Department of Pharmacology, Yale University, New Haven, Connecticut 06520-8066, USA.
J Biol Chem. 2011 May 6;286(18):15688-97. doi: 10.1074/jbc.M110.206482. Epub 2011 Mar 7.
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 β-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-β-N-acetylglucosaminyltransferase) and removal (O-β-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-β-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.
肌醇 1,4,5-三磷酸受体（InsP3R）是一种细胞内钙离子通道，有三个亚型，它们的序列同源性超过 65%，但在功能和翻译后修饰的调节方面存在差异。我们之前曾表明，InsP3R-1 的功能可通过 O 连接的 β-N-乙酰氨基葡萄糖糖基化（O-GlcNAcylation）进行修饰（Rengifo，J.，Gibson，C. J.，Winkler，E.，Collin，T.，和 Ehrlich，B. E.（2007）J. Neurosci. 27，13813-13821）。我们现在报告 O-GlcNAcylation 对 InsP3R-2 和 InsP3R-3 的影响。对 AR4-2J 细胞（一种主要表达 InsP3R-2 的大鼠胰腺癌细胞系）的分析表明，InsP3R-2 中未检测到可检测到的 O-GlcNAcylation，尽管存在添加（O-β-N-乙酰氨基葡萄糖基转移酶）和去除（O-β-N-乙酰氨基葡萄糖苷酶）单糖的酶，但没有明显的功能变化。相比之下，InsP3R-3 在 Mz-ChA-1 细胞（一种主要表达 InsP3R-3 的人胆管癌细胞系）中被 O-GlcNAcylation 功能修饰。有趣的是，O-GlcNAcylation 对 InsP3R-3 通道的功能影响与用 InsP3R-1 测量的影响相反。O-β-N-乙酰氨基葡萄糖基转移酶添加 O-GlcNAc 增加了 InsP3R-3 单通道开放概率。将 Mz-ChA-1 细胞在高血糖培养基中孵育会导致内质网中依赖于 InsP3 的钙释放增加。O-GlcNAcylation 的动态和诱导特性以及 InsP3R 同工型特异性表明，InsP3R 的这种修饰形式以及随后的细胞内钙瞬变变化在生理和病理生理过程中很重要。
