title: MG53 participates in ischaemic postconditioning through the RISK signalling pathway.
abstract: OBJECTIVE
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  We conclude that MG53 participates in PostC-mediated cardioprotection largely through tethering CaV3 and PI3K and subsequent activation of the RISK pathway.
authors.affiliation: Institute of Molecular Medicine, Peking University, Beijing 100871, People's Republic of China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Fengxiang
authors.initials: F
authors.lastname: Lv
authors.forename: Li
authors.initials: L
authors.lastname: Jin
authors.forename: Wei
authors.initials: W
authors.lastname: Peng
authors.forename: Ruisheng
authors.initials: R
authors.lastname: Song
authors.forename: Jianjie
authors.initials: J
authors.lastname: Ma
authors.forename: Chun-Mei
authors.initials: CM
authors.lastname: Cao
authors.forename: Rui-Ping
authors.initials: RP
authors.lastname: Xiao
mesh_terms: D020816:Amino Acid Motifs; D000704:Analysis of Variance; D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D051244:Caveolin 3 / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D057809:HEK293 Cells; D006801:Humans; D057775:Ischemic Postconditioning; D008565:Membrane Proteins; D051379:Mice; D018345:Mice, Knockout; D009203:Myocardial Infarction / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D015428:Myocardial Reperfusion Injury / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D009336:Necrosis; D010477:Perfusion; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D025941:Protein Interaction Mapping; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection
chemical_list: D002352:Carrier Proteins; C495548:Cav3 protein, mouse; D051244:Caveolin 3; C538824:MG53 protein, mouse; D008565:Membrane Proteins; D021122:Protein Subunits; D011494:Protein Kinases; D058539:Phosphatidylinositol 3-Kinase