Increased O-GlcNAcylation altered metabolic signaling in O-GlcNAcase (OGA) knockout embryonic fibroblasts cells and transgenic mice

Tuesday, October 25, 2011 — Poster Session II
Noon – 2:00 p.m.	Natcher Conference Center	NIDDK	SIG/RNA/CYTOK-6

Authors

• C Keembiyehetty
• M Comly
• D Love
• O Gavrilova
• J Hanover

Abstract

O-GlcNAc addition to serine and/or threonine residues is a dynamic post- translational modification analogous to phosphorylation. This cyclical protein modification is mediated by the enzymes O-GlcNAc Transferase (OGT), and O-GlcNAcase (OGA). O-GlcNAc modification has an impact in many cellular signaling pathways and interferes with phophorylation signaling cascades. Perturbations of O-GlcNAc cycling cause metabolic deregulation leading to Diabetes, Alzheimer's diseases and cancer. In the present study, OGA deleted MEF cells and mice were used to investigate the impact of increased O-GlcNAcylated proteins in metabolic signaling. Western blot assay confirmed elevated O-GlcNAcylated proteins in OGA deleted MEFs and mice indicating absence of OGA activity. About 2% of homozygous OGA knock out mice survived to adults, suggesting severe physiological stress associated with increased O-GlcNAcylation. MEF cells showed increased phosphorylation status of AMPK alpha and GSK3 beta proteins under basal conditions which partially alleviated upon insulin stimulation. Microarray data from OGA deleted MEF cells recorded decreased expression in some metabolic genes such as endothelial lipases, while dominant changes were observed in immune system. Serum and body composition of OGA heterozygous mice showed compensatory changes in glucose and lipid metabolism. Proteasome inactivation by O-GlcNAcylation could also affect the normal metabolic sensitivity of lipid droplets.

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