Patricia Bimboese, Craig J Gibson, Stefan Schmidt, Wanqing Xiang, Barbara E Ehrlich
Journal of Biological Chemistry
The inositol 1,4,5-trisphosphate receptor (InsP(3)R), an intracellular calcium channel, has three isoforms with >65% sequence homology, yet the isoforms differ in their function and regulation by post-translational modifications. We showed previously that InsP(3)R-1 is functionally modified by O-linked Î²-N-acetylglucosamine glycosylation (O-GlcNAcylation) (Rengifo, J., Gibson, C. J., Winkler, E., Collin, T., and Ehrlich, B. E. (2007) J. Neurosci. 27, 13813-13821). We now report the effect of O-GlcNAcylation on InsP(3)R-2 and InsP(3)R-3. Analysis of AR4-2J cells, a rat pancreatoma cell line expressing predominantly InsP(3)R-2, showed no detectable O-GlcNAcylation of InsP(3)R-2 and no significant functional changes despite the presence of the enzymes for addition (O-Î²-N-acetylglucosaminyltransferase) and removal (O-Î²-N-acetylglucosaminidase) of the monosaccharide. In contrast, InsP(3)R-3 in Mz-ChA-1 cells, a human cholangiocarcinoma cell line expressing predominantly InsP(3)R-3, was functionally modified by O-GlcNAcylation. Interestingly, the functional impact of O-GlcNAcylation on the InsP(3)R-3 channel was opposite the effect measured with InsP(3)R-1. Addition of O-GlcNAc by O-Î²-N-acetylglucosaminyltransferase increased InsP(3)R-3 single channel open probability. Incubation of Mz-ChA-1 cells in hyperglycemic medium caused an increase in the InsP(3)-dependent calcium release from the endoplasmic reticulum. The dynamic and inducible nature of O-GlcNAcylation and the InsP(3)R isoform specificity suggest that this form of modification of InsP(3)R and subsequent changes in intracellular calcium transients are important in physiological and pathophysiological processes.
Call us at 1-800-4-BIORAD (1-800-424-6723)
Copyright © 2014 Bio-Rad Laboratories, Inc. All rights reserved.