Document Detail

Activation of phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) signaling and the consequent induction of transformation by overexpressed 14-3-3γ protein require specific amino acids within 14-3-3γ N-terminal variable region II.
MedLine Citation:
PMID:  23115241     Owner:  NLM     Status:  MEDLINE    
Members of the 14-3-3 superfamily regulate numerous cellular functions by binding phosphoproteins. The seven human isoforms (and the myriad of other eukaryotic 14-3-3 proteins) are highly conserved in amino acid sequence and secondary structure, yet there is abundant evidence that the various isoforms manifest disparate as well as common functions. Several of the human 14-3-3 isoforms are dysregulated in certain cancers and thus have been implicated in oncogenesis; experimentally, 14-3-3γ behaves as an oncogene, whereas 14-3-3σ acts as a tumor suppressor. In this study, we sought to localize these opposing phenotypes to specific regions of the two isoforms and then to individual amino acids therein. Using a bioinformatics approach, six variable regions (VRI-VRVI) were identified. Using this information, two sets of constructs were created in which N-terminal portions (including either VRI-IV or only VRI and VRII) of 14-3-3γ and 14-3-3σ were swapped; NIH3T3 cells overexpressing the four chimeric proteins were tested for transformation activity (focus formation, growth in soft agar) and activation of PI3K and MAPK signaling. We found that the specific phenotypes of 14-3-3γ are associated with the N-terminal 40 amino acids (VRI and VRII); in like fashion, VRI and VRII of 14-3-3σ dictated its tumor suppressor function. Using individual amino acid substitutions within the 14-3-3γ VRII, we identified two residues required for and two contributing to the γ-specific phenotypes. Our observations suggest that isoform-specific phenotypes are dictated by a relatively few amino acids within variable regions.
Vijayababu M Radhakrishnan; Charles W Putnam; Jesse D Martinez
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2012-10-31
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  287     ISSN:  1083-351X     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2012-12-24     Completed Date:  2013-02-26     Revised Date:  2014-04-16    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  43300-11     Citation Subset:  IM    
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MeSH Terms
14-3-3 Proteins / biosynthesis*,  genetics
Amino Acid Substitution
Cell Transformation, Neoplastic / genetics,  metabolism*,  pathology
Extracellular Signal-Regulated MAP Kinases / genetics,  metabolism*
Gene Expression
MAP Kinase Signaling System*
Mutation, Missense
NIH 3T3 Cells
Oncogene Proteins / biosynthesis*,  genetics
Peptide Mapping
Phosphatidylinositol 3-Kinases / genetics,  metabolism*
Protein Structure, Tertiary
Recombinant Fusion Proteins / genetics,  metabolism
Grant Support
Reg. No./Substance:
0/14-3-3 Proteins; 0/Oncogene Proteins; 0/Recombinant Fusion Proteins; EC 2.7.1.-/Phosphatidylinositol 3-Kinases; EC Signal-Regulated MAP Kinases

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