Encoding Cell-Surface Receptor Function Through Glycosylation: Lessons From CD44.

Cell surface receptors are traditionally conceptualized as discrete molecular entities whose functional diversity arises primarily from gene expression and protein sequence variation. However, this view overlooks the extensive heterogeneity generated by post-translational modifications, particularly glycosylation, which can profoundly alter receptor structure, dynamics, and interactions. Increasing evidence suggests that glycosylation does not simply fine-tune receptor activity but rather defines distinct functional receptor states by modulating ligand recognition, nanoscale organization, interaction networks, and signaling competence. Among glycosylated receptors, CD44 provides a particularly informative model due to its extensive alternative splicing, dense glycosylation, and well-characterized interactions with the extracellular matrix. CD44 exhibits remarkable structural and functional plasticity and regulates diverse biological processes ranging from cell adhesion and migration to inflammation and cancer progression. Importantly, glycosylation influences CD44 interactions with its principal ligand, hyaluronan, as well as its ability to cluster, engage coreceptors, and initiate downstream signaling pathways. In this review, we discuss how glycosylation regulates CD44 function across multiple levels, from molecular recognition to membrane organization and signaling. Using CD44 as a paradigmatic example, we explore how glycosylation may shape distinct aspects of receptor function, underscoring its importance as a fundamental determinant of receptor biology and its relevance for therapeutic targeting.