The dynamic brain N-glycome

The attachment of carbohydrates to other macromolecules, such as proteins or lipids, is an important regulatory mechanism termed glycosylation. One subtype of protein glycosylation is asparagine-linked glycosylation (N-glycosylation) which plays a key role in the development and normal functioning of the vertebrate brain. To better understand the role of N-glycans in neurobiology, it's imperative we analyse not only the functional roles of individual structures, but also the collective impact of large-scale changes in the brain N-glycome. The systematic study of the brain N-glycome is still in its infancy and data are relatively scarce. Nevertheless, the prevailing view has been that the neuroglycome is inherently restricted with limited capacity for variation. The development of improved methods for N-glycomics analysis of brain tissue has facilitated comprehensive characterisation of the complete brain N-glycome under various experimental conditions on a larger scale. Consequently, accumulating data suggest that it's more dynamic than previously recognised and that, within a general framework, it has a given capacity to change in response to both intrinsic and extrinsic stimuli. Here, we provide an overview of the many factors that can alter the brain N-glycome, including neurodevelopment, ageing, diet, stress, neuroinflammation, injury, and disease. Given this emerging evidence, we propose that the neuroglycome has a hitherto underappreciated plasticity and we discuss the therapeutic implications of this regarding the possible reversal of pathological changes via interventions. We also briefly review the merits and limitations of N-glycomics as an analytical method before reflecting on some of the outstanding questions in the field.