The E3 ligase TTC3 facilitates ubiquitination and degradation of phosphorylated Akt.

The serine threonine kinase Akt is a core survival factor that underlies a variety of human diseases. Although regulatory phosphorylation and dephosphorylation have been well documented, the other posttranslational mechanisms that modulate Akt activity remain unclear. We show here that tetratricopeptide repeat domain 3 (TTC3) is an E3 ligase that interacts with Akt. TTC3 contains a canonical RING finger motif, a pair of tetratricopeptide motifs, a putative Akt phosphorylation site, and nuclear localization signals, and is encoded by a gene within the Down syndrome (DS) critical region on chromosome 21. TTC3 is an Akt-specific E3 ligase that binds to phosphorylated Akt and facilitates its ubiquitination and degradation within the nucleus. Moreover, DS cells exhibit elevated TTC3 expression, reduced phosphorylated Akt, and accumulation in the G(2)M phase, which can be reversed by TTC3 siRNA or Myr-Akt. Thus, interaction between TTC3 and Akt may contribute to the clinical symptoms of DS.

[1]  M. Birnbaum,et al.  Expression of a Constitutively Active Akt Ser/Thr Kinase in 3T3-L1 Adipocytes Stimulates Glucose Uptake and Glucose Transporter 4 Translocation* , 1996, The Journal of Biological Chemistry.

[2]  M. Oshimura,et al.  Mice containing a human chromosome 21 model behavioral impairment and cardiac anomalies of Down's syndrome. , 2001, Human molecular genetics.

[3]  J. Delabar,et al.  Regional and cellular specificity of the expression of TPRD, the tetratricopeptide Down syndrome gene, during human embryonic development , 2000, Mechanisms of Development.

[4]  C. Roumestand,et al.  Proto‐oncogene TCL1: more than just a coactivator for Akt , 2007, FASEB journal : official publication of the Federation of American Societies for Experimental Biology.

[5]  Sandya Liyanarachchi,et al.  Acute myeloid leukemia with complex karyotypes and abnormal chromosome 21: Amplification discloses overexpression of APP, ETS2, and ERG genes. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[6]  J. Richtsmeier,et al.  Too much of a good thing: mechanisms of gene action in Down syndrome. , 2001, Trends in genetics : TIG.

[7]  Stylianos E. Antonarakis,et al.  Chromosome 21 and Down syndrome: from genomics to pathophysiology , 2004, Nature Reviews Genetics.

[8]  M. Hochstrasser,et al.  Evolution and function of ubiquitin-like protein-conjugation systems , 2000, Nature Cell Biology.

[9]  J. Laine,et al.  The protooncogene TCL1 is an Akt kinase coactivator. , 2000, Molecular cell.

[10]  L. Petrucelli,et al.  Akt and CHIP coregulate tau degradation through coordinated interactions , 2008, Proceedings of the National Academy of Sciences.

[11]  M. Yaffe,et al.  A motif-based profile scanning approach for genome-wide prediction of signaling pathways , 2001, Nature Biotechnology.

[12]  Lewis C. Cantley,et al.  AKT/PKB Signaling: Navigating Downstream , 2007, Cell.

[13]  J. Frahm,et al.  Essential role of protein kinase Bγ (PKBγ/Akt3) in postnatal brain development but not in glucose homeostasis , 2005, Development.

[14]  P. Cohen,et al.  Role of Translocation in the Activation and Function of Protein Kinase B* , 1997, The Journal of Biological Chemistry.

[15]  T. Ludwig,et al.  Negative Regulation of AKT Activation by BRCA1. , 2008, Cancer research.

[16]  P. Hieter,et al.  Tetratrico peptide repeat interactions: to TPR or not to TPR? , 1995, Trends in biochemical sciences.

[17]  A. Levey,et al.  Interaction of Akt-phosphorylated SRPK2 with 14-3-3 Mediates Cell Cycle and Cell Death in Neurons* , 2009, The Journal of Biological Chemistry.

[18]  M. Noguchi,et al.  Identification of Nerve Growth Factor-responsive Element of the TCL1 Promoter as a Novel Negative Regulatory Element* , 2006, Journal of Biological Chemistry.

