CD98hc, a novel of galectin-8 receptor, binds to galectin-8 in an N-glycosylation-dependent manner

Glycan-mediated recognition plays a critical role in facilitating cell-cell and cell-matrix interactions. Galectin-8 (Gal-8), classified as a 'tandem-repeat' type of galectin, binds to cell surface glycans to modulate various cellular functions, including cell adhesion, migration, apoptosis, pathogen recognition, autophagy, and immunomodulation. Despite the known function of Gal-8 in binding to various glycosylated proteins, only a few interactions have been reported to date. In this study, mass spectrometry is used to identify CD98hc as a novel binding partner for Gal-8. Both the N-terminal and C-terminal carbohydrate recognition domains (CRDs) of Gal-8 (Gal-8N and Gal-8C) bind to CD98hc, an interaction that is specifically inhibited by lactose but not sucrose, as confirmed by pull-down assays. The binding affinity between CD98hc and Gal-8 measured by microscale thermophoresis (MST) is 1.51 ± 0.17 microM. In addition, Gal-8N and Gal-8C have the binding affinities of 0.22 ± 0.03 microM and 10.68 ± 1.69 microM, respectively. Gal-8N and Gal-8C are both involved in the recognition and binding process of CD98hc. Furthermore, both full-length Gal-8 and its individual CRDs bind specifically to N-glycosylated glycans on CD98hc, as demonstrated by the use of tunicamycin to inhibit N-glycosylation in cells. In addition, Gal-8 and its individual CRDs can pull down glycosylated CD98hc-ED but not free CD98hc-ED in vitro, indicating that the binding of Gal-8 to glycosylated CD98hc-ED is N-glycosylation-dependent. Overall, our findings establish CD98hc as a novel binding partner for Gal-8 and provide insights for further exploration of the diverse biological functions of Gal-8.