Requirement for protein kinase A in the phosphorylation of the TGFβ receptor-interacting protein km23-1 as a component of TGFβ downstream effects

► km23-1 is phosphorylated by PKA at serine 73 both in vitro and in vivo. ► TGFβ regulates km23-1 interaction with the R1β regulatory subunit of PKA. ► km23-1 synergizes with the TGFβ ligand-receptor complex to stimulate the CRE. ► PKA phosphorylation of km23-1 is required for TGFβ induction of FN transcription. ► km23-1 mediates signaling cross-talk between PKA, JNK/CRE, and Smad2 pathways.