Inhibition of phospholamban phosphorylation by O-GlcNAcylation: implications for diabetic cardiomyopathy
Open Access
- 18 May 2010
- journal article
- research article
- Published by Oxford University Press (OUP) in Glycobiology
- Vol. 20 (10), 1217-1226
- https://doi.org/10.1093/glycob/cwq071
Abstract
Cardiac-type sarco(endo)plasmic reticulum Ca2-ATPase (SERCA2a) plays a major role in cardiac muscle contractility. Phospholamban (PLN) regulates the function of SERCA2a via its Ser16-phosphorylation. Since it has been proposed that the Ser/Thr residues on cytoplasmic and nuclear proteins are modified by O-linked N-acetylglucosamine (O-GlcNAc), we examined the effect of O-GlcNAcylation on PLN function in rat adult cardiomyocytes. Studies using enzymatic labeling and co-immunoprecipitation of wild type and a series of mutants of PLN showed that PLN was O-GlcNAcylated and Ser16 of PLN might be the site for O-GlcNAcylation. In cardiomyocytes treated with O-(2-acetamido-2-deoxy-d-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc), the O-GlcNAcylation was significantly increased compared to non-treated cells. Simultaneously, Ser16-phosphorylation of PLN was reduced. In Chinese hamster ovary cells where PLN cDNA and O-GlcNAc transferase siRNA were co-transfected, the Ser16-phosphorylation of PLN was significantly increased compared to controls. The same results were observed in heart homogenates from diabetic rats. In a co-immunoprecipitation of PLN with SERCA2a, the physical interaction between the two proteins was increased in PUGNAc-treated cardiomyocytes. Unlike non-treated cells, the activity of SERCA2a and the profiles of calcium transients in PUGNAc-treated cardiomyocytes were not significantly changed even after treatment with catecholamine. These data suggest that PLN is O-GlcNAcylated to induce the inhibition of its phosphorylation, which correlates to the deterioration of cardiac function. This might define a novel mechanism by which PLN regulation of SERCA2a is altered under conditions where O-GlcNAcylation is increased, such as those occurring in diabetes.Keywords
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