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Updated: May 11, 2025
Analysis of SCAP N-glycosylation and Trafficking in Human Cells
Published on: November 8, 2016
Targeting PGM3 abolishes SREBP-1 activation-hexosamine synthesis feedback regulation to effectively suppress brain
Huali Su1,2, Yaogang Zhong1,2, Liqing He3
1Department of Radiation Oncology, Ohio State Comprehensive Cancer Center, Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, and College of Medicine at The Ohio State University, Columbus, OH 43210, USA.
Abstract:
Elevated hexosamine biosynthesis fuels tumor growth by facilitating protein and lipid glycosylation. But which enzyme in this pathway is better to serve as an antitumor target remains unclear. Here, we revealed that targeting GFAT1, the rate-limiting enzyme in hexosamine synthesis, exhibits limited inhibitory effects on glioblastoma (GBM), the most lethal brain tumor. This outcome is due to the compensation of NAGK-mediated hexosamine salvage pathway. Unexpectedly, inhibiting PGM3, which controls the flux of both de novo hexosamine synthesis and salvage pathways, down-regulates the expression of other enzymes in this pathway and suppresses SREBP-1, a critical lipogenic transcription factor, effectively inhibiting GBM growth. Unexpectedly, SREBP-1 transcriptionally up-regulates the expression of hexosamine synthesis enzymes, while inhibition of these enzymes in turn down-regulates SREBP-1 activation via reducing N-glycosylation of its transporter, SCAP. Our study identified PGM3 as a promising target for treating GBM. Its inhibition disrupts the SREBP-1 activation-hexosamine synthesis positive feedback regulation to effectively eliminate GBM cells.
Insights
Targeting the hexosamine synthesis pathway in glioblastoma (GBM) is complex. PGM3 inhibition effectively suppresses GBM growth by disrupting a key feedback loop involving SREBP-1, unlike GFAT1 inhibition.
Area of Science:
- Biochemistry
- Cancer Biology
- Metabolic Pathways
Background:
- Elevated hexosamine biosynthesis supports tumor growth through glycosylation.
- The optimal enzyme target within this pathway for cancer therapy remains undetermined.
- Glioblastoma (GBM) is an aggressive brain tumor with high metabolic demands.
Purpose of the Study:
- To evaluate the efficacy of targeting key enzymes in the hexosamine biosynthesis pathway, specifically GFAT1 and PGM3, as an antitumor strategy for GBM.
- To elucidate the regulatory mechanisms and feedback loops governing hexosamine synthesis and its impact on GBM proliferation.
Main Methods:
- Enzyme inhibition assays targeting GFAT1 and PGM3 in GBM models.
- Analysis of downstream effects on protein and lipid glycosylation.
- Investigation of the role of the hexosamine salvage pathway and SREBP-1 in compensatory mechanisms.
- Assessment of the feedback regulation between SREBP-1 and hexosamine synthesis enzymes.
Main Results:
- Inhibition of GFAT1 showed limited efficacy against GBM due to compensatory activation of the NAGK-mediated hexosamine salvage pathway.
- PGM3 inhibition effectively suppressed GBM growth.
- PGM3 inhibition downregulated other hexosamine synthesis enzymes and suppressed SREBP-1 activity.
- A positive feedback loop was identified where SREBP-1 upregulates hexosamine synthesis enzymes, and enzyme inhibition downregulates SREBP-1 activation via SCAP N-glycosylation.
Conclusions:
- PGM3 is a more effective therapeutic target than GFAT1 for GBM.
- Inhibiting PGM3 disrupts the SREBP-1/hexosamine synthesis feedback loop, leading to GBM cell death.
- Targeting PGM3 offers a promising strategy for novel GBM treatments.
