Summary: Scientists have identified a molecular mechanism linking depression to abnormal sugar modifications on brain proteins. Chronic stress reduces sialylation—a stabilizing sugar modification—within the prefrontal cortex, weakening neural circuit stability and producing depressive symptoms.
By manipulating the enzyme St3gal1, researchers demonstrated its central role: lowering St3gal1 produced depressive-like behaviors in mice, while restoring its levels improved those symptoms. This discovery points beyond traditional neurotransmitter-focused approaches and suggests new diagnostic markers and treatment targets for treatment-resistant depression.
Key Facts:
- New pathway: Depression is associated with disrupted glycosylation on brain proteins, not solely with neurotransmitter imbalances.
- Critical enzyme: Reduced St3gal1 destabilizes neural circuits and can directly induce depressive behaviors.
- Therapeutic potential: The findings highlight glycosylation and sialylation as promising targets for diagnostics and novel treatments.
Source: Institute for Basic Science
Depression is a serious disorder that interferes with daily life through fatigue, sleep disturbances, social withdrawal and an elevated risk of suicide.
The global prevalence of depression has continued to rise, affecting more than 280 million people worldwide as of 2025.
Researchers at the Institute for Basic Science (IBS), led by C. Justin Lee and Boyoung Lee, have described a new pathological mechanism linking altered protein glycosylation in the brain to depressive behaviors.
Their study shows that chronic stress disrupts O-glycan modifications—sugar chains attached to proteins—within the prefrontal cortex (PFC). This disruption specifically affects sialylation, the addition of sialic acid to the ends of glycan chains, a modification that normally stabilizes proteins and synaptic interactions.
Published in Science Advances, the study shifts attention from classic neurotransmitter models of depression toward posttranslational protein changes that alter circuit function. Most current antidepressants target neurotransmitter systems such as serotonin, but roughly half of patients do not achieve adequate relief and many experience side effects. Identifying alternative molecular pathways is critical for developing new therapeutic options.
Glycosylation is a widespread biochemical process that modifies protein structure and function by adding sugar chains. While glycosylation has been extensively studied in cancer, infection and neurodegeneration, its role in mood disorders has been less explored due to technical challenges. The IBS team leveraged high-performance mass spectrometry to map region-specific O-glycosylation across nine brain regions in healthy mice and in mice exposed to chronic stress.
Their analyses revealed distinct glycosylation signatures across brain regions and identified marked alterations in the PFC of stressed animals. The most notable change was reduced sialylation accompanied by lower expression of the sialyltransferase St3gal1, an enzyme responsible for adding sialic acid residues to O-glycans.
To test causality, the researchers manipulated St3gal1 expression in the medial prefrontal cortex (mPFC). Knocking down St3gal1 in nonstressed mice produced depressive-like behaviors—reduced motivation and increased anxiety—even without exposure to chronic stress. Conversely, boosting St3gal1 expression in stressed mice alleviated depressive symptoms. These experiments identify loss of St3gal1 as a molecular driver of depression-like behavior and suggest that enhancing its activity confers resilience to stress.
Further protein-level studies and electrophysiological recordings showed that reduced St3gal1 altered O-glycan structures on synaptic proteins, including neurexin 2 (NRXN2), a synaptic adhesion molecule. These glycan changes impaired inhibitory neuron function, disrupting the balance of excitation and inhibition in local circuits. In effect, small alterations in sugar chains undermined synaptic connectivity and circuit stability, collapsing the networks that regulate emotion.
“This study demonstrates that abnormal glycosylation in the brain is directly connected to the onset of depression,” said Research Fellow Boyoung Lee. “It offers a solid starting point for identifying new diagnostic markers and therapeutic targets beyond neurotransmitters.”
“Depression imposes a major social burden, yet current treatments remain limited,” added Director C. Justin Lee. “These findings could inform therapies not only for depression but also for related psychiatric conditions such as PTSD and schizophrenia, broadening potential treatment strategies.”
Key Questions Answered:
A: They identified disrupted sugar modifications (O-glycans), especially reduced sialylation of proteins in the prefrontal cortex, as a direct contributor to depressive behaviors.
A: The prefrontal cortex, a central region for emotion regulation and decision-making, showed the most significant changes.
A: It highlights glycosylation and the enzyme St3gal1 as novel therapeutic targets beyond traditional neurotransmitter-based approaches, potentially guiding new diagnostics and treatments for treatment-resistant cases.
About this depression research news
Author: William Suh
Source: Institute for Basic Science
Contact: William Suh, Institute for Basic Science
Image: The image is credited to Neuroscience News
Original Research: Open access. “Abnormal O-Glycan Sialylation in the mPFC Contributes to Depressive-like Behaviors in Male Mice” by C. Justin Lee et al., Science Advances
Abstract
Abnormal O-Glycan Sialylation in the mPFC Contributes to Depressive-like Behaviors in Male Mice
Understanding depression’s biological basis and developing more effective treatments remain urgent challenges. Posttranslational modifications, including glycosylation, offer important insights into disease mechanisms but have been difficult to analyze comprehensively.
This study shows that chronic stress produces region-specific alterations in O-glycosylation across the brain, with particularly pronounced changes in the prefrontal cortex. These changes involve reduced sialylation mediated by the sialyltransferase St3gal1. Functionally, reducing St3gal1 in nonstressed mice induced depressive-like behaviors, while overexpressing it in stressed mice rescued those behaviors, indicating a key role for St3gal1 in stress resilience.
The work also identifies candidate glycoprotein targets and downstream regulators of St3gal1, including neurexin 2 (NRXN2) in the medial PFC, linking altered O-glycosylation to synaptic dysfunction and depressive-like outcomes.