In cardiomyocytes glucose deprivation induced increase in O‐GlcNAc is calcium dependent

Abstract

We have previously reported that in neonatal rat ventricular cardiomyocytes (NRVM) glucose deprivation (GD) induced increased in O-linked-N-acetylglucosamine (O-GlcNAc) levels was associated with decreased O-GlcNAcase (OGA) levels. In Neuro-2a neuroblastoma cells it was showed that the effects of GD on O-GlcNAc levels was mediated in part AMP-activated protein kinase (AMPK). Therefore, the goal of this study was to determine if in NRVM the GD induced increase in O-GlcNAc levels was also AMPK dependent and if so whether it was mediated by upstream activation of calcium/calmodulin-dependent protein kinase (CaMK). The AMPK inhibitor Compound-C attenuated the GD-induced increase in O-GlcNAc levels, but only at 40μM; the CaMKK inhibitor STO 609 did not affect the GD-induced increase in O-GlcNAc, even though it is also reported to inhibit AMPK. However, KN93 a CaMK2 inhibitor significantly attenuated GD-induced increase in O-GlcNAc levels in a dose dependent manner (5–20μM). Lowering extracellular Ca2+ with EGTA or blocking Ca2+ entry with verapamil or SKF96365 also decreased the GD-induced increase in O-GlcNAc. These data demonstrate that GD-induced increase in O-GlcNAc is Ca2+ dependent and mediated at least in part by activation of CaMK2. These results provide new insights into the mechanisms underlying the stress induced increase in protein O-GlcNAcylation. Supported by: NIH HL079364, HL101192.