DC-SIGN Mediated Dengue Virus Entry into Cells

Abstract

DC-SIGN (a single-pass, C-type lectin, transmembrane protein) is a receptor for dengue virus (DENV) and variety of other pathogens. It exists in small clusters on the plasma membranes of dendritic and other immune cells. Using NIH3T3 cells that express full length DC-SIGN or a mutant form lacking the cytoplasmic tail as well as primary human immature dendritic cells, we investigated DENV binding, surface transport, endocytosis and infection. We employed confocal microscopy, super-resolution imaging and large-scale single particle tracking. After binding, the virus/receptor complexes co-migrate to clathrin coated pits where the complexes are endocytosed followed by release of the viral genome for replication. Suprisingly, dengue binding, even to a few DC-SIGN clusters, induces a global cellular response in which both loaded and unloaded DC-SIGN clusters exhibit dramatically increased lateral mobility, possibly to enhance encounters with coated pits. In addition, a small but significant fraction of DC-SIGN clusters in the plasma membrane undergo rapid, microtubule-based directed transport towards the cell center at velocities which can exceed 1μm/s. Since the measured velocities are increased after dengue binding, this activity may be required to bring captured pathogens from the leading margins back to perinuclear zone for processing by dendritic cells. A controversy exists as to whether DC-SIGN functions simply as an attachment factor for dengue viruses or whether it plays additional roles in viral entry. The absence of the DC-SIGN cytoplasmic region reduced both dengue binding and endocytosis. However, infection still occurred, albeit reduced, suggesting that DC-SIGN must be able to act in concert with a co-receptor containing cell entry motifs. Supported by NIH GM41402.