miR-24-3p down-regulates the expression of the apoptotic factors FasL and BIM in human natural killer cells

MicroRNAs are involved in the regulation of different functions in immune and non-immune cells. Here we show that miR-24-3p functionally interacts with FASLG mRNA and down-regulates its expression. This interaction occurs in human natural killer cells (NK), leading to the modulation of FasL surface expression. Moreover, miR-24-3p also modulates the mRNA and protein expression of BIM in NK cells. Thus, it likely contributes to the control of both the extrinsic and intrinsic apoptotic pathways. In line with this hypothesis, inhibition of miR-24-3p improves both initiator caspase-8 and effector caspase-3 and -7 activities, increases cell apoptosis, and reduces cell viability. Our data suggest that miR-24-3p can act as a survival factor in NK cells, affecting the FasL-mediated killing of Fas expressing cells and the BIM-dependent cell death. More generally, miR-24-3p may condition the level of cell apoptosis, which increases at the contraction phase of the immune response when the clearance of various expanded effector cells is needed.