Investigating the Functional Significance of O-GlcNAc Substrate/Interactor Networks
<p>O-linked β-N-acetylglucosamine glycosylation (O-GlcNAcylation) is a dynamic, inducible post-translational modification (PTM) of thousands of intracellular proteins. There are only two enzymes responsible for O-GlcNAc cycling in higher eukaryotes, O-GlcNAc transferase (OGT) and O-GlcNAcase (...
| Summary: | <p>O-linked β-N-acetylglucosamine glycosylation (O-GlcNAcylation) is a dynamic, inducible post-translational modification (PTM) of thousands of intracellular proteins. There are only two enzymes responsible for O-GlcNAc cycling in higher eukaryotes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), which catalyze addition and removal, respectively. We hypothesized that constructing OGT substrate/interactor networks could serve as a useful foundation for understanding the functions of O-GlcNAcylation. Moreover, this approach might reveal novel insights into how OGT is able to coordinate the specific modification of thousands of proteins in response to individual stimuli.</p>
<p>Here, we first sought to validate interactor-substrate relationships suggested by these networks. Specifically, we found that knockdown (KD) of OGT interacting proteins was sufficient to disrupt O-GlcNAcylation of non-interacting OGT substrates. KD of the OGT interacting protein BAP1 changed the O-GlcNAcylation of several of its interactor proteins, many of which do not themselves interact with OGT. This KD strategy was attempted with other potential adaptor proteins such as WDR5 and CDK9, but KD was unsuccessful. KD of the OGT interacting protein GIT1 lead to intriguing changes in the O-GlcNAcylation of liprin-α1. Both of these proteins are vital for synaptic function in excitatory neurons. This result appears significant to the latter protein’s function as it changes with neuronal activity. The aforementioned two findings suggest that association between OGT and its interactors may allow OGT to engage different sets of substrates in different contexts.</p>
<p>Further, we investigated whether modulating global O-GlcNAcylation can affect peroxisome and lipid droplet biogenesis and function, a potentially novel role for O-GlcNAcylation revealed by our network. Together, these studies demonstrate that our networking approach highlights functional connections between OGT interactors and substrates.</p> |
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