Polarization is a critical mechanism for the proper functioning of many cell 
types. For lymphocytes, it is essential in a variety of processes, including 
migration from the blood to other tissue sites and vice versa. In NK cells and 
CTLs, the cytotoxic granule delivery mechanism requires polarization for granule 
movement to the immunological synapse (IS), in killing tumor and virus-infected 
cells. Recently, it has become apparent that endosomes are also involved in the 
cytotoxic mechanism. Using an in vitro conjugation approach, we show that in 
NK-92 cells, endosomal Sorting Nexin 27 (SNX27) polarizes to the IS during tumor 
cell engagement in a distinct compartment adjacent to the cytotoxic granules. We 
also show that SNX27 polarizes to the apical membrane, opposite the uropod, 
during NK cell migration. These previously unreported results indicate that 
SNX27 is a participant in NK cell polarization, as a mediator or target of the 
mechanism.