Platelet adhesion: Structural and functional diversity of short dystrophin and utrophins in the formation of dystrophin-associated-protein complexes related to actin dynamics

Platelets are dynamic cell fragments that modify their shape during activation. Utrophin and dystrophins are minor actin-binding proteins present in muscle and non-muscle cytoskeleton. In the present study, we characterised the pattern of Dp71 isoforms and utrophin gene products by immunoblot in human platelets. Two new dystrophin isoforms were found, Dp71f and Dp71d, as well as the Up71 isoform and the dystrophin-associated proteins, α and β -dystrobrevins. Distribution of Dp71d/Dp71Δ₁₁₀^m, Up400/Up71 and dystrophin-associated proteins in relation to the actin cytoskeleton was evaluated by confocal microscopy in both resting and platelets adhered on glass. Formation of two dystrophin-associated protein complexes (Dp71d/Dp71Δ₁₁₀^m -DAPC and Up400/Up71-DAPC) was demonstrated by co-immunoprecipitation and their distribution in relation to the actin cytoskeleton was characterised during platelet adhesion. The Dp71d/Dp71Δ₁₁₀^m-DAPC is maintained mainly at the granulomere and is associated with dynamic structures during activation by adhesion to thrombin-coated surfaces. Participation of both Dp71d/Dp71Δ₁₁₀^m-DAPC and Up400/Up71-DAPC in the biological roles of the platelets is discussed.