生物谷报道：美国科学家在6月号的《自然—化学生物学》（Nature Chemical Biology）上发表最新文章说，脑部刺激会导致神经细胞内蛋白质糖分含量的变化，这意味着糖修饰可能是大脑信号传输的一个重要使者。
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众所周知，在细胞信号的传输中，丝氨酸和苏氨酸残基的磷酸化水平的变化发挥了作用。糖基化是糖基吸附在蛋白质上而导致其性能改变的一种作用。虽然绝大部分糖基化发生在细胞外的蛋白质上，但一种名为O位N-乙酰葡萄糖胺(O-GlcNAc)的糖基修饰却吸附在细胞外蛋白质的丝氨酸和苏氨酸残基上。
因为磷酸化和O-GlcNAc修饰均严格发生在同一氨基酸的侧链上，所以，O-GlcNAc对细胞的信号传输来说应该十分重要。但是，科学家们一直缺少在活体内精确鉴别O-GlcNAc修饰的工具，因而很难对这一假说进行验证。
Linda Hsieh-Wilson和同事发明了一种蛋白质组学方法，利用质谱分析法确定活体中O-GlcNAc的水平。当他们将一种兴奋剂注入小鼠体时，他们在小鼠大脑中的特定位置发现了糖水平的变化。利用这些信息，科学家们就有可能研究O-GlcNAc在大脑功能中的确切作用了。
原始出处:
Nature Chemical Biology 3, 339-348 (2007)
doi:10.1038/nchembio881
Probing the dynamics of O-GlcNAc glycosylation in the brain using quantitative proteomics
Nelly Khidekel1, Scott B Ficarro2, Peter M Clark1, Marian C Bryan1, Danielle L Swaney3, Jessica E Rexach4, Yi E Sun4, Joshua J Coon3, Eric C Peters2 & Linda C Hsieh-Wilson1
Abstract
The addition of the monosaccharide -N-acetyl-D-glucosamine to proteins (O-GlcNAc glycosylation) is an intracellular, post-translational modification that shares features with phosphorylation. Understanding the cellular mechanisms and signaling pathways that regulate O-GlcNAc glycosylation has been challenging because of the difficulty of detecting and quantifying the modification. Here, we describe a new strategy for monitoring the dynamics of O-GlcNAc glycosylation using quantitative mass spectrometry-based proteomics. Our method, which we have termed quantitative isotopic and chemoenzymatic tagging (QUIC-Tag), combines selective, chemoenzymatic tagging of O-GlcNAc proteins with an efficient isotopic labeling strategy. Using the method, we detect changes in O-GlcNAc glycosylation on several proteins involved in the regulation of transcription and mRNA translocation. We also provide the first evidence that O-GlcNAc glycosylation is dynamically modulated by excitatory stimulation of the brain in vivo. Finally, we use electron-transfer dissociation mass spectrometry to identify exact sites of O-GlcNAc modification. Together, our studies suggest that O-GlcNAc glycosylation occurs reversibly in neurons and, akin to phosphorylation, may have important roles in mediating the communication between neurons.
Division of Chemistry and Chemical Engineering and Howard Hughes Medical Institute, California Institute of Technology, Pasadena, California 91125, USA.
Genomics Institute of the Novartis Research Foundation, San Diego, California 92121, USA.
Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Mental Retardation Research Center, Department of Psychiatry and Biobehavioral Sciences and Department of Molecular and Medical Pharmacology, and Neuropsychiatric Institute, The David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA.
Correspondence to: Linda C Hsieh-Wilson1 Email: lhw@caltech.edu
