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Morris J. Birnbaum - One of the best experts on this subject based on the ideXlab platform.

  • AKT1 and akt2 maintain hematopoietic stem cell function by regulating reactive oxygen species
    Blood, 2010
    Co-Authors: Marisa M Juntilla, Morris J. Birnbaum, Marco Calamito, Vineet Patil, Rohan P Joshi, Gary A Koretzky
    Abstract:

    Although AKT is essential for multiple cellular functions, the role of this kinase family in hematopoietic stem cells (HSCs) is unknown. Thus, we analyzed HSC function in mice deficient in the 2 isoforms most highly expressed in the hematopoietic compartment, AKT1 and AKT2. Although loss of either isoform had only a minimal effect on HSC function, AKT1/2 double-deficient HSCs competed poorly against wild-type cells in the development of myeloid and lymphoid cells in in vivo reconstitution assays. Serial transplantations revealed an essential role for AKT1 and AKT2 in the maintenance of long-term HSCs (LT-HSCs). AKT1/2 double-deficient LT-HSCs were found to persist in the G0 phase of the cell cycle, suggesting that the long-term functional defects are caused by increased quiescence. Furthermore, we found that the intracellular content of reactive oxygen species (ROS) is dependent on AKT because double-deficient HSCs demonstrate decreased ROS. The importance of maintaining ROS for HSC differentiation was shown by a rescue of the differentiation defect after pharmacologically increasing ROS levels in double-deficient HSCs. These data implicate AKT1 and AKT2 as critical regulators of LT-HSC function and suggest that defective ROS homeostasis may contribute to failed hematopoiesis.

  • AKT1 and Akt2 promote peripheral B-cell maturation and survival.
    Blood, 2009
    Co-Authors: Marco Calamito, Marisa M Juntilla, Gary A Koretzky, Jeffrey C Rathmell, Morris J. Birnbaum, Matthew B. Thomas, Daniel L. Northrup, David Allman
    Abstract:

    Although the 3 isoforms of Akt regulate cell growth, proliferation, and survival in a wide variety of cell types, their role in B-cell development is unknown. We assessed B-cell maturation in the bone marrow (BM) and periphery in chimeras established with fetal liver progenitors lacking AKT1 and/or Akt2. We found that the generation of marginal zone (MZ) and B1 B cells, 2 key sources of antibacterial antibodies, was highly dependent on the combined expression of AKT1 and Akt2. In contrast, AKT1/2 deficiency did not negatively affect the generation of transitional or mature follicular B cells in the periphery or their precursors in the BM. However, AKT1/2-deficient follicular B cells exhibited a profound survival defect when forced to compete against wild-type B cells in vivo. Altogether, these studies show that Akt signaling plays a key role in peripheral B-cell maturation and survival.

  • akt2 and sgk3 are both determinants of postnatal hair follicle development
    The FASEB Journal, 2009
    Co-Authors: Theodora M Mauro, Morris J. Birnbaum, James A Mccormick, Jing Wang, Krishna M Boini, Leena Ray, Bobby R Monks, Florian Lang, David A Pearce
    Abstract:

    SGK3, which previously has been shown to play a key role in hair follicle development in mice, is a member of the AGC family of serine-threonine kinases. Mice lacking SGK3 have abnormal follicle cycling, which begins shortly after birth and ameliorates substantially with age. However, this developmental abnormality is not recapitulated in mice lacking closely related kinases AKT1, Akt2, or Akt3. To examine whether Akt2 interacts with SGK3 in postnatal hair development, we have generated and characterized Akt2/SGK3 double knockouts (DKOs). We find that the DKO mice have a defect in hair growth that is markedly worse than that of SGK3(-/-) mice and does not ameliorate with age. Morphologically, this defect is characterized by accelerated entry into catagen and through anagen, irregular hair follicle orientation, and increased expression of sebaceous glands. The defect is preceded by a profound failure to increase follicle matrix cell nuclear beta-catenin accumulation and proliferation at the onset of morphogenesis. Furthermore, in cultured keratinocytes, transfected Akt2 and SGK3 both stimulate transcription of a beta-catenin-LEF1-dependent reporter gene. Thus, SGK3 and Akt2 both appear to play important roles in postnatal hair follicle morphogenesis, likely because of their redundant regulation of beta-catenin-dependent transcriptional processes, which control hair follicle cell proliferation.

