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Educated natural killer cells show dynamic movement of the activating receptor NKp46 and confinement of the inhibitory receptor Ly49A
Staaf, E., Hedde, P. N., Bagawath Singh, S., Piguet, J., Gratton, E., & Johansson, S.
Educated natural killer (NK) cells possess inhibitory receptors specific for self major histocompatibility (MHC) class I molecules and kill cancer cells more efficiently than NK cells not possessing such receptors (from hereon referred to as hyporesponsive NK cells). The mechanism behind this functional empowerment through education has so far not been fully described. In addition, distinctive phenotypical markers of educated NK cells at the single cell level are lacking. We developed a refined version of the image mean square displacement (iMSD) method, called iMSD carpet analysis, and used it in combination with single-particle tracking to characterize the dynamics of the activating receptor NKp46 and the inhibitory receptor Ly49A on resting educated versus hyporesponsive murine NK cells. The majority of both NKp46 and Ly49A molecules were restricted to microdomains; however, individual NKp46 molecules resided in these domains for shorter periods and diffused faster on the surface of educated, compared to hyporesponsive, NK cells. In contrast, the movement of Ly49A was more constrained in educated NK cells compared to hyporesponsive NK cells. Either disrupting the actin cytoskeleton or adding cholesterol to the cells prohibited activating signaling, indicating that the dynamics of receptor movements within the cell membrane are critical for proper activation of NK cells. The faster and more dynamic movement of NKp46 in educated NK cells may facilitate a swifter response in interactions with target cells.