ClC-3 and IClswell are Required for Normal Neutrophil Chemotaxis and Shape Change^*

Abstract

Polymorphonuclear leukocytes undergo directed movement to sites of infection, a complex process known as chemotaxis. Extension of the polymorphonuclear leukocyte (PMN) leading edge toward a chemoattractant in association with uropod retraction must involve a coordinated increase/decrease in membrane, redistribution of cell volume, or both. Deficits in PMN phagocytosis and trans-endothelial migration, both highly motile PMN functions, suggested that the anion transporters, ClC-3 and ICl_swell, are involved in cell motility and shape change (

). We hypothesized that ClC-3 and ICl_swell are required for normal PMN chemotaxis through regulation of cell volume and shape change. Using complementary chemotaxis assays, EZ-TAXIScan™ and dynamic imaging analysis software, we analyzed the directed cell movement and morphology of PMNs lacking normal anion transporter function. Murine Clcn3^-/- PMNs and human PMNs treated with anion transporter inhibitors demonstrated impaired chemotaxis in response to formyl peptide. This included decreased cell velocity and failure to undergo normal cycles of elongation and retraction. Impaired chemotaxis was not due to a diminished number of formyl peptide receptors in either murine or human PMNs, as measured by flow cytometry. Murine Clcn3^-/- and Clcn3^+/+ PMNs demonstrated a similar regulatory volume decrease, indicating that the ICl_swell response to hypotonic challenge was intact in these cells. We further demonstrated that ICl_swell is essential for shape change during human PMN chemotaxis. We speculate that ClC-3 and ICl_swell have unique roles in regulation of PMN chemotaxis; ICl_swell through direct effects on PMN volume and ClC-3 through regulation of ICl_swell.