Langerin, a C-type lectin is expressed in Langerhans cells. It was reported that langerin binds sulfated glycans, which is an important initial step for its role in blocking human immunodeficiency virus (HIV) transmission by capturing HIV pathogens and mediating their internalization into Birbeck Granules for their elimination. It is fundamentally important to understand these interactions at the molecular level for the design of new highly specific therapeutic agents for HIV. Surface plasmon resonance (SPR), which allows for the real-time, direct, quantitative analysis of the label-free molecular interactions, has been used successfully for biophysical characterization of glycosaminoglycan (GAG)-protein interactions. In the current study, we report kinetics, structural analysis, and the effects of physiological conditions (e.g., pH, salt concentration, Ca2+ and Zn2+concentration) on the interactions between GAGs and langerin using SPR. SPR results revealed that langerin binds to heparin with high affinity (KD~2.4 nM) and the oligosaccharide length required for the interactions is larger than a tetrasaccharide. This heparin/heparan sulfate binding protein also interacts with other GAGs including, dermatan sulfate, and chondroitin sulfates C, D, and E and KS. In addition, liquid chromatography-mass spectrometry was used to characterize the structure of sulfated glycans that bound to langerin.
Kinetic and Structural Studies on Interactions between Glycosaminoglycans and Langerin.