Inhibition of actin-dystrophin interaction by inositide phosphate

Dystrophin, the protein absent from Duchenne dystrophy, is a member of the alpha-actinin protein family and located in the membrane cytoskeleton. It bridges a transmembrane glycoprotein complex with actin filaments. This work investigates the binding of dystrophin issued from Torpedo marmorata electric organ with actin in the presence of the phosphoinositide PIP2 that regulates alpha-actinin and filamin binding with actin. The interaction was inhibited (80%) by PIP2 and reached its minimum above 20 microM PIP2, but the effect was abolished when PIP2 was previously cleaved by phospholipase C. Using antibodies directed against the 27 kDa actin binding domain of alpha-actinin, a reliable carrier for actin binding sites ABS-1, ABS-2 and ABS-3 also involved in dystrophin and filamin, it was shown that PIP2 affects the ABS-3 environment.