title: 14-3-3beta binds to and negatively regulates the tuberous sclerosis complex 2 (TSC2) tumor suppressor gene product, tuberin.
abstract: TSC2, or tuberin, is the product of the tuberous sclerosis tumor suppressor gene TSC2 and acts downstream of the phosphatidylinositol 3-kinase-Akt signaling pathway to negatively regulate cellular growth. One mechanism underlying its function is to assemble into a heterodimer with the TSC1 gene product TSC1, or hamartin, resulting in a reduction in phosphorylation, and hence activation, of the ribosomal subunit S6 kinase (S6K). We identified a novel interaction between TSC2 and 14-3-3beta. We found that 14-3-3beta does not interfere with TSC1-TSC2 binding and can form a ternary complex with these two proteins. Association between 14-3-3beta and TSC2 requires phosphorylation of TSC2 at a unique residue that is not a known Akt phosphorylation site. The overexpression of 14-3-3beta compromises the ability of the TSC1-TSC2 complex to reduce S6K phosphorylation. The antagonistic activity of 14-3-3beta toward TSC is dependent on the 14-3-3beta-TSC2 interaction, since a mutant of TSC2 that is not recognized by 14-3-3beta is refractory to 14-3-3beta. We suggest that 14-3-3 proteins interact with the TSC1-TSC2 complex and negatively regulate the function of the TSC proteins.
authors.affiliation: Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics, Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, 27599-7295, USA.
authors.forename: Stuart D
authors.initials: SD
authors.lastname: Shumway
authors.forename: Yong
authors.initials: Y
authors.lastname: Li
authors.forename: Yue
authors.initials: Y
authors.lastname: Xiong
mesh_terms: D048948:14-3-3 Proteins; D001665:Binding Sites; D015153:Blotting, Western; D002460:Cell Line; D005786:Gene Expression Regulation; D016147:Genes, Tumor Suppressor; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D015398:Signal Transduction; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D020798:Two-Hybrid System Techniques; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
chemical_list: D048948:14-3-3 Proteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C000624650:TSC1 protein, human; C000624653:TSC2 protein, human; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; C482982:YWHAB protein, human; D014446:Tyrosine 3-Monooxygenase; D005982:Glutathione Transferase; D019893:Ribosomal Protein S6 Kinases