Elucidating the effect of O-GlcNAc modification on protein stability

The glycosylation of proteins with O-GlcNAc is a ubiquitous post-translational modification found throughout the metazoans. Deregulation of O-GlcNAcylation is implicated in several human diseases including type II diabetes, Alzheimer’s disease, and cancer.

 

However, the basic biochemical roles of O-GlcNAcylation remain largely unanswered. Several recent studies have demonstrated a clear link between O-GlcNAc and cellular thermotolerance.

 

It is likely that a basic function of the O-GlcNAc modification prevents the unfolding or aggregation of target proteins. Dr. King will investigate its role in protein stability through series of biochemical and biophysical experiments to probe the effect of O-GlcNAc on protein unfolding, folding, and aggregation. The results of this research will provide important insights into the basic molecular mechanisms governing O-GlcNAc deregulation in human disease.

 

End of Award Update: July 2022

 

Most exciting outputs

The modification of proteins by O-linked N-acetylglucosamine (O-GlcNAc) is a widespread post-translational modification (PTM) that is dysregulated in several human diseases including type II diabetes, Alzheimer’s disease and cancer. However, research progress in this area is hampered by the fact that it is challenging to detect O-GlcNAc on proteins. Further, the basic biochemical roles of O-GlcNAcylation remain largely unanswered.

 

Therefore, we developed a mass spectrometry based method to precisely map sites of O-GlcNAc on proteins. This method employs a UV laser to produce a diversity of O-GlcNAc retained fragment ions, enabling mapping protein modification sites with unprecedented precision.

 

We then explored the role of O-GlcNAc as a biochemical regulator of protein stability. We developed a new high-throughput approach to profile the effect of O-GlcNAc on the thermostability of the proteome. Using this method, we identify several proteins that are regulated by O-GlcNAc. Interestingly, the majority of these proteins display an O-GlcNAc dependent decrease in stability, challenging the prevailing view of O-GlcNAc as being a predominantly stabilizing modification. Thus, we show that O-GlcNAc is a bi-directional regulator of protein stability. We deliver a powerful approach that provides a blueprint for determining the impact of, in principle, any PTM on the thermostability of thousands of proteins in parallel.

 

Impacts so far
This work delivers powerful tools for exploring the role of O-GlcNAc and other labile PTMs as regulators of protein biochemistry.

 

Potential future influence
Decreased levels of protein O-GlcNAcylation is associated with Alzheimer’s disease. However, the basic biochemical mechanisms underlying this association remain unknown. Here we show that O-GlcNAc regulates the stability of several proteins within human cells, a phenomenon that may impact cellular protein levels in Alzheimer’s disease. This fundamental research is important for understanding the impact O-GlcNAc has on protein structure and stability, particularly in the context of its dysregulation in neurodegenerative disorders.

 

Next steps
We plan to continue exploring the influence O-GlcNAc has on protein structure and function. In doing so, we hope to improve our understanding of the fundamental mechanisms underlying neurodegeneration. This research may ultimately provide knowledge that contributes toward the development of new therapeutic strategies.

 

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