| Structural highlights
Disease
[AKT2_HUMAN] Note=Defects in AKT2 are a cause of susceptibility to breast cancer (BC). AKT2 promotes metastasis of tumor cells without affecting the latency of tumor development. With AKT3, plays also a pivotal role in the biology of glioblastoma. Defects in AKT2 are a cause of non-insulin-dependent diabetes mellitus (NIDDM) [MIM:125853]; also known as diabetes mellitus type 2 or maturity-onset diabetes. NIDDM is characterized by an autosomal dominant mode of inheritance, onset during adulthood and insulin resistance.[1] [2] Defects in AKT2 are a cause of hypoinsulinemic hypoglycemia with hemihypertrophy (HIHGHH) [MIM:240900]. HIHGHH is a disorder characterized by hypoglycemia, low insulin levels, low serum levels of ketone bodies and branched-chain amino acids, left-sided hemihypertrophy, neonatal macrosomia, reduced consciousness and hypoglycemic seizures.[3]
Function
[AKT2_HUMAN] AKT2 is one of 3 closely related serine/threonine-protein kinases (AKT1, AKT2 and AKT3) called the AKT kinase, and which regulate many processes including metabolism, proliferation, cell survival, growth and angiogenesis. This is mediated through serine and/or threonine phosphorylation of a range of downstream substrates. Over 100 substrate candidates have been reported so far, but for most of them, no isoform specificity has been reported. AKT is responsible of the regulation of glucose uptake by mediating insulin-induced translocation of the SLC2A4/GLUT4 glucose transporter to the cell surface. Phosphorylation of PTPN1 at 'Ser-50' negatively modulates its phosphatase activity preventing dephosphorylation of the insulin receptor and the attenuation of insulin signaling. Phosphorylation of TBC1D4 triggers the binding of this effector to inhibitory 14-3-3 proteins, which is required for insulin-stimulated glucose transport. AKT regulates also the storage of glucose in the form of glycogen by phosphorylating GSK3A at 'Ser-21' and GSK3B at 'Ser-9', resulting in inhibition of its kinase activity. Phosphorylation of GSK3 isoforms by AKT is also thought to be one mechanism by which cell proliferation is driven. AKT regulates also cell survival via the phosphorylation of MAP3K5 (apoptosis signal-related kinase). Phosphorylation of 'Ser-83' decreases MAP3K5 kinase activity stimulated by oxidative stress and thereby prevents apoptosis. AKT mediates insulin-stimulated protein synthesis by phosphorylating TSC2 at 'Ser-939' and 'Thr-1462', thereby activating mTORC1 signaling and leading to both phosphorylation of 4E-BP1 and in activation of RPS6KB1. AKT is involved in the phosphorylation of members of the FOXO factors (Forkhead family of transcription factors), leading to binding of 14-3-3 proteins and cytoplasmic localization. In particular, FOXO1 is phosphorylated at 'Thr-24', 'Ser-256' and 'Ser-319'. FOXO3 and FOXO4 are phosphorylated on equivalent sites. AKT has an important role in the regulation of NF-kappa-B-dependent gene transcription and positively regulates the activity of CREB1 (cyclic AMP (cAMP)-response element binding protein). The phosphorylation of CREB1 induces the binding of accessory proteins that are necessary for the transcription of pro-survival genes such as BCL2 and MCL1. AKT phosphorylates 'Ser-454' on ATP citrate lyase (ACLY), thereby potentially regulating ACLY activity and fatty acid synthesis. Activates the 3B isoform of cyclic nucleotide phosphodiesterase (PDE3B) via phosphorylation of 'Ser-273', resulting in reduced cyclic AMP levels and inhibition of lipolysis. Phosphorylates PIKFYVE on 'Ser-318', which results in increased PI(3)P-5 activity. The Rho GTPase-activating protein DLC1 is another substrate and its phosphorylation is implicated in the regulation cell proliferation and cell growth. AKT plays a role as key modulator of the AKT-mTOR signaling pathway controlling the tempo of the process of newborn neurons integration during adult neurogenesis, including correct neuron positioning, dendritic development and synapse formation. Signals downstream of phosphatidylinositol 3-kinase (PI(3)K) to mediate the effects of various growth factors such as platelet-derived growth factor (PDGF), epidermal growth factor (EGF), insulin and insulin-like growth factor I (IGF-I). AKT mediates the antiapoptotic effects of IGF-I. Essential for the SPATA13-mediated regulation of cell migration and adhesion assembly and disassembly. May be involved in the regulation of the placental development.