Association of Dystrobrevin and Regulatory Subunit of Protein Kinase A: A New Role for Dystrobrevin as a Scaffold for Signaling Proteins

Abstract

The dystrophin-related and -associated protein dystrobrevin is a component of the dystrophin-associated protein complex, which directly links the cytoskeleton to the extracellular matrix. It is now thought that this complex also serves as a dynamic scaffold for signaling proteins, and dystrobrevin may play a role in this context. Since dystrobrevin involvement in signaling pathways seems to be dependent on its interaction with other proteins, we sought new insights and performed a two-hybrid screen of a mouse brain cDNA library using β-dystrobrevin, the isoform expressed in non-muscle tissues, as bait. Among the positive clones characterized after the screen, one encodes the regulatory subunit RIα of the cAMP-dependent protein kinase A (PKA). We confirmed the interaction by in vitro and in vivo association assays, and mapped the binding site of β-dystrobrevin on RIα to the amino-terminal region encompassing the dimerization/docking domain of PKA regulatory subunit. We also found that the domain of interaction for RIα is contained in the amino-terminal region of β-dystrobrevin. We obtained evidence that β-dystrobrevin also interacts directly with RIIβ, and that not only β-dystrobrevin but also α-dystrobrevin interacts with PKA regulatory subunits. We show that both α and β-dystrobrevin are specific phosphorylation substrates for PKA and that protein phosphatase 2A (PP2A) is associated with dystrobrevins. Our results suggest a new role for dystrobrevin as a scaffold protein that may play a role in different cellular processes involving PKA signaling.