[19]  Satomi Kato,et al.  Differential activation of CREB by Akt1 and Akt2. , 2007, Biochemical and biophysical research communications.

[20]  Y. Hayashi,et al.  Establishment of a human leukaemic cell line (CMK) with megakaryocytic characteristics from a Down's syndrome patient with acute megakaryoblastic leukaemia , 1989, British journal of haematology.

[21]  Michael B. Yaffe,et al.  Scansite 2.0: proteome-wide prediction of cell signaling interactions using short sequence motifs , 2003, Nucleic Acids Res..

[22]  R. Deshaies,et al.  Multiubiquitin Chain Receptors Define a Layer of Substrate Selectivity in the Ubiquitin-Proteasome System , 2004, Cell.

[23]  T. Ludwig,et al.  Role for Akt3/Protein Kinase Bγ in Attainment of Normal Brain Size , 2005, Molecular and Cellular Biology.

[24]  B. Yankner,et al.  Apoptosis and increased generation of reactive oxygen species in Down's syndrome neurons in vitro , 1995, Nature.

[25]  N. Rosen,et al.  Akt Forms an Intracellular Complex with Heat Shock Protein 90 (Hsp90) and Cdc37 and Is Destabilized by Inhibitors of Hsp90 Function* , 2002, The Journal of Biological Chemistry.

[26]  A. Newton,et al.  The mammalian target of rapamycin complex 2 controls folding and stability of Akt and protein kinase C , 2008, The EMBO journal.

[27]  P. Pandolfi,et al.  Activation of Akt/Protein Kinase B Overcomes a G2/M Cell Cycle Checkpoint Induced by DNA Damage , 2002, Molecular and Cellular Biology.

[28]  T. Hunter The age of crosstalk: phosphorylation, ubiquitination, and beyond. , 2007, Molecular cell.

[29]  F. Di Cunto,et al.  The Down syndrome critical region protein TTC3 inhibits neuronal differentiation via RhoA and Citron kinase , 2007, Journal of Cell Science.

[30]  S. Fang,et al.  RING fingers mediate ubiquitin-conjugating enzyme (E2)-dependent ubiquitination. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[31]  R. Reeves,et al.  Global disruption of the cerebellar transcriptome in a Down syndrome mouse model. , 2003, Human molecular genetics.

[32]  K. Nakayama,et al.  Functional Regulation of FEZ1 by the U-box-type Ubiquitin Ligase E4B Contributes to Neuritogenesis* , 2004, Journal of Biological Chemistry.

[33]  Michael Chinkers,et al.  Overlapping Sites of Tetratricopeptide Repeat Protein Binding and Chaperone Activity in Heat Shock Protein 90* , 2000, The Journal of Biological Chemistry.

[34]  M. Hattori,et al.  Molecular characterization of the mouse mtprd gene, a homologue of human TPRD: unique gene expression suggesting its critical role in the pathophysiology of Down syndrome. , 1998, Journal of Biochemistry (Tokyo).

[35]  P. Cohen,et al.  Mechanism of activation of protein kinase B by insulin and IGF‐1. , 1996, The EMBO journal.

[36]  B. Hemmings,et al.  Advances in protein kinase B signalling: AKTion on multiple fronts. , 2004, Trends in biochemical sciences.

[37]  Jennifer Skeen,et al.  Dwarfism, impaired skin development, skeletal muscle atrophy, delayed bone development, and impeded adipogenesis in mice lacking Akt1 and Akt2. , 2003, Genes & development.

[38]  P. Tsichlis,et al.  Regulation of the Akt kinase by interacting proteins , 2005, Oncogene.

[39]  Min Gao,et al.  Regulating the regulators: control of protein ubiquitination and ubiquitin-like modifications by extracellular stimuli. , 2005, Molecular cell.

[40]  K. Nakayama,et al.  U Box Proteins as a New Family of Ubiquitin-Protein Ligases* , 2001, The Journal of Biological Chemistry.

[41]  C. Pickart,et al.  Ubiquitin: structures, functions, mechanisms. , 2004, Biochimica et biophysica acta.