[4] One of the few specific substrates of AKT2 identified recently is PITX2. Phosphorylation of PITX2 impairs its association with the CCND1 mRNA-stabilizing complex thus shortening the half-life of CCND1. AKT2 seems also to be the principal isoform responsible of the regulation of glucose uptake. Phosphorylates C2CD5 on 'Ser-197' during insulin-stimulated adipocytes. AKT2 is also specifically involved in skeletal muscle differentiation. Down-regulation by RNA interference reduces the expression of the phosphorylated form of BAD, resulting in the induction of caspase-dependent apoptosis. Phosphorylates CLK2 on 'Thr-343'.[5] [GSK3B_HUMAN] Constitutively active protein kinase that acts as a negative regulator in the hormonal control of glucose homeostasis, Wnt signaling and regulation of transcription factors and microtubules, by phosphorylating and inactivating glycogen synthase (GYS1 or GYS2), EIF2B, CTNNB1/beta-catenin, APC, AXIN1, DPYSL2/CRMP2, JUN, NFATC1/NFATC, MAPT/TAU and MACF1. Requires primed phosphorylation of the majority of its substrates. In skeletal muscle, contributes to insulin regulation of glycogen synthesis by phosphorylating and inhibiting GYS1 activity and hence glycogen synthesis. May also mediate the development of insulin resistance by regulating activation of transcription factors. Regulates protein synthesis by controlling the activity of initiation factor 2B (EIF2BE/EIF2B5) in the same manner as glycogen synthase. In Wnt signaling, GSK3B forms a multimeric complex with APC, AXIN1 and CTNNB1/beta-catenin and phosphorylates the N-terminus of CTNNB1 leading to its degradation mediated by ubiquitin/proteasomes. Phosphorylates JUN at sites proximal to its DNA-binding domain, thereby reducing its affinity for DNA. Phosphorylates NFATC1/NFATC on conserved serine residues promoting NFATC1/NFATC nuclear export, shutting off NFATC1/NFATC gene regulation, and thereby opposing the action of calcineurin. Phosphorylates MAPT/TAU on 'Thr-548', decreasing significantly MAPT/TAU ability to bind and stabilize microtubules. MAPT/TAU is the principal component of neurofibrillary tangles in Alzheimer disease. Plays an important role in ERBB2-dependent stabilization of microtubules at the cell cortex. Phosphorylates MACF1, inhibiting its binding to microtubules which is critical for its role in bulge stem cell migration and skin wound repair. Probably regulates NF-kappa-B (NFKB1) at the transcriptional level and is required for the NF-kappa-B-mediated anti-apoptotic response to TNF-alpha (TNF/TNFA). Negatively regulates replication in pancreatic beta-cells, resulting in apoptosis, loss of beta-cells and diabetes. Phosphorylates MUC1 in breast cancer cells, decreasing the interaction of MUC1 with CTNNB1/beta-catenin. Is necessary for the establishment of neuronal polarity and axon outgrowth. Phosphorylates MARK2, leading to inhibit its activity. Phosphorylates SIK1 at 'Thr-182', leading to sustain its activity. Phosphorylates ZC3HAV1 which enhances its antiviral activity. Phosphorylates SFPQ at 'Thr-687' upon T-cell activation.[6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
The protein kinase Akt/PKB is stimulated by the phosphorylation of two regulatory residues, Thr 309 of the activation segment and Ser 474 of the hydrophobic motif (HM), that are structurally and functionally conserved within the AGC kinase family. To understand the mechanism of PKB regulation, we determined the crystal structures of activated kinase domains of PKB in complex with a GSK3beta-peptide substrate and an ATP analog. The activated state of the kinase was generated by phosphorylating Thr 309 using PDK1 and mimicking Ser 474 phosphorylation either with the S474D substitution or by replacing the HM of PKB with that of PIFtide, a potent mimic of a phosphorylated HM. Comparison with the inactive PKB structure indicates that the role of Ser 474 phosphorylation is to promote the engagement of the HM with the N-lobe of the kinase domain, promoting a disorder-to-order transition of the alphaC helix. The alphaC helix, by interacting with pThr 309, restructures and orders the activation segment, generating an active kinase conformation. Analysis of the interactions between PKB and the GSK3beta-peptide explains how PKB selects for protein substrates distinct from those of PKA.
