Glycan microarrays for decoding the glycome

Abstract

In the last decade, glycan microarrays have revolutionized the analysis of the specificity of glycan-binding proteins (GBPs), providing information that simultaneously illuminates the biology mediated by them and decodes the informational content of the glycome. Numerous methods have emerged for arraying glycans in a "chip" format, and glycan libraries have been assembled that address the diversity of the human glycome. Such arrays have been successfully used for analysis of GBPs, which mediate mammalian biology, host-pathogen interactions, and immune recognition of glycans relevant to vaccine production and cancer antigens. This review covers the development of glycan microarrays and applications that have provided insights into the roles of mammalian and microbial GBPs.

Figure 1. Major classes of mammalian glycans

The major classes of mammalian glycans are depicted with the common core structures of each class boxed in grey. Sequences at the tips of the glycan chains are representative structural variations found in mammalian cells. Adapted from Reference (1).

Figure 2. Generation of Glycan Libraries

Common methods for generation of carbohydrate libraries for glycan arrays are shown. As shorthand, PG = protecting group, LG = leaving group, and GT = glycosyltransferase.

Figure 3. Reducing End Conjugation

Chemical methods for attachment of linkers to the reducing end aldehyde are shown along with the stereochemistry of the products generated by (A) reductive amination, (B) glycosylamine formation and trapping, (C) hydrazide chemistry, and (D) oxyamine or (E) N-alkyl oxyamine condensations. For (D) a ring-opened product is also formed as described in the text.

Figure 4. Methods for Immobilization of Glycans to Array Surfaces

Lettering corresponds to examples described in the accompanying text and the immobilization method used for arraying the various glycan libraries shown in Tables 1a/b.

Figure 5. Multivalent Binding Interactions on a Glycan Array Surface

Two representative examples, viral hemagglutinin (left) and DC-SIGN (right) are shown to illustrate the multivalency afforded by both the GBP and the array surface, leading to a stable interaction and subsequent detection.