Methods for Investigating Siglec-Ganglioside Interactions

Siglecs are a family of cell surface receptors generally found on immune cells, which are important in many cellular processes such as cell-adhesion, cell-signaling, and internalization of extracellular particles. While all these smaller functions play a part in larger and different physiological roles, one aspect they share is that they are initiated by the binding of a Siglec to its ligand. Siglec ligands are cell-surface carbohydrates appended to proteins and lipids that terminate with the monosaccharide sialic acid. The functions of a Siglec are directly linked to the binding of its ligands. There has been a great effort by many research teams over the past three decades to describe Siglec ligands to better understand their roles in health and disease. The systematic description of Siglec ligands has revealed that Siglecs are important in a range of physiological processes, including but not limited to allergies, antibody production, cancer progression, and reproduction. However, despite these efforts, the description of Siglec ligands remains incomplete. Historically Siglec-glycoprotein interactions have been better described compared to Siglec-glycolipid interactions; this is likely due to the combination of the relative difficulty in studying Siglec-glycolipid interactions and the dearth of tools available to study these interactions. Gangliosides are the major class of sialylated glycolipids in mammals. In this chapter, three protocols used to investigate Siglec-ganglioside interactions are described; these methods can be applied to further our understanding of gangliosides as Siglec ligands and the physiological and pathophysiological roles that they mediate.