Adducin α Background Information
Adducins are a family of cytoskeleton proteins encoded by three genes (a, b and g). Adducin is a protein associated with the inner leaflet of the plasma membrane and is one of the proteins localized at the spectrin-actin junction of the membrane skeleton. Adducins promote association of spectrin with actin and cap the fast growing end of actin filaments. Adducins contain an N-terminal core, neck and C-terminal tail domains, are substrates for protein kinase A (PKA) and C (PKC), and bind to Ca2+/calmodulin. The major phosphorylation sites common to the Adducins are Ser 726 and Ser 713 in the C-terminal MARCKS-related domains of Adducin a and Adducin b, and they are phosphorylated by PKA and PKC, respectively. In addition, PKA phosphorylates Adducin a at Ser 408, 436 and 481. Calmodulin-binding is inhibited by phosphorylation of Adducin b that, in turn, inhibits the rate of phospho-rylation of Adducin b, but not Adducin a. Rho-kinase can phosphorylate Adducin a at Thr 445 and Thr 480 downstream of Rho in vivo. The phosphorylation of Adducin by Rho-kinase plays an important role in the regulation of membrane ruffling and cell motility. In addition, phosphorylation at Ser 726 of Adducin a is required for cleavage by caspase-3 .
