated with aggressive tumors and poorer prognosis, identifying an EGFR-CLOCK-PRPS1/2 oncogenic axis.