An evolutionary perspective of the roles of galectins in pathogen recognition and immunity

Protein-glycan interactions, mediated by lectins, are essential for diverse physiological processes, including glycoprotein processing, cell adhesion, communication, signaling, and immune recognition. Lectins, classified into families like C-type, I-type, F-type, and galectins, recognize specific glycans on macromolecules through their carbohydrate recognition domains (CRDs). Galectins, characterized by their β-galactoside binding and conserved CRD structure, exhibit remarkable functional diversification across evolution. Initially associated with developmental roles, they are now implicated in cancer, angiogenesis, and immune homeostasis. Furthermore, they interact with glycans on both beneficial and pathogenic microorganisms. While host galectins facilitate mutualistic interactions, pathogens can exploit this recognition for infection and manipulate host glycosylation to subvert galectin functions. The ability of galectins to recognize both self and non-self glycans, evident even in early metazoans, underscores their evolutionary versatility and raises questions about their primordial function and their evolutionary trajectory. This review explores the evolving roles of galectins, highlighting their adaptability and the complex interplay between host and pathogen interactions.