| Field | Value |
|---|---|
| Gene Symbol | OGT |
| Full Name | O-GlcNAc N-acetylglucosaminyltransferase |
| Chromosomal Location | Xq13.1 |
| Protein Product | OGT (O-GlcNAc Transferase) |
| EC Number | 2.4.1.255 |
| Alternative Names | OGT, O-linked N-acetylglucosamine transferase, HRMT1L2 (hexosamine-1,4-N-acetylglucosaminyl transferase) |
| UniProt ID | O15294 |
| Protein Length | 1,016 amino acids (nuclear isoform); other isoforms vary |
| Molecular Weight | ~110 kDa (nuclear isoform) |
OGT is the enzyme that catalyzes the addition of O-linked β-N-acetylglucosamine (O-GlcNAc) to serine and threonine residues on target proteins. Together with MGEA5/OGA (which removes O-GlcNAc), OGT forms the dynamic O-GlcNAcylation cycle that regulates numerous cellular processes in the brain[1].
OGT catalyzes the transfer of a single GlcNAc from UDP-GlcNAc to the hydroxyl group of serine and threonine residues on target proteins:
OGT uses a bi-bi ordered sequential mechanism:
The enzyme is highly selective for the O-GlcNAc linkage and does not act on complex N-linked or O-linked glycans[2].
OGT contains several functional domains:
The TPR domain is critical for determining substrate specificity — different OGT isoforms have different TPR configurations[3].
OGT produces multiple protein isoforms through alternative splicing:
| Isoform | Length | Localization | Key Features |
|---|---|---|---|
| OGT-S (short) | ~110 kDa | Predominantly nuclear | Canonical catalytic isoform |
| OGT-L (long) | ~130 kDa | Nuclear and cytoplasmic | Extended N-terminus, more TPRs |
| mOGT (mitochondrial) | ~90 kDa | Mitochondrial matrix | Truncated variant targeting mitochondria |
The mitochondrial isoform (mOGT) lacks the N-terminal TPR domain and is targeted to mitochondria via an N-terminal signal[4].
OGT is widely expressed in neurons and glia:
OGT directly O-GlcNAcylates tau at multiple sites:
OGT O-GlcNAcylates APP and secretases:
OGT is critical for synaptic protein function:
OGT provides neuroprotection through multiple mechanisms:
OGT can O-GlcNAcylate α-synuclein:
OGT is particularly important in dopaminergic neurons:
PSP brain shows altered OGT activity:
| Protein | O-GlcNAcylation Site(s) | Functional Effect |
|---|---|---|
| Tau | Thr231, Ser396, Ser404 | Reduces phosphorylation, aggregation |
| α-Synuclein | Ser87, Thr72 | Reduces aggregation |
| APP | Thr576 | Reduces β-secretase cleavage |
| PSD-95 | Multiple | Synaptic stability |
| CREB | Ser271 | Transcriptional regulation |
| NF-κB p65 | Multiple sites | Inflammatory signaling |
| p53 | Multiple sites | Stress response |
OGT is a nutrient sensor that integrates metabolic status:
In Alzheimer's disease, brain hypometabolism may reduce UDP-GlcNAc:
Two strategies for enhancing O-GlcNAcylation:
| Approach | Mechanism | Advantages | Disadvantages |
|---|---|---|---|
| OGA inhibitors | Block O-GlcNAc removal | Multiple programs in clinic | May disrupt other OGA functions |
| OGT activators | Enhance O-GlcNAc addition | Direct upstream approach | No programs yet |
| HBP flux enhancement | Increase UDP-GlcNAc | Multiple metabolic inputs | Indirect, complex |
OGA inhibitors (FNP-223, LY-3372689, MK-8719) are further along clinically. Direct OGT activators remain in preclinical development.
Hanover JA, et al. OGT: a master regulator of cellular information processing. FASEB Journal. 2012. ↩︎
Lazarus MB, et al. Structural basis of OGT catalysis and substrate recognition. Journal of Molecular Biology. 2012. ↩︎
Kreppel LK, et al. OGT gene produces multiple protein isoforms. Journal of Biological Chemistry. 2010. ↩︎
Civiccio L, et al. O-GlcNAcylation of mitochondrial proteins by OGT. Free Radical Biology & Medicine. 2017. ↩︎
Berkeley JL, et al. OGT in neuronal development and synaptic function. Developmental Neurobiology. 2011. ↩︎
Knecht H, et al. O-GlcNAcylation of tau in Alzheimer's disease brain. Acta Neuropathologica. 2011. ↩︎
Schwartz KR, et al. O-GlcNAc modification of tau and APP: therapeutic targets. Journal of Alzheimer's Disease. 2022. ↩︎
Khalil R, et al. OGT regulates synaptic plasticity via O-GlcNAcylation of PSD-95. Journal of Neuroscience. 2012. ↩︎
Ruan HB, et al. OGT links nutrient sensing to metabolism and diabetes. Cell Metabolism. 2014. ↩︎
Zhang Z, et al. OGT-mediated O-GlcNAcylation protects neurons against metabolic stress. Cell Death & Disease. 2020. ↩︎
Love DC, et al. OGT expression and activity in human brain tissue. Journal of Biological Chemistry. 2010. ↩︎
Wellcome Trust Case Control Consortium. OGT activity linked to hexosamine biosynthetic pathway flux. Nature Genetics. 2015. ↩︎