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Ruisheng Song,
Wei Peng,
Yan Zhang,
Fengxiang Lv,
Hong-Kun Wu,
Jiaojiao Guo,
Yongxing Cao,
Yanbin Pi,
Xin Zhang,
Li Jin,
Mao Zhang,
Peng Jiang,
Fenghua Liu,
Shaoshuai Meng,
Xiuqin Zhang,
Ping Jiang,
Chun-Mei Cao,
Rui-Ping Xiao
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ABSTRACT: Insulin resistance is a fundamental pathogenic factor present in various metabolic disorders including obesity and type 2 diabetes. Although skeletal muscle accounts for 70-90% of insulin-stimulated glucose disposal, the mechanism underlying muscle insulin resistance is poorly understood. Here we show in mice that muscle-specific mitsugumin 53 (MG53; also called TRIM72) mediates the degradation of the insulin receptor and insulin receptor substrate 1 (IRS1), and when upregulated, causes metabolic syndrome featuring insulin resistance, obesity, hypertension and dyslipidaemia. MG53 expression is markedly elevated in models of insulin resistance, and MG53 overexpression suffices to trigger muscle insulin resistance and metabolic syndrome sequentially. Conversely, ablation of MG53 prevents diet-induced metabolic syndrome by preserving the insulin receptor, IRS1 and insulin signalling integrity. Mechanistically, MG53 acts as an E3 ligase targeting the insulin receptor and IRS1 for ubiquitin-dependent degradation, comprising a central mechanism controlling insulin signal strength in skeletal muscle. These findings define MG53 as a novel therapeutic target for treating metabolic disorders and associated cardiovascular complications.
Nature 01/2013; · 36.28 Impact Factor
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ABSTRACT: Recent studies show that ischaemic postconditioning (PostC), similar to the well-established ischaemic preconditioning (IPC), confers cardioprotection against ischaemia/reperfusion (IR) injury, and both IPC and PostC can activate the reperfusion injury salvage kinase (RISK) pathway and the survivor activating factor enhancement (SAFE) pathway. PostC is clinically more attractive because of its therapeutic application at the predictable onset of reperfusion. Our previous studies have demonstrated that MG53 is a primary component of the IPC machinery. Here, we investigated the potential role of MG53 in PostC-mediated myocardial protection and explored the underlying mechanism.
Using Langendorff perfusion, we investigated IR injury in wild-type (wt) and MG53-deficient (mg53(-/-)) mouse hearts with or without PostC. IR-induced myocardial damage was markedly exacerbated in mg53(-/-) hearts compared with wt controls. PostC protected wt hearts against IR-induced myocardial infarction, myocyte necrosis, and apoptosis, but failed to protect mg53(-/-) hearts. The loss of PostC protection in mg53(-/-) hearts was attributed to selectively impaired PostC-activated RISK signalling. Mechanistically, MG53 is required for the interaction between caveolin 3 (CaV3) and the p85 subunit of phosphoinositide 3-kinase (p85-PI3K) and PostC-mediated activation of the RISK pathway. Importantly, a structure-function study revealed that the MG53 tripartite motif (TRIM) domain (aa1-284) physically interacted with CaV3 but not p85-PI3K, whereas the MG53 SPRY domain (aa285-477) interacted with p85-PI3K but not CaV3, indicating that MG53 binds to CaV3 and p85 at its N- and C-terminus, respectively.
We conclude that MG53 participates in PostC-mediated cardioprotection largely through tethering CaV3 and PI3K and subsequent activation of the RISK pathway.