  • AKT1 and akt2 are required for αβ thymocyte survival and differentiation
    Proceedings of the National Academy of Sciences of the United States of America, 2007
    Co-Authors: Marisa M Juntilla, Jessica A Wofford, Jeffrey C Rathmell, Morris J. Birnbaum, Gary A Koretzky
    Abstract:

    The β-selection checkpoint in αβT lymphocyte development occurs at the double negative (DN) 3 (CD4−CD8−CD25+c-kit−) stage, when further differentiation requires a signal from the newly rearranged TCR β chain. Thymocytes with mutations in key signaling molecules in the phosphatidylinositol 3-kinase–Akt pathway manifest defects in survival, proliferation, and differentiation past the β-selection checkpoint. However, little information is available regarding the role of Akt itself in thymocyte development. In this study, we explore the role of the two Akt isoforms most highly expressed in the thymus, AKT1 and Akt2, in early T cell development. Using several complementary approaches, we find that deletion of AKT1 results in only minor defects in thymocyte development. The AKT1−/−Akt2−/− thymocytes manifest a severe developmental block at the DN3 stage and ultimately fail to repopulate the T cell compartment of an irradiated host. Further, we show that AKT1−/−Akt2−/− DN3 cells have decreased glucose uptake and die in response to TCR stimulation in vitro. Study of thymocytes from the genetically altered mice suggests that the cause of the developmental defect is due to apoptosis, partially caused by decreased cellular growth and metabolism at the DN3 stage. Our results show that Akt protects thymocytes from cell death during the β-selection checkpoint.

  • opposing roles for AKT1 and akt2 in rac pak signaling and cell migration
    Journal of Biological Chemistry, 2006
    Co-Authors: Guo-lei Zhou, Morris J. Birnbaum, Sun Sik Bae, Kanav Bhatheja, David F. Tucker, Jeffrey Field
    Abstract:

    The Akt/PKB isoforms have different roles in animals, with Akt2 primarily regulating metabolic signaling and AKT1 regulating growth and survival. Here we show distinct roles for AKT1 and Akt2 in mouse embryo fibroblast cell migration and regulation of the cytoskeleton. AKT1-deficient cells responded poorly to platelet-derived growth factor while Akt2-deficient cells had a dramatically enhanced response, resulting in a substantial increase in dorsal ruffling. Swapping domains between AKT1 and Akt2 demonstrated that the N-terminal region containing the pleckstrin homology domain and a linker region distinguishes the two isoforms, while the catalytic domains are interchangeable. Akt2 knock-out cells also migrated faster than wild-type cells, especially through extracellular matrix (ECM), while AKT1 knock-out cells migrated more slowly than wild-type cells. Consistently, Akt2 knock-out cells had elevated Pak1 and Rac activities, suggesting that Akt2 inhibits Rac and Pak1. Both Akt2 and AKT1 associated in complexes with Pak1, but only Akt2 inhibited Pak1 in kinase assays, suggesting an underlying molecular basis for the different cellular phenotypes. Together these data provide evidence for an unexpected functional link between Akt2 and Pak1 that opposes the actions of AKT1 on cell migration.

Manfred Jucker - One of the best experts on this subject based on the ideXlab platform.

  • akt3 regulates erbb2 erbb3 and estrogen receptor α expression and contributes to endocrine therapy resistance of erbb2 breast tumor cells from balb neut mice
    Cellular Signalling, 2014
    Co-Authors: Nicole Grabinski, Katharina Mollmann, Karin Mildelangosch, Volkmar Muller, Udo Schumacher, Burkhard Brandt, Klaus Pantel, Manfred Jucker
    Abstract:

    Abstract ErbB2+ breast cancer is an aggressive breast cancer subtype generally associated with lower estrogen receptor alpha (ERα) expression and more aggressive tumor behavior compared to ERα+/ErbB2− breast cancer. The ErbB2+ phenotype is associated with resistance to endocrine therapy, e.g. the selective estrogen receptor modulator Tamoxifen. However, the mechanisms underlying endocrine resistance are not fully understood. Here, we investigated the impact of AKT signaling and distinct functional roles of AKT isoforms in ErbB2+ breast cancer from Balb-neuT mice. AKT isoform specific in vitro kinase assays revealed that AKT3 is activated in Balb-neuT breast tumors in comparison to normal murine breast tissue. Knock-down of AKT3, but not of AKT1 or AKT2, led to reduced expression and tyrosine-phosphorylation of ErbB2 and ErbB3 in Balb-neuT-derived mammary tumor cells. In contrast, expression of ERα was strongly up-regulated and phosphorylation of the AKT substrate Foxo3a which regulates ERα transcription was decreased in AKT3 knockdown cells. These data suggest that ERα expression is down regulated via AKT3/Foxo3a signaling in ErbB2+ breast cancer cells. Furthermore, up-regulation of ERα after depletion of AKT3 resulted in a significant increase in Tamoxifen responsiveness of Balb-neuT-derived mammary tumor cells. In addition, Tamoxifen resistant human breast cancer cell lines showed increased AKT3 expression and activity in comparison to Tamoxifen responsive MCF-7 cells. Finally, by AKT isoform specific in vitro kinase assays of human breast cancer samples, AKT3 activity was detected in ErbB2+ and triple negative tumors but not in ERα+ breast cancer. Our data indicate that AKT3 regulates the expression of ErbB2, ErbB3 and ERα and demonstrate that down-regulation of activated AKT3 can sensitize ErbB2+ breast cancer cells for treatment with Tamoxifen. Therefore, AKT3 targeting might be a new promising strategy for therapy of ErbB2+/ERα− breast cancer and might further increase the responsiveness to an endocrine therapy approach.

