Inhibition of phospholipase C-β1-mediated signaling by O-GlcNAc modification

Here we report inhibition of phospholipase C-β1 (PLC-β1)-mediated signaling by post-translational glycosylation with β-N-acetylglucosamine (O-GlcNAc modification). In C2C12 myoblasts, isoform-specific knock-down experiments using siRNA showed that activation of bradykinin (BK) receptor led to stimulation of PLC-β1 and subsequent intracellular Ca²⁺ mobilization. In C2C12 myotubes, O-GlcNAc modification of PLC-β1 was markedly enhanced in response to treatment with glucosamine (GlcNH₂), an inhibitor of O-GlcNAase (PUGNAc) and hyperglycemia. This was associated with more than 50% inhibition of intracellular production of IP₃ and Ca²⁺ mobilization in response to BK. Since the abundance of PLC-β1 remained unchanged, these data suggest that O-GlcNAc modification of PLC-β1 led to inhibition of its activity. Moreover, glucose uptake stimulated by BK was significantly blunted by treatment with PUGNAc. These data support the notion that O-GlcNAc modification negatively modulates the activity of PLC-β1.