Protein kinase A regulates β2 integrin avidity in neutrophils

The adhesive phenotype of neutrophils (PMN) depends largely on activating and deactivating intracellular signals regulating β2 integrin avidity for ligand. Our hypothesis is that PKA is a negative regulator of β2 integrin avidity. In this work, we examined the role of PKA in PMN αMβ2 integrin activation. Elevation of cAMP inhibited αMβ2 integrin-dependent adhesion of PMN to immune complexes (IC), but not PMA-induced adhesion. The PKA inhibitor KT5720 reversed the ability of cAMP to suppress adhesion to IC. Moreover, inhibition of PKA activity was sufficient to activate αMβ2 integrin-dependent adhesion and increase β2 integrin expression and binding of the monoclonal antibody CBRM1/5, which recognizes activated αMβ2 specifically. However, PKA activity was necessary for sustained adhesion. Disruption of A kinase-anchoring, protein-PKA binding with a cell-permeant peptide derived from the AKAP Ht31 also activated adhesion. Unlike pharmacologic inhibition of PKA, AKAP peptide-induced adhesion was PKC dependent and did not affect β2 integrin expression or CBRM1/5 binding. These data demonstrate that PKA appears to have a dual role in the mechanism regulating αMβ2 integrin avidity and adhesion.