Cardiovascular research 02/2011; 91(1):108-15. · 5.80 Impact Factor
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Chun-Mei Cao,
Yan Zhang,
Noah Weisleder,
Christopher Ferrante,
Xianhua Wang,
Fengxiang Lv,
Yi Zhang, Ruisheng Song,
Moonsun Hwang,
Li Jin,
Jiaojiao Guo,
Wei Peng,
Geng Li,
Miyuki Nishi,
Hiroshi Takeshima,
Jianjie Ma,
Rui-Ping Xiao
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ABSTRACT: Ischemic heart disease is the greatest cause of death in Western countries. The deleterious effects of cardiac ischemia are ameliorated by ischemic preconditioning (IPC), in which transient ischemia protects against subsequent severe ischemia/reperfusion injury. IPC activates multiple signaling pathways, including the reperfusion injury salvage kinase pathway (mainly PI3K-Akt-glycogen synthase kinase-3beta [GSK3beta] and ERK1/2) and the survivor activating factor enhancement pathway involving activation of the JAK-STAT3 axis. Nevertheless, the fundamental mechanism underlying IPC is poorly understood.
In the present study, we define MG53, a muscle-specific TRIM-family protein, as a crucial component of cardiac IPC machinery. Ischemia/reperfusion or hypoxia/oxidative stress applied to perfused mouse hearts or neonatal rat cardiomyocytes, respectively, causes downregulation of MG53, and IPC can prevent ischemia/reperfusion-induced decrease in MG53 expression. MG53 deficiency increases myocardial vulnerability to ischemia/reperfusion injury and abolishes IPC protection. Overexpression of MG53 attenuates whereas knockdown of MG53 enhances hypoxia- and H(2)O(2)-induced cardiomyocyte death. The cardiac protective effects of MG53 are attributable to MG53-dependent interaction of caveolin-3 with phosphatidylinositol 3 kinase and subsequent activation of the reperfusion injury salvage kinase pathway without altering the survivor activating factor enhancement pathway.
These results establish MG53 as a primary component of the cardiac IPC response, thus identifying a potentially important novel therapeutic target for the treatment of ischemic heart disease.
Circulation 06/2010; 121(23):2565-74. · 14.74 Impact Factor
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Gang Wang,
Xiaojun Zhu,
Wenjun Xie,
Peidong Han,
Kaitao Li,
Zhongcui Sun,
Yanru Wang,
Chunlei Chen, Ruisheng Song,
Chunmei Cao,
Jifeng Zhang,
Caihong Wu,
Jie Liu,
Heping Cheng
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ABSTRACT: Rad (Ras associated with diabetes) GTPase, a monomeric small G protein, binds to Ca(v)beta subunit of the L-type Ca(2+) channel (LCC) and thereby regulates LCC trafficking and activity. Emerging evidence suggests that Rad is an important player in cardiac arrhythmogenesis and hypertrophic remodeling. However, whether and how Rad involves in the regulation of excitation-contraction (EC) coupling is unknown.
This study aimed to investigate possible role of Rad in cardiac EC coupling and beta-adrenergic receptor (betaAR) inotropic mechanism.
Adenoviral overexpression of Rad by 3-fold in rat cardiomyocytes suppressed LCC current (I(Ca)), [Ca(2+)](i) transients, and contractility by 60%, 42%, and 38%, respectively, whereas the "gain" function of EC coupling was significantly increased, due perhaps to reduced "redundancy" of LCC in triggering sarcoplasmic reticulum release. Conversely, approximately 70% Rad knockdown by RNA interference increased I(Ca) (50%), [Ca(2+)](i) transients (52%) and contractility (58%) without altering EC coupling efficiency; and the dominant negative mutant RadS105N exerted a similar effect on I(Ca). Rad upregulation caused depolarizing shift of LCC activation and hastened time-dependent LCC inactivation; Rad downregulation, however, failed to alter these attributes. The Na(+)/Ca(2+) exchange activity, sarcoplasmic reticulum Ca(2+) content, properties of Ca(2+) sparks and propensity for Ca(2+) waves all remained unperturbed regardless of Rad manipulation. Rad overexpression, but not knockdown, negated betaAR effects on I(Ca) and Ca(2+) transients.
These results establish Rad as a novel endogenous regulator of cardiac EC coupling and betaAR signaling and support a parsimonious model in which Rad buffers Ca(v)beta to modulate LCC activity, EC coupling, and betaAR responsiveness.
Circulation Research 11/2009; 106(2):317-27. · 9.49 Impact Factor
