Down-regulation of hydrogen peroxide-induced PKCδ activation in N-acetylglucosaminyltransferase III-transfected HeLaS3 cells

N-acetylglucosaminyltransferase III (GnT-III) is a key enzyme that inhibits the extension of N-glycans by introducing a bisecting N-acetylglucosamine residue. Our previous studies have shown that modification of N-glycans by GnT-III affects a number of intracellular signaling pathways, In this study, the effects of GnT-III on the cellular response to reactive oxygen species (ROS) were examined. We found that an overexpression of GnT-III suppresses H2O2-induced apoptosis in HeLaS3 cells. In the case of GnT-III transfectants, activation of Jun N-terminal kinase (JNK) following H2O2 treatment was markedly reduced compared with control cells. Either the depletion of protein kinase C (PKC) by prolonged treatment with phorbol 12-myristate 13-acetate or the inhibition of PKC by the specific inhibitor 117 attenuated the H2O2-induced activation of JNK1 and apoptosis in control cells but not in the GnT-III transfectants. Furthermore, we found that H2O2-induced phosphorylation of PKCdelta was markedly suppressed in GnT-III transfectants. Rottlerin, a specific inhibitor of PKCdelta, significantly inhibited H2O2-induced activation of JNK1 in control cells, indicating that PKCdelta is involved in the pathway. These findings suggest that the overexpression of GnT-III suppresses H2O2-induced activation of PKCdelta-JNK1 pathway, resulting in inhibition of apoptosis.