Summary

Platelets are dynamic cell fragments that modify their shape duringactivation. Utrophin and dystrophins are minor actin-bindingproteins present in muscle and non-muscle cytoskeleton. In thepresent study, we characterised the pattern of Dp71 isoformsand utrophin gene products by immunoblot in human platelets.Two new dystrophin isoforms were found, Dp71f and Dp71d, aswell as the Up71 isoform and the dystrophin-associated proteins,a and ß -dystrobrevins. Distribution of Dp71d/Dp71δ₁₁₀^m ,Up400/Up71 and dystrophin-associated proteins in relation tothe actin cytoskeleton was evaluated by confocal microscopy in both resting and platelets adhered on glass. Formation of twodystrophin-associated protein complexes (Dp71d/Dp71δ₁₁₀^m~DAPC and Up400/Up71~DAPC) was demonstrated by co-immunoprecipitationand their distribution in relation to the actincytoskeleton was characterised during platelet adhesion. TheDp71d/Dp71δ₁₁₀^m ~DAPC is maintained mainly at the granulomereand is associated with dynamic structures during activationby adhesion to thrombin-coated surfaces.Participation ofboth Dp71d/Dp71δ₁₁₀^m~DAPC and Up400/Up71~DAPC in thebiological roles of the platelets is discussed.