Hexosamine biosynthetic pathway regulates exosome secretion by promoting O-GlcNAcylation of SNAP25

Exosomes are essential mediators of intercellular communication and play critical roles in tumor progression, immune regulation, and viral infection. However, how exosomes are generated within cells, transported, and ultimately secreted remains incompletely understood.

Recently, the research team led by Prof. Jin Zhong at the Shanghai Institute of Materia Medica, Chinese Academy of Sciences, published new findings revealing that the hexosamine biosynthetic pathway (HBP)—a metabolic branch of glucose metabolism—promotes the O-GlcNAc glycosylation of SNAP25, thereby enhancing the assembly efficiency of the SNARE complex and facilitating the release of exosomes to the extracellular space. This study provides important mechanistic insights into the metabolic basis underlying the elevated exosome secretion frequently observed in tumor cells.

There is a well-known but insufficiently explained observation: tumor cells exhibit not only highly active metabolic states but also an enhanced capacity for exosome secretion. The researchers found that replacing glucose with galactose in cell culture significantly inhibited glycolysis and markedly reduced exosome secretion, which could be also achieved by lowering the glucose concentration or a glycolysis inhibitor 2-DG. This reduction was observed not only in Huh7 hepatoma cells but also in 293T and A549 cells, demonstrating that glucose metabolism exerts a broad regulatory influence on exosome release across multiple cell models. Exosomes secreted by tumour cells have been reported to mediate cell-to-cell communication, reprogram tumour microenviroment and help tumours evade immune system. Interfering metabolic pathway may abrogate those effects mediated by tumour exosomes.

To determine the specific metabolic pathway responsible for this effect, the researchers focused on the hexosamine biosynthetic pathway (HBP), which converts glycolytic intermediates into UDP-GlcNAc, the donor substrate for protein O-GlcNAcylation. Knockdown of the rate-limiting HBP enzyme GFPT1, inhibition of O-GlcNAc transferase (OGT), or depletion of glutamine from the culture medium all reduced global O-GlcNAc levels and led to decreased exosome secretion. Conversely, increasing O-GlcNAcylation partially restored exosome output. These results establish a key role for HBP and O-GlcNAc modification in promoting exosome release.

Further analysis revealed that this regulation does not occur at the early stages of exosome biogenesis. The formation of multivesicular bodies (MVBs) and the number of intraluminal vesicles (ILVs) were not significantly reduced. Instead, MVBs accumulated near the perinuclear region and showed reduced motility, suggesting that the defect likely lies in the transport and membrane fusion steps.

The researchers then screened for specific proteins involved in this regulation and focused on the SNARE complex, a well-established mediator of vesicle–membrane fusion. They discovered that SNAP25, a core SNARE component, displayed elevated O-GlcNAcylation levels in response to increased glucose availability. Enhancing SNAP25 O-GlcNAc modification strengthened its interaction with other SNARE partners, including STX1A and VAMP2, thereby improving SNARE complex assembly and facilitating MVB–plasma membrane fusion, ultimately promoting exosome release.

This study not only explains why tumor cells with high metabolic activity exhibit increased exosome secretion, but also offers a new conceptual framework for understanding metabolic regulation within the tumor microenvironment. In the future, additional key nodes within the HBP–O-GlcNAc regulatory axis may serve as promising intervention targets, offering new strategies to modulate tumor growth and intercellular communication.

About Author:

Dr. Jin Zhong is a Professor at Shanghai Institute of Materia Medica, Chinese Academy of Sciences. He received his Ph.D. degree at the University of Texas at Austin, USA, where he studied microbial mobile elements from 1997 to 2003. He was further trained in molecular virology as a postdoctoral fellow at The Scripps Research Institute, USA from 2003 to 2007. During his postdoctoral training period, he and colleagues developed a robust cell culture model for hepatitis C virus infection. Since 2007 he has been the head of Unit of Viral Hepatitis at Institut Pasteur of Shanghai and later Shanghai Institute of Immunity and Infection, Chinese Academy of Sciences. He has also been Adjunct Professor at ShanghaiTech University since 2013. Dr. Zhong’s major research interest is to study molecular virology, cell biology, and innate immune responses as well as the development of vaccines and antiviral therapeutics for medically important RNA viruses, including hepatitis C virus (HCV), Ebola virus (EBOV), and other emerging pathogenic RNA viruses. He has published over 130 research articles.