Distribution and lateral mobility of DC-SIGN on immature dendritic cells–implications for pathogen uptake

Abstract

The receptor C-type lectin DC-SIGN (CD209) is expressed by immature dendritic cells, functioning as an antigen capture receptor and cell adhesion molecule. Various microbes, including HIV-1, can exploit binding to DC-SIGN to gain entry to dendritic cells. DC-SIGN forms discrete nanoscale clusters on immature dendritic cells that are thought to be important for viral binding. We confirmed that these DC-SIGN clusters also exist both in live dendritic cells and in cell lines that ectopically express DC-SIGN. Moreover, DC-SIGN has an unusual polarized lateral distribution in the plasma membrane of dendritic cells and other cells: the receptor is preferentially localized to the leading edge of the dendritic cell lamellipod and largely excluded from the ventral plasma membrane. Colocalization of DC-SIGN clusters with endocytic activity demonstrated that surface DC-SIGN clusters are enriched near the leading edge, whereas endocytosis of these clusters occurred preferentially at lamellar sites posterior to the leading edge. Therefore, we predicted that DC-SIGN clusters move from the leading edge to zones of internalization. Two modes of lateral mobility were evident from the trajectories of DC-SIGN clusters at the leading edge, directed and non-directed mobility. Clusters with directed mobility moved in a highly linear fashion from the leading edge to rearward locations in the lamella at remarkably high velocity (1420±260 nm/second). Based on these data, we propose that DC-SIGN clusters move from the leading edge–where the dendritic cell is likely to encounter pathogens in tissue–to a medial lamellar site where clusters enter the cell via endocytosis. Immature dendritic cells may acquire and internalize HIV and other pathogens by this process.

Cytoplasmic Trafficking, Endosomal Escape, and Perinuclear Accumulation of Adeno-Associated Virus Type 2 Particles Are Facilitated by Microtubule Network

“…Movements over such short distance (several micrometers) might be achieved by normal diffusion. Internalization in the sites around the nucleus can be achieved by the direct binding of viral particles at these sites (our unpublished data) or by viral surfing on the cell membrane to these sites (34). Our studies do not exclude the possibility that AAV2 particles may reach the nucleus through a much slower process by exploiting actin filaments or intermediate filaments (35,43).…”

The C‐type lectin DC‐SIGN internalizes soluble antigens and HIV‐1 virions via a clathrin‐dependent mechanism

“…Recently, we demonstrated that on the plasma membrane of DC, DC-SIGN is organized in nanoclusters, some of which colocalize with lipid rafts, that specifically confer to the receptor its capacity of binding and internalizing viruses as well as Ag conjugated to fluorescent nanoparticles [9,10]. These findings were substantiated by a biophysical study by Neumann et al, who showed that these nanoclusters are enriched near the leading edge of living DC, but are preferentially endocytosed at lamellar sites posterior to the leading edge, suggesting a directed mobility of DC-SIGN from areas of concentration at the front to rearward sites of internalization [11].…”

A New Tool to Quantify Receptor Recruitment to Cell Contact Sites during Host-Pathogen Interaction

“…These domains have interesting biophysical properties, such as a lack of exchange of receptor with the surrounding membrane and nearly complete segregation of DC-SIGN and CD206 nanodomains in resting DC membranes [68]–[70]. Recently, we have observed that nanoscale organization of CTLs in fungal contacts is altered relative to non-contact membrane in favor of less individual nanodomain structure and more longer-range nanostructure, consistent with close packing of domains (unpublished data, AKN).…”