Identification of the amino acids 300-600 of IRS-2 as 14-3-3 binding region with the importance of IGF-1/insulin-regulated phosphorylation of Ser-573.
    
    
        
    
    
        
        PLoS ONE 7:e43296 (2012)
    
    
    
      
      
	
	    Phosphorylation of insulin receptor substrate (IRS)-2 on tyrosine residues is a key event in IGF-1/insulin signaling and leads to activation of the PI 3-kinase and the Ras/MAPK pathway. Furthermore, phosphorylated serine/threonine residues on IRS-2 can induce 14-3-3 binding. In this study we searched IRS-2 for novel phosphorylation sites and investigated the interaction between IRS-2 and 14-3-3. Mass spectrometry identified a total of 24 serine/threonine residues on IRS-2 with 12 sites unique for IRS-2 while the other residues are conserved in IRS-1 and IRS-2. IGF-1 stimulation led to increased binding of 14-3-3 to IRS-2 in transfected HEK293 cells and this binding was prevented by inhibition of the PI 3-kinase pathway and an Akt/PKB inhibitor. Insulin-stimulated interaction between endogenous IRS-2 and 14-3-3 was observed in rat hepatoma cells and in mice liver after an acute insulin stimulus and refeeding. Using different IRS-2 fragments enabled localization of the IGF-1-dependent 14-3-3 binding region spanning amino acids 300-600. The 24 identified residues on IRS-2 included several 14-3-3 binding candidates in the region 300-600. Single alanine mutants of these candidates led to the identification of serine 573 as 14-3-3 binding site. A phospho-site specific antibody was generated to further characterize serine 573. IGF-1-dependent phosphorylation of serine 573 was reduced by inhibition of PI 3-kinase and Akt/PKB. A negative role of this phosphorylation site was implicated by the alanine mutant of serine 573 which led to enhanced phosphorylation of Akt/PKB in an IGF-1 time course experiment. To conclude, our data suggest a physiologically relevant role for IGF-1/insulin-dependent 14-3-3 binding to IRS-2 involving serine 573.
	
	
	    
	
       
      
	
	    
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        Publication type
        Article: Journal article
    
 
    
        Document type
        Scientific Article
    
 
    
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        Keywords
        INSULIN-RECEPTOR SUBSTRATE-1; SKELETAL-MUSCLE CELLS; CRYSTAL-STRUCTURE; STRUCTURAL BASIS; PROTEIN-BINDING; IN-VIVO; RESISTANCE; ALPHA; DOMAIN; SITES
    
 
    
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        Language
        english
    
 
    
        Publication Year
        2012
    
 
    
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        HGF-reported in Year
        2012
    
 
    
    
        ISSN (print) / ISBN
        1932-6203
    
 
    
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	    Volume: 7,  
	    Issue: 8,  
	    Pages: ,  
	    Article Number: e43296 
	    Supplement: ,  
	
    
 
    
        
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            Publisher
            Public Library of Science (PLoS)
        
 
        
            Publishing Place
            Lawrence, Kan.
        
 
	
        
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        Reviewing status
        Peer reviewed
    
 
     
    
        POF-Topic(s)
        90000 - German Center for Diabetes Research
    
 
    
        Research field(s)
        Helmholtz Diabetes Center
    
 
    
        PSP Element(s)
        G-502400-001
G-502400-002
    
 
    
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        Erfassungsdatum
        2012-10-26