Rho-Associated Kinase Phosphorylates Desmin, the Myogenic Intermediate Filament Protein, at Unique Amino-Terminal Sites☆

Abstract We obtained evidence that Rho-associated kinase (Rho-kinase) phosphorylates desmin, the myogenic intermediate filament protein, with approximately 2 mol phosphate per mole of desmin in vitro. Desmin phosphorylated by Rho-kinase lost the potential to form 10-nm filaments. Thr-16, Thr-75, and Thr-76 on desmin proved to be the major phosphorylation sites for Rho-kinase. All these sites are located within the head domain and are different from the reported phosphorylation sites of protein kinase A, protein kinase C, and cdc2 kinase. We are entertaining the notion that Rho-kinase may regulate filament structures of desmin by site-specific phosphorylation.