Crystal structure of an activated Akt/protein kinase B ternary complex with GSK3-peptide and AMP-PNP.,Yang J, Cron P, Good VM, Thompson V, Hemmings BA, Barford D Nat Struct Biol. 2002 Dec;9(12):940-4. PMID:12434148[18]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ George S, Rochford JJ, Wolfrum C, Gray SL, Schinner S, Wilson JC, Soos MA, Murgatroyd PR, Williams RM, Acerini CL, Dunger DB, Barford D, Umpleby AM, Wareham NJ, Davies HA, Schafer AJ, Stoffel M, O'Rahilly S, Barroso I. A family with severe insulin resistance and diabetes due to a mutation in AKT2. Science. 2004 May 28;304(5675):1325-8. PMID:15166380 doi:10.1126/science.1096706
- ↑ Semple RK, Sleigh A, Murgatroyd PR, Adams CA, Bluck L, Jackson S, Vottero A, Kanabar D, Charlton-Menys V, Durrington P, Soos MA, Carpenter TA, Lomas DJ, Cochran EK, Gorden P, O'Rahilly S, Savage DB. Postreceptor insulin resistance contributes to human dyslipidemia and hepatic steatosis. J Clin Invest. 2009 Feb;119(2):315-22. doi: 10.1172/JCI37432. Epub 2009 Jan 26. PMID:19164855 doi:10.1172/JCI37432
- ↑ Hussain K, Challis B, Rocha N, Payne F, Minic M, Thompson A, Daly A, Scott C, Harris J, Smillie BJ, Savage DB, Ramaswami U, De Lonlay P, O'Rahilly S, Barroso I, Semple RK. An activating mutation of AKT2 and human hypoglycemia. Science. 2011 Oct 28;334(6055):474. doi: 10.1126/science.1210878. Epub 2011 Oct, 6. PMID:21979934 doi:10.1126/science.1210878
- ↑ Heron-Milhavet L, Mamaeva D, Rochat A, Lamb NJ, Fernandez A. Akt2 is implicated in skeletal muscle differentiation and specifically binds Prohibitin2/REA. J Cell Physiol. 2008 Jan;214(1):158-65. PMID:17565718 doi:10.1002/jcp.21177
- ↑ Heron-Milhavet L, Mamaeva D, Rochat A, Lamb NJ, Fernandez A. Akt2 is implicated in skeletal muscle differentiation and specifically binds Prohibitin2/REA. J Cell Physiol. 2008 Jan;214(1):158-65. PMID:17565718 doi:10.1002/jcp.21177
- ↑ Boyle WJ, Smeal T, Defize LH, Angel P, Woodgett JR, Karin M, Hunter T. Activation of protein kinase C decreases phosphorylation of c-Jun at sites that negatively regulate its DNA-binding activity. Cell. 1991 Feb 8;64(3):573-84. PMID:1846781
- ↑ Welsh GI, Proud CG. Glycogen synthase kinase-3 is rapidly inactivated in response to insulin and phosphorylates eukaryotic initiation factor eIF-2B. Biochem J. 1993 Sep 15;294 ( Pt 3):625-9. PMID:8397507
- ↑ Beals CR, Sheridan CM, Turck CW, Gardner P, Crabtree GR. Nuclear export of NF-ATc enhanced by glycogen synthase kinase-3. Science. 1997 Mar 28;275(5308):1930-4. PMID:9072970
