ClipR-59 Interacts with Akt and Regulates Akt Cellular Compartmentalization

Abstract

Akt is activated on the plasma membrane and its substrates are distributed throughout various cellular compartments. To phosphorylate its substrates, Akt needs to be recruited to specific intracellular compartments. Thus, regulation of Akt cellular compartmentalization constitutes an important mechanism to specify Akt signaling. Here, we report the identification of ClipR-59 as an Akt interaction protein. We show that the interaction of ClipR-59 with Akt is mediated by the CAP-Gly domain of ClipR-59 and kinase domain of Akt and is regulated by Akt phosphorylation. We demonstrate that ClipR-59 regulates the Akt membrane association through its interaction with Akt and membrane localization and, by modulating Akt cellular compartmentalization, differentially modulates phosphorylation of Akt substrates in adipocytes. Finally, we provide evidence that one of the Akt substrates whose phosphorylation is upregulated by ClipR-59 is AS160, a negative regulator of adipocyte glucose transport. Accordingly, ectopic expression of ClipR-59 enhances, whereas knockdown of ClipR-59 suppresses, adipocyte glucose transport. We suggest that ClipR-59 functions as a scaffold protein that interacts with phospho-Akt and recruits active Akt on the membrane and may play an important role in adipocyte glucose transport.

Gastric Inhibitory Peptide Controls Adipose Insulin Sensitivity via Activation of cAMP-response Element-binding Protein and p110β Isoform of Phosphatidylinositol 3-Kinase

“…Refs. 16,60,61). Perhaps GIP modulates Akt activity via alterations in localization or association with accessory proteins, mechanisms that would not be detected in total cell extract phosphorylation assays.…”

Elmo2 Is a Regulator of Insulin-dependent Glut4 Membrane Translocation

“…ClipR-59 interacts with Akt (19). We wondered whether Elmo2, ClipR-59, and Akt are in the same complex.…”

“…Elmo2 Regulates Glut4 Membrane Distribution in 3T3-L1 Adipocytes-Both ClipR-59 (19) and AS160 are involved in insulin-dependent Glut4 membrane translocation (23). The view that Elmo2 is in the same complex that includes AS160 and ClipR-59 promoted us to examine whether Elmo2 regulates insulin-dependent Glut4 membrane translocation.…”

“…The interaction between Akt and ClipR-59 is regulated by insulin (19). We therefore examined whether the interaction between Akt and Elmo2 is regulated by insulin.…”

“…A protein that regulates insulin-induced Akt membrane compartmentalization is the membraneassociated ClipR-59 (Clip (cytoplasmic linker protein)-related 59 kDa) (19). Once at the membrane, Akt phosphorylates a key substrate, AS160 (Akt substrate 160 kDa), which promotes Glut4 membrane redistribution.…”