Biology subjects

Fei, G. Q.

Publications and source records attributed to Fei, G. Q..

3 recordsLinked to original sources

bioRxiv2026

Lipid Changes due to Low O-GlcNAc and the Downstream Consequences

O-GlcNAc transferase (OGT) is an essential mammalian glycosyltransferase that installs O-GlcNAc onto thousands of cytosolic and nuclear proteins. Dysregulated glycosylation by OGT is associated with disease states, including cancer and neurodegeneration. However, cellular consequences of acute loss of O-GlcNAc remain poorly understood. Here, we employed a cell-permeable small molecule inhibitor of OGT, OSMI-4, coupled with transcriptomic and lipidomic analyses to characterize the effects of O-GlcNAc depletion in human cell lines. Loss of O-GlcNAc led to changes in expression of lipid metabolism genes and remodeling of the lipidome, with unsaturated phosphatidylcholines (PCs), saturated lysophosphatidylcholines (LPCs) and unsaturated storage lipids accumulating. We also observed increased lipid droplets. Our results suggest that polyunsaturated fatty acids (PUFAs) accumulate in the membrane under low O-GlcNAc conditions and that cells buffer this accumulation by removing PUFAs from membrane lipids and sequestering them in lipid droplets. We found that treatment with OSMI-4 sensitizes cells to ferroptosis inducers, likely because accumulated cell membrane PUFAs undergo peroxidation. Taken together, our results highlight lipid remodeling as an important process that mediates the downstream effects of loss of O-GlcNAc. It may be possible to exploit the synergy between OGT inhibitors and ferroptosis inducers for therapeutic benefit.

cell biology↗

bioRxiv2020

Mammalian Cell Proliferation Requires Noncatalytic Functions of O-GlcNAc Transferase

O-GlcNAc transferase (OGT), found in the nucleus and cytoplasm of all mammalian cell types, is essential for cell proliferation. Why OGT is required for cell growth is not known. OGT performs two enzymatic reactions in the same active site. In one, it glycosylates thousands of different proteins, and in the other, it proteolytically cleaves another essential protein involved in gene expression. Deconvoluting OGTs myriad cellular roles has been challenging because genetic deletion is lethal; complementation methods have not been established. Here, we developed approaches to replace endogenous OGT with separation-of-function variants to investigate the importance of OGTs enzymatic activities for cell viability. Using genetic complementation, we found that OGTs glycosyltransferase function is required for cell growth but its protease function is dispensable. We next used complementation to construct a cell line with degron-tagged wild-type OGT. When OGT was degraded to very low levels, cells stopped proliferating but remained viable. Adding back catalytically-inactive OGT rescued growth. Therefore, OGT has an essential noncatalytic role that is necessary for cell proliferation. By developing a method to quantify how OGTs catalytic and noncatalytic activities affect protein abundance, we found that OGTs noncatalytic functions often affect different proteins from its catalytic functions. Proteins involved in oxidative phosphorylation and the actin cytoskeleton were especially impacted by the noncatalytic functions. We conclude that OGT integrates both catalytic and noncatalytic functions to control cell physiology. SignificanceMammalian cells contain only one glycosyltransferase, OGT, that operates in the nucleus and cytoplasm rather than the secretory pathway. OGT is required for cell proliferation, but a basic unanswered question is what OGT functions are essential. This question is challenging to address because OGT has thousands of glycosylation substrates, two different enzymatic activities, and a large number of binding partners. Here, by establishing genetic tools to replace endogenous OGT with variants that preserve only a subset of its activities, we show that only a low level of glycosylation activity is required to maintain cell viability; however, cell proliferation requires noncatalytic OGT function(s). The ability to replace OGT with variants provides a path to identifying its essential substrates and binding partners.

biochemistry↗

bioRxiv2020

O-GlcNAc regulates gene expression by controlling detained intron splicing

Intron detention in precursor RNAs serves to regulate expression of a substantial fraction of genes in eukaryotic genomes. How detained intron (DI) splicing is controlled is poorly understood. Here we show that a ubiquitous post-translational modification called O-GlcNAc, which is thought to integrate signaling pathways as nutrient conditions fluctuate, controls detained intron splicing. Using specific inhibitors of the enzyme that installs O-GlcNAc (O-GlcNAc transferase, or OGT) and the enzyme that removes O-GlcNAc (O-GlcNAcase, or OGA), we first show that O-GlcNAc regulates splicing of the highly conserved detained introns in OGT and OGA to control mRNA abundance in order to buffer O-GlcNAc changes. We show that OGT and OGA represent two distinct paradigms for how DI splicing can control gene expression. We also show that when DI splicing of the O-GlcNAc-cycling genes fails to restore O-GlcNAc homeostasis, there is a global change in detained intron levels. Strikingly, almost all detained introns are spliced more efficiently when O-GlcNAc levels are low, yet other alternative splicing pathways change minimally. Our results demonstrate that O-GlcNAc controls detained intron splicing to tune system-wide gene expression, providing a means to couple nutrient conditions to the cells transcriptional regime.

cell biology↗