OP-1：The role of NEMO (NF-κB essential modulator, IKKγ) in TNF-α induced insulin resistance in 3T3-L1 adipocytes

Yukio Tanizawa , Masahiro Emoto, Naofumi Fukuda, Akihiko Taguchi, Shigeru Okuya and Yoshitaka Nakamori

Division of Molecular Analysis of Human disorders, Department of Bio-Signal Analysis

Yamaguchi University Graduate School of Medicine

The IKK complex contains two protein kinases IKK-α and IKK-β, and a regulatory subunit NEMO (IKKγ). It was previously reported that IKK-β directly phosphorylates IRS-1 at Ser³⁰⁷ with stimulation of TNF-α. This Ser phosphorylation of IRS-1 diminishes its insulin-stimulated tyrosine phosphorylation, and attenuates insulin signal transduction. However, little is known about the role of NEMO subunits on the TNF-α induced insulin resistance.

To evaluate the role of NEMO, we measured basal and insulin stimulated glucose uptake in 3T3-L1 adipocytes which transiently expressed wild type, or N-terminal deletion mutant of NEMO using adenovirus-mediated gene transfer system. This deletion mutant prevents the IKK complex formation. We also measured glucose uptake after the reduction of NEMO expression by siRNA.

Overexpression of wild type NEMO induced the IRS-1 phosphorylation at Ser³⁰⁷ without TNF-α, and decreased insulin stimulated glucose uptake. On the other hands, overexpression of the deletion mutant or silencing of NEMO expression prevented TNF-α induced IRS-1 Ser³⁰⁷ phosphorylation, and increased insulin stimulated glucose uptake by 80% and 70%, respectively in the presence of TNF-α.

These findings indicate that NEMO may have important roles on TNF-α induced insulin resistance.