Calmodulin-dependency of human neutrophil phosphodiesterase

Abstract
A recent study has reported that the phosphodiesterases of human neutrophils are calmodulin-insensitive (Smolen and Geosits,Inflammation 8:193–199, 1984). In the present study, two forms of human neutrophil phosphodiesterase were separated by chromatography on DEAE-52. Peak I phosphodiesterase is activated 2.3-fold by calcium and calmodulin but is not stimulated by either calcium or calmodulin alone. Calmodulin-dependent activation of the phosphodiesterase is blocked by both 20μM trifluoperazine and 20μM W-7. Peak II is not stimulated by calmodulin. These findings suggest that calmodulin may play an important role in regulating alterations in cyclic nucleotide metabolism that accompany neutrophil activation.