MG53-IRS-1 (Mitsugumin 53-Insulin Receptor Substrate-1) Interaction Disruptor Sensitizes Insulin Signaling in Skeletal Muscle

Abstract

Edited by Jeffrey PessinMitsugumin 53 (MG53) is an E3 ligase that interacts with and ubiquitinates insulin receptor substrate-1 (IRS-1) in skeletal muscle; thus, an MG53-IRS-1 interaction disruptor (MID), which potentially sensitizes insulin signaling with an elevated level of IRS-1 in skeletal muscle, is an excellent candidate for treating insulin resistance. To screen for an MID, we developed a bimolecular luminescence complementation system using an N-terminal luciferase fragment fused with IRS-1 and a C-terminal luciferase fragment fused with an MG53 C14A mutant that binds to IRS-1 but does not have E3 ligase activity. An MID, which was discovered using the bimolecular luminescence complementation system, disrupted the molecular association of MG53 with IRS-1, thus abolishing MG53-mediated IRS-1 ubiquitination and degradation. Thus, the MID sensitized insulin signaling and increased insulin-elicited glucose uptake with an elevated level of IRS-1 in C2C12 myotubes. These data indicate that this MID holds promise as a drug candidate for treating insulin resistance.Noninsulin-dependent diabetes mellitus (type 2 diabetes) has become a worldwide epidemic disease due to the increased incidence of obesity. Insulin receptor (IR) and insulin receptor substrate (IRS) 4 are inactivated by elevated serum levels of free fatty acids, leading to insulin resistance and noninsulin-dependent diabetes mellitus (1-3). Because skeletal muscle is the largest organ participating in glucose uptake, exercise-induced skeletal muscle development is an excellent treatment for insulin resistance. However, no current candidates target skeletal muscle to treat insulin resistance.Mitsugumin 53 (MG53), which is also called tripartite motifcontaining protein 72 (TRIM72) and which is largely expressed in skeletal muscle, was independently identified by proteomic analysis of lipid rafts and triad-rich membranes (4). MG53 contains a tripartite domain (an E3 ligase RING domain, a B-box, and two coiled-coil domains) and a SPRY domain. Insulin-like growth factor-1 (IGF-1) initiates MyoD activation via an IGF-1 receptor-PI3K-Akt pathway during skeletal myogenesis (5, 6). MyoD and myocyte enhancer factor 2 (MEF2) binds to two proximal E-boxes and an MEF2 site in MG53 promoter, activating MG53 gene transcription (7). The MG53 protein interacts with IRS-1 and focal adhesion kinase (FAK), inducing IRS-1 and FAK ubiquitination and degradation in skeletal muscle with the help of E2 ligase UBE2H (8 -10). Moreover, RING domain-disrupted MG53 mutants (⌬R and C14A) abolish IRS-1 and FAK ubiquitination and degradation in skeletal muscle, indicating that MG53 is an E3 ligase that targets IRS-1 and FAK.Systemic MG53 ablation abrogates IRS-1 ubiquitination and degradation in skeletal and cardiac muscle, leading to elevated IRS-1 expression level and increased insulin signaling (8, 9). Thus, MG53 knock-out mice do not develop diet-induced insulin resistance. In contrast, skeletal muscle-specific MG53 transgenic mice exhibit metabolic disorders such as obesity, ...

Infusion of adipose‑derived mesenchymal stem cells inhibits skeletal muscle mitsugumin 53 elevation and thereby alleviates insulin resistance in type 2 diabetic rats

“…The IRS family of proteins serves a central role in insulin signal transduction. Studies have demonstrated that elevated MG53 in skeletal muscle may ubiquitinate IRS-1 and subsequently decrease AKT phosphorylation, which is considered to be one important mechanism of insulin resistance in T2D or metabolic disorders (24,27). Thus, in the present study, the protein expression levels of insulin receptor, IRS-1 and p-AKT in skeletal muscle were analyzed to further confirm whether skeletal muscle MG53 may be a potential therapeutic target during the treatment of T2D by MSC infusion.…”

“…Therefore, the expression of MG53 in skeletal muscle during T2D should be investigated in greater detail. In addition, the aforementioned studies (19,24,27) identified that MSC infusion and MG53 may exert their effects via certain common molecules in the insulin signaling pathway, including IRS-1, AKT phosphorylation and Glut4, and our previous results indicated that MSC infusion inhibited MG53 elevation in the cardiac muscle of T2D rats (30). Therefore, it was hypothesized that MG53 in skeletal muscle may be a promising novel therapeutic target protein for MSC-mediated amelioration of insulin resistance in T2D.…”

“…Recent studies have demonstrated that the muscle-specific TRIM family protein mitsugumin 53 (MG53; also termed TRIM72) is implicated in insulin resistance (24)(25)(26)(27). In addition to acting as a key component of plasma membrane repair during normal cellular physiology (28,29), MG53 is also an E3 ligase that interacts with IRS-1 (24,25,27,29). Certain studies have demonstrated that MG53 expression is elevated in the skeletal muscle of rodents and humans with insulin resistance or metabolic disorders (24,27).…”

“…In addition to acting as a key component of plasma membrane repair during normal cellular physiology (28,29), MG53 is also an E3 ligase that interacts with IRS-1 (24,25,27,29). Certain studies have demonstrated that MG53 expression is elevated in the skeletal muscle of rodents and humans with insulin resistance or metabolic disorders (24,27). In addition, it has been indicated that elevated MG53 in skeletal muscle may interact with and ubiquitinated IRS-1, thereby disrupting insulin signaling and inducing insulin resistance or metabolic disorders (24,27).…”

“…Certain studies have demonstrated that MG53 expression is elevated in the skeletal muscle of rodents and humans with insulin resistance or metabolic disorders (24,27). In addition, it has been indicated that elevated MG53 in skeletal muscle may interact with and ubiquitinated IRS-1, thereby disrupting insulin signaling and inducing insulin resistance or metabolic disorders (24,27). Notably, the role of MG53 in metabolic disorders is controversial, as other studies have indicated that muscle samples derived from human diabetic patients and mice with insulin resistance exhibit normal expression of MG53 (25,26).…”