Daxx functions as a scaffold of a protein assembly constituted by GLUT4, JNK1 and KIF5B.

We have previously reported the physical interaction between Daxx, the adaptor protein that mediates activation of the Jun amino-terminal kinase (JNK), and GLUT4, the insulin-dependent glucose transporter, interaction that involves their C-domains. Co-immunoprecipitation and two-hybrid-based protein-protein interaction studies show now that Daxx and GLUT4 interact with JNK1 through D-sites in their NH(2)-(aa 1-501) and large endofacial loop, respectively. Serum deprivation strongly enhances the association of JNK1 with Daxx and dissociates the kinase from GLUT4. SP600125, a potent JNK1 inhibitor, reduces the JNK1 activity associated with GLUT4 and the phosphorylation of two minor GLUT4 species in serum-starved 3T3-L1 adipocytes. In addition, Daxx interacts with kinesin KIF5B through the 6xTPR domain of the kinesin light chain, a domain engaged in the grab hold of protein cargo by kinesin motors that codistribute with JNK. Depletion of Daxx in 3T3-L1 adipocytes provokes the partial translocation of the GLUT4 retained in the GLUT4 storage compartment to endosomes.