DNA damage is significant in endothelial cells (EC), particularly in anticancer chemotherapy. Here, we explored whether and how aphidicolin, a DNA-damaging chemical with a promising anticancer activity, alters NO production in bovine aortic endothelial cells (BAEC). In addition to increasing eNOS-Ser1179 phosphorylation, aphidicolin decreased eNOS-Ser116 phosphorylation with a concomitant increase in NO production in a time-dependent manner. The amino acid sequence around the eNOS-Ser116 residue was identified as the substrate site of the regulatory subunit B56δ of protein phosphatase 2A (PP2A). As expected, okadaic acid, a specific PP2A inhibitor, reversed aphidicolin-induced eNOS-Ser116 dephosphorylation in a dose-dependent manner. Aphidicolin also increased B56δ-Ser566 phosphorylation, although expression of neither the catalytic subunit Cα (PP2A Cα) nor B56δ was altered. Ectopic expression of dominant negative (dn)-B56δ reversed all of the observed effects of aphidicolin with respect to phosphorylation of eNOS-Ser116 and B56δ-Ser566. Lastly, aphidicolin-stimulated NO production was also partially attenuated by ectopic expression of dn-B56δ. Taken together, our results are the first to demonstrate that aphidicolin decreases phosphorylation of eNOS-Ser116 as well as eNOS-Ser1179, at least in part by activating PP2A B56δ, resulting in NO release in BAEC.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation ( 2014R1A1A1002873 and 2015R1A2A2A01003315 ) of the Korea government and a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (grant number: HI12C0066 ).
© 2015 Elsevier Inc.
- Endothelial nitric oxide synthase
- PP2A B56δ subunit
- Protein phosphatase 2A