Interactome Mapping: Using Protein Microarray Technology to Reconstruct Diverse Protein Networks

Uzoma, Ijeoma; Zhu, Heng

Cell surface glycosylation is a complex and highly-varied PTM that in turn is not amenable to standard high-throughput techniques. Glycosylation is present on the surface of all vertebrate cells, and it serves to distinguish cell types through very delicate differences [9] . It is also shown to be associated with cell differentiation, malignant transformation and subcellular localization [61] [62] [63] [64] [65] . Glycan binding proteins, known as lectins, are used to characterize glycosylation marks due to their ability to discriminate sugar isoforms [66] . Lectin microarrays have already been employed to characterize glycoproteins and lysates [67, 68] , however, they have not been used to systematically profile cell surface glycosylation signatures of mammalian cell types. Such studies have the potential to provide a tool for distinguishing normal versus abnormal cell surface profiles based on glycan-lectin interactions. Tao et al. fabricated a lectin microarray composed of 94 non-redundant lectins selected for defining cell surface glycan signatures [5] . Using 23 well-studied mammalian cell lines, the authors developed a systematic binary analysis of binding interactions of the selected lectins and cell types. They observed a broad range of binding potential and specificity across cell types, implying a high level of variation in cell surface glycans within mammalian cell types. For example, less than 20 lectins could capture the hESC, Caco-2, D407 and U937 cells, while more than 50 lectins captured the HEK293, K1106 and MCF7 cells [9] . Interestingly, similar cell types such as various breast cancer cell lines did not reveal overlapping lectin binding profiles, indicating lectins can discern subtle differences between physiologically-related cells.