Asymmetrical protein kinase A activity establishes neutrophil cytoskeletal polarity and enables chemotaxis

Neutrophil chemotaxis requires precise spatial organization of the actin cytoskeleton and integrin activation to polarize the cell and enable migration. Protein kinase A (PKA) activity regulates integrin activation and actin cytoskeletal organization, suggesting that PKA is a key element in the mechanism regulating neutrophil chemotaxis. Our hypothesis is that asymmetrical PKA activity is critical for establishing neutrophil adhesive and cytoskeletal polarity required for migration during chemotaxis. To test this hypothesis, we first determined that global treatment with the PKA inhibitor KT5720 decreased formylated Met-Leu-Phe (fMLF)-induced migration. The ability of PKA inhibitors to reduce migration correlated with increased overall beta2 integrin cell-surface expression, affinity activation, and cellular adhesion. We next determined whether asymmetrical PKA activity was sufficient to induce migration. Exposure to gradient of the PKA inhibitors KT5720 or H-89 or a stearated, cell-permeant peptide (St-Ht31), which inhibits PKA binding to anchorage proteins, stimulated neutrophil migration in a chemotaxis chamber. Global treatment with KT5720 abolished the ability of fMLF to polarize the neutrophil actin cytoskeleton. In contrast to global treatment with KT5720, a point source of KT5720 was sufficient to polarize the actin cytoskeleton. The ability of KT5720 and St-Ht31 to stimulate migration was abolished by pretreatment with the phosphatidylinositol-3 kinase (PI-3K) inhibitors wortmannin and LY294002. These data suggest that asymmetrical PKA activity is necessary and sufficient for actin cytoskeletal polarization and migration during neutrophil chemotaxis. In addition, our data suggest PI-3K is an effector of PKA during chemotaxis.