Mapping nano-landscape of pathogen recognition receptor DC-SIGN and lipid rafts on dendritic cells

The dendritic cell (DC) specific pathogen-recognition receptor DCSIGN binds and internalizes antigens for degradation. The organization of DC-SIGN in microdomains is crucial for the binding and the internalization of virus particles, suggesting that these multimolecular assemblies act as docking site for pathogens like HIV-1 to invade the host. We have recently shown that DC-SIGN potentially associates with lipid rafts [1] and clathrin coated pits [2]. Nevertheless, the nano-scale organization of DC-SIGN with respect to these lipid domains remains largely unresolved. To map the nanolandscape distribution of DC-SIGN on DC cell membranes we are exploiting state-of-the-art microscopic imaging techniques. Single fluorescent molecule detection together with multicolor labeling offers the possibility to elucidate organization and co-localization at <100 nm spatial resolution. Currently we are investigating the potential association of DC-SIGN with lipid rafts using a near-field optical microscope working under physiological conditions. Additionally we are planning a three color experiment to resolve the nano-landscape of DC-SIGN, lipid rafts and clathrin coated pits before and during endocytosis. The possible change in organization and association of DC-SIGN is essential for the understanding of the antigen uptake mechanism(s) from the membrane of DCs. [1] A. Cambi, et al., Journal of Cell Biology, 164 , 145 (2004). [2] A. Cambi, et al., Nanoletters, In Press.