Neutrophil leukocyte motility requires directed water influx

Abstract: The ability of neutrophils to sense and move to sites of infection is essential for our de-fense against pathogens. For motility, lamellipo-dium extension and stabilization are prerequisites, but how cells form such membrane protrusions is still obscure. Using contrast-enhanced video mi-croscopy and Transwell assays, we show that wa-ter-selective aquaporin channels regulate lamelli-podium formation and neutrophil motility. Addi-tion of anti-aquaporin-9 antibodies, HgCl2, or tetraethyl ammonium inhibited the function(s) of the channels and blocked motility-related shape changes. On human neutrophils, aquaporin-9 pref-erentially localized to the cell edges, where N-formyl peptide receptors also accumulated, as assessed with fluorescence microscopy. To directly visualize water fluxes at cell edges, cells were loaded with high dilution-sensitive, self-quenching concentrations of fluorophore. In these cells, mo-tile regions always displayed increased fluores-cence compared with perinuclear regions. Our ob-servations provide the first experimental support for motility models where water fluxes play a piv-otal role in cell-volume increases accompanyin