Non-canonical glycosyltransferase modulates post-hypoxic cardiac myocyte death and mitochondrial permeability transition.
O-linked beta-N-acetylglucosamine (O-GlcNAc) is a dynamic, inducible, and reversible post-translational modification of nuclear and cytoplasmic proteins on Ser/Thr amino acid residues. In addition to its putative role as a nutrient sensor, we have recently shown pharmacologic elevation of O-GlcNAc levels positively affected myocyte survival during oxidant stress. However, no rigorous assessment of the contribution of O-GlcNAc transferase has been performed, particularly in the post-hypoxic setting. Therefore, we hypothesized that pharmacological or genetic manipulation of O-GlcNAc transferase (OGT), the enzyme that adds O-GlcNAc to proteins, would affect cardiac myocyte survival following hypoxia/reoxygenation (H/R). Adenoviral overexpression of OGT (AdOGT) in cardiac myocytes augmented O-GlcNAc levels and reduced post-hypoxic damage. Conversely, pharmacologic inhibition of OGT significantly attenuated O-GlcNAc levels, exacerbated post-hypoxic cardiac myocyte death, and sensitized myocytes to mitochondrial membrane potential collapse. Both genetic deletion of OGT using a cre-lox approach and translational silencing via RNAi also resulted in significant reductions in OGT protein and O-GlcNAc levels, and, exacerbated post-hypoxic cardiac myocyte death. Inhibition of OGT reduced O-GlcNAc levels on voltage dependent anion channel (VDAC) in isolated mitochondria and sensitized to calcium-induced mitochondrial permeability transition pore (mPTP) formation, indicating that mPTP may be an important target of O-GlcNAc signaling and confirming the aforementioned mitochondrial membrane potential results. These data demonstrate that OGT exerts pro-survival actions during hypoxia-reoxygenation in cardiac myocytes, particularly at the level of mitochondria.
Ngoh
Gladys A
GA
Institute of Molecular Cardiology, University of Louisville School of Medicine, Louisville, KY, USA.
Watson
Lewis J
LJ
Facundo
Heberty T
HT
Dillmann
Wolfgang
W
Jones
Steven P
SP
D000118:Acetylglucosaminidase / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D000860:Hypoxia / Q000378:metabolism*; D007425:Intracellular Membranes / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008928:Mitochondria / Q000378:metabolism* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000201:enzymology* / Q000473:pathology*; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics / Q000502:physiology*; D009336:Necrosis; D010539:Permeability; D051381:Rats; D017207:Rats, Sprague-Dawley
D017351:N-Acetylglucosaminyltransferases; C063057:UDP-N-acetylglucosamine-peptide beta-N-acetylglucosaminyltransferase; D000118:Acetylglucosaminidase