- ↑ Li Y, Bharti A, Chen D, Gong J, Kufe D. Interaction of glycogen synthase kinase 3beta with the DF3/MUC1 carcinoma-associated antigen and beta-catenin. Mol Cell Biol. 1998 Dec;18(12):7216-24. PMID:9819408
- ↑ Frame S, Cohen P, Biondi RM. A common phosphate binding site explains the unique substrate specificity of GSK3 and its inactivation by phosphorylation. Mol Cell. 2001 Jun;7(6):1321-7. PMID:11430833
- ↑ Cho JH, Johnson GV. Primed phosphorylation of tau at Thr231 by glycogen synthase kinase 3beta (GSK3beta) plays a critical role in regulating tau's ability to bind and stabilize microtubules. J Neurochem. 2004 Jan;88(2):349-58. PMID:14690523
- ↑ Zhou BP, Deng J, Xia W, Xu J, Li YM, Gunduz M, Hung MC. Dual regulation of Snail by GSK-3beta-mediated phosphorylation in control of epithelial-mesenchymal transition. Nat Cell Biol. 2004 Oct;6(10):931-40. Epub 2004 Sep 26. PMID:15448698 doi:10.1038/ncb1173
- ↑ Hashimoto YK, Satoh T, Okamoto M, Takemori H. Importance of autophosphorylation at Ser186 in the A-loop of salt inducible kinase 1 for its sustained kinase activity. J Cell Biochem. 2008 Aug 1;104(5):1724-39. doi: 10.1002/jcb.21737. PMID:18348280 doi:10.1002/jcb.21737
- ↑ Heyd F, Lynch KW. Phosphorylation-dependent regulation of PSF by GSK3 controls CD45 alternative splicing. Mol Cell. 2010 Oct 8;40(1):126-37. doi: 10.1016/j.molcel.2010.09.013. PMID:20932480 doi:10.1016/j.molcel.2010.09.013
- ↑ Zaoui K, Benseddik K, Daou P, Salaun D, Badache A. ErbB2 receptor controls microtubule capture by recruiting ACF7 to the plasma membrane of migrating cells. Proc Natl Acad Sci U S A. 2010 Oct 26;107(43):18517-22. doi:, 10.1073/pnas.1000975107. Epub 2010 Oct 11. PMID:20937854 doi:10.1073/pnas.1000975107
- ↑ Sun L, Lv F, Guo X, Gao G. Glycogen synthase kinase 3beta (GSK3beta) modulates antiviral activity of zinc-finger antiviral protein (ZAP). J Biol Chem. 2012 Jun 29;287(27):22882-8. doi: 10.1074/jbc.M111.306373. Epub 2012, Apr 18. PMID:22514281 doi:10.1074/jbc.M111.306373
- ↑ Dajani R, Fraser E, Roe SM, Yeo M, Good VM, Thompson V, Dale TC, Pearl LH. Structural basis for recruitment of glycogen synthase kinase 3beta to the axin-APC scaffold complex. EMBO J. 2003 Feb 3;22(3):494-501. PMID:12554650 doi:10.1093/emboj/cdg068
- ↑ Yang J, Cron P, Good VM, Thompson V, Hemmings BA, Barford D. Crystal structure of an activated Akt/protein kinase B ternary complex with GSK3-peptide and AMP-PNP. Nat Struct Biol. 2002 Dec;9(12):940-4. PMID:12434148 doi:10.1038/nsb870
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