Nucleocapsid Promotes Localization of HIV-1 gag to uropods that participate in virological synapses between T Cells

T cells adopt a polarized morphology in lymphoid organs,where cell-to-cell transmission of hiv-1 is likely frequent. however,despite the importance of understanding virus spread in vivo,little is known about the hiv-1 life cycle,particularly its late phase,in polarized t cells. polarized t cells form two ends,the leading edge at the front and a protrusion called a uropod at the rear. using multiple uropod markers,we observed that hiv-1 gag localizes to the uropod in polarized t cells. infected t cells formed contacts with uninfected target t cells preferentially via hiv-1 gag-containing uropods compared to leading edges that lack plasma-membrane-associated gag. cell contacts enriched in gag and cd4,which define the virological synapse (vs),are also enriched in uropod markers. these results indicate that gag-laden uropods participate in the formation and/or structure of the vs,which likely plays a key role in cell-to-cell transmission of hiv-1. consistent with this notion,a myosin light chain kinase inhibitor,which disrupts uropods,reduced virus particle transfer from infected t cells to target t cells. mechanistically,we observed that gag copatches with antibody-crosslinked uropod markers even in non-polarized cells,suggesting an association of gag with uropod-specific microdomains that carry gag to uropods. finally,we determined that localization of gag to the uropod depends on higher-order clustering driven by its nc domain. taken together,these results support a model in which nc-dependent gag accumulation to uropods establishes a preformed platform that later constitutes t-cell-t-cell contacts at which hiv-1 virus transfer occurs. © 2010 llewellyn et al.