Comparative Proteomics Reveals Dysregulated Mitochondrial O‑GlcNAcylation in Diabetic Hearts

O-linked β-N-acetylglucosamine (O-GlcNAc),
a post-translational modification on serine and threonine residues
of many proteins, plays crucial regulatory roles in diverse biological
events. As a nutrient sensor, O-GlcNAc modification (O-GlcNAcylation)
on nuclear and cytoplasmic proteins underlies the pathology of diabetic
complications including cardiomyopathy. However, mitochondrial O-GlcNAcylation,
especially in response to chronic hyperglycemia in diabetes, has been
poorly explored. We performed a comparative O-GlcNAc profiling of
mitochondria from control and streptozotocin (STZ)-induced diabetic
rat hearts by using an improved β-elimination/Michael addition
with isotopic DTT reagents (BEMAD) followed by tandem mass spectrometric
analysis. In total, 86 mitochondrial proteins, involved in diverse
pathways, were O-GlcNAcylated. Among them, many proteins have site-specific
alterations in O-GlcNAcylation in response to diabetes, which suggests
that protein O-GlcNAcylation is a novel layer of regulation mediating
adaptive changes in mitochondrial metabolism during the progression
of diabetic cardiomyopathy.