OGA
Protein O-GlcNAcase (EC 3.2.1.169) (OGA) (Beta-N-acetylglucosaminidase) (Beta-N-acetylhexosaminidase) (Beta-hexosaminidase) (Meningioma-expressed antigen 5) (N-acetyl-beta-D-glucosaminidase) (N-acetyl-beta-glucosaminidase) (Nuclear cytoplasmic O-GlcNAcase and acetyltransferase) (NCOAT) [HEXC] [KIAA0679] [MEA5] [MGEA5]
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Amyotrophic lateral sclerosis (ALS), the most common motor neuron disease, usually occurs in middle-aged people. However, the molecular basis of age-related cumulative stress in ALS pathogenesis remains elusive. Here, we found that mice deficient in NPGPx (GPx7), an oxidative stress sensor, develop ALS-like phenotypes, including paralysis, muscle denervation, and motor neurons loss. Unlike normal spinal motor neurons that exhibit elevated O-GlcNAcylation against age-dependent oxidative stress, NPGPx-deficient spinal motor neurons fail to boost O-GlcNAcylation and exacerbate ROS accumulation, leading to cell death. Mechanistically, stress-activated NPGPx inhibits O-GlcNAcase (OGA) through disulfide bonding to fine-tune global O-GlcNAcylation. Pharmacological inhibition of OGA rescues spinal motor neuron loss in aged NPGPx-deficient mice. Furthermore, expression of NPGPx in ALS patients is significantly lower than in unaffected adults. These results suggest that NPGPx modulates O-GlcNAcylation by inhibiting OGA to cope with age-dependent oxidative stress and protect motor neurons from degeneration, providing a potential therapeutic axis for ALS.
MeSH Terms
- Aging
- Amyotrophic Lateral Sclerosis
- Animals
- Female
- Humans
- Mice
- Mice, Mutant Strains
- Motor Neurons
- Muscle Denervation
- Oxidative Stress
- Paralysis
- beta-N-Acetylhexosaminidases
Keywords
- ALS
- NPGPx
- O-GlcNAcylation
- OGA
- aging
- motor neuron
- oxidative stress
Retina is particularly susceptible to aging as oxidative damage accumulates within retina, leading to age-related retinal dysfunction or even visual loss. However, the underlying mechanisms still remain obscure and effective therapeutic strategy is urgently in need. Here, we quested for the answer particularly focusing on mitochondrial homeostasis and O-GlcNAcylation in rat retina. By comparing expression of electron transfer chain complexes and key factors in mitochondrial biogenesis and dynamics in retinas of aged and young Sprague-Dawley rats, we found that mitochondrial Complex I, II, IV and V were increased in aged retina with decreased mtTFA and Mfn2. Also, we noticed that p38 and JNK of MAPK signaling were substantially more activated in aged retina, suggesting stress induction. In addition, we found that pan-O-GlcNAcylation was remarkably stronger with lower OGA expression in aged retina. To further elucidate the roles of Mfn2 and O-GlcNAcylation, we employed ARPE-19 cells and found that ATP production, oxygen consumption, and mitochondrial membrane potential were reduced and ROS level was increased by Mfn2 knockdown, while treating with PUGNAc or UDP-GlcNAc heightened oxygen consumption and reduced ROS. Our results suggest disrupted mitochondrial homeostasis may increase oxidative stress; yet enhanced O-GlcNAcylation might defend against oxidative stress and promote mitochondrial respiration in aged retina.
MeSH Terms
- Aging
- Animals
- Cell Line
- Gene Knockdown Techniques
- Glycosylation
- Homeostasis
- Humans
- MAP Kinase Signaling System
- Male
- Mitochondria
- Mitochondrial Proteins
- Oxidative Stress
- Oxygen Consumption
- Rats, Sprague-Dawley
- Reactive Oxygen Species
- Retina
- Retinal Pigment Epithelium
- beta-N-Acetylhexosaminidases
Protein glycosylation via O-linked N-acetylglucosaminylation (O-GlcNAcylation) is an important post-translational regulatory mechanism mediated by O-GlcNAc transferase (OGT) and responsive to nutrients and stress. OGT attaches an O-GlcNAc moiety to proteins, while O-GlcNAcase (OGA) catalyzes O-GlcNAc removal. In skeletal muscle of experimental animals, prolonged increase in O-GlcNAcylation associates with age and muscle atrophy. Here we examined the effects of hormone replacement therapy (HRT) and power training (PT) on muscle OGT and OGA gene expression in postmenopausal women generally prone to age-related muscle weakness. In addition, the associations of OGT and OGA gene expressions with muscle phenotype were analyzed. Twenty-seven 50-57-year-old women participated in a yearlong randomized placebo-controlled trial: HRT (n=10), PT (n=8) and control (n=9). OGT and OGA mRNA levels were measured from muscle samples obtained at baseline and after one year. Knee extensor muscle cross-sectional area (CSA), knee extension force, running speed and vertical jumping height were measured. During the yearlong intervention, HRT suppressed the aging-associated upregulation of OGT mRNA that occurred in the controls. The effects of PT were similar but weaker. HRT also tended to increase the OGA mRNA level compared to the controls. The change in the ratio of OGT to OGA gene expressions correlated negatively with the change in muscle CSA. Our results suggest that OGT and OGA gene expressions are associated with muscle size during the critical postmenopausal period. HRT and PT influence muscle OGT and OGA gene expression, which may be one of the mechanisms by which HRT and PT prevent aging-related loss of muscle mass.
MeSH Terms
- Age Factors
- Estrogen Replacement Therapy
- Female
- Finland
- Gene Expression Regulation, Enzymologic
- Glycosylation
- Humans
- Middle Aged
- Muscle Contraction
- Muscle Strength
- Muscle, Skeletal
- N-Acetylglucosaminyltransferases
- Phenotype
- Plyometric Exercise
- Postmenopause
- Protein Processing, Post-Translational
- RNA, Messenger
- Time Factors
- Treatment Outcome
- beta-N-Acetylhexosaminidases
Keywords
- Aging
- CO
- CSA
- Estrogen
- GAPDH
- HRT
- Muscle atrophy
- Muscle cross-sectional area
- O-GlcNAc
- O-GlcNAc transferase
- O-GlcNAcase
- O-linked N-acetylglucosamine
- OGA
- OGT
- PI3K
- PT
- Plyometric power training
- Postmenopausal hormone replacement therapy
- control
- cross-sectional area
- glyceraldehyde 3-phosphate dehydrogenase
- hormone replacement therapy
- phosphatidylinositol-3-kinase
- power training