  • akt3 regulates erbb2 erbb3 and estrogen receptor α expression and contributes to endocrine therapy resistance of erbb2 breast tumor cells from balb neut mice
    Cellular Signalling, 2014
    Co-Authors: Nicole Grabinski, Katharina Mollmann, Karin Mildelangosch, Volkmar Muller, Udo Schumacher, Burkhard Brandt, Klaus Pantel, Manfred Jucker
    Abstract:

    ErbB2(+) breast cancer is an aggressive breast cancer subtype generally associated with lower estrogen receptor alpha (ERα) expression and more aggressive tumor behavior compared to ERα(+)/ErbB2(-) breast cancer. The ErbB2(+) phenotype is associated with resistance to endocrine therapy, e.g. the selective estrogen receptor modulator Tamoxifen. However, the mechanisms underlying endocrine resistance are not fully understood. Here, we investigated the impact of AKT signaling and distinct functional roles of AKT isoforms in ErbB2(+) breast cancer from Balb-neuT mice. AKT isoform specific in vitro kinase assays revealed that AKT3 is activated in Balb-neuT breast tumors in comparison to normal murine breast tissue. Knock-down of AKT3, but not of AKT1 or AKT2, led to reduced expression and tyrosine-phosphorylation of ErbB2 and ErbB3 in Balb-neuT-derived mammary tumor cells. In contrast, expression of ERα was strongly up-regulated and phosphorylation of the AKT substrate Foxo3a which regulates ERα transcription was decreased in AKT3 knockdown cells. These data suggest that ERα expression is down regulated via AKT3/Foxo3a signaling in ErbB2(+) breast cancer cells. Furthermore, up-regulation of ERα after depletion of AKT3 resulted in a significant increase in Tamoxifen responsiveness of Balb-neuT-derived mammary tumor cells. In addition, Tamoxifen resistant human breast cancer cell lines showed increased AKT3 expression and activity in comparison to Tamoxifen responsive MCF-7 cells. Finally, by AKT isoform specific in vitro kinase assays of human breast cancer samples, AKT3 activity was detected in ErbB2(+) and triple negative tumors but not in ERα(+) breast cancer. Our data indicate that AKT3 regulates the expression of ErbB2, ErbB3 and ERα and demonstrate that down-regulation of activated AKT3 can sensitize ErbB2(+) breast cancer cells for treatment with Tamoxifen. Therefore, AKT3 targeting might be a new promising strategy for therapy of ErbB2(+)/ERα(-) breast cancer and might further increase the responsiveness to an endocrine therapy approach.

Nicole Grabinski - One of the best experts on this subject based on the ideXlab platform.

  • downregulation of akt3 increases migration and metastasis in triple negative breast cancer cells by upregulating s100a4
    PLOS ONE, 2016
    Co-Authors: Astrid Grottke, Nicole Grabinski, Florian Ewald, Tobias Lange, Dominik Norz, Christiane Herzberger, Johanna Bach, Lareen Graser, Frank Hoppner, Bjorn Nashan
    Abstract:

    Background Treatment of breast cancer patients with distant metastases represents one of the biggest challenges in today’s gynecological oncology. Therefore, a better understanding of mechanisms promoting the development of metastases is of paramount importance. The serine/threonine kinase AKT was shown to drive cancer progression and metastasis. However, there is emerging data that single AKT isoforms (i.e. AKT1, AKT2 and AKT3) have different or even opposing functions in the regulation of cancer cell migration in vitro, giving rise to the hypothesis that inhibition of distinct AKT isoforms might have undesirable effects on cancer dissemination in vivo.

  • akt3 regulates erbb2 erbb3 and estrogen receptor α expression and contributes to endocrine therapy resistance of erbb2 breast tumor cells from balb neut mice
    Cellular Signalling, 2014
    Co-Authors: Nicole Grabinski, Katharina Mollmann, Karin Mildelangosch, Volkmar Muller, Udo Schumacher, Burkhard Brandt, Klaus Pantel, Manfred Jucker
    Abstract:

    Abstract ErbB2+ breast cancer is an aggressive breast cancer subtype generally associated with lower estrogen receptor alpha (ERα) expression and more aggressive tumor behavior compared to ERα+/ErbB2− breast cancer. The ErbB2+ phenotype is associated with resistance to endocrine therapy, e.g. the selective estrogen receptor modulator Tamoxifen. However, the mechanisms underlying endocrine resistance are not fully understood. Here, we investigated the impact of AKT signaling and distinct functional roles of AKT isoforms in ErbB2+ breast cancer from Balb-neuT mice. AKT isoform specific in vitro kinase assays revealed that AKT3 is activated in Balb-neuT breast tumors in comparison to normal murine breast tissue. Knock-down of AKT3, but not of AKT1 or AKT2, led to reduced expression and tyrosine-phosphorylation of ErbB2 and ErbB3 in Balb-neuT-derived mammary tumor cells. In contrast, expression of ERα was strongly up-regulated and phosphorylation of the AKT substrate Foxo3a which regulates ERα transcription was decreased in AKT3 knockdown cells. These data suggest that ERα expression is down regulated via AKT3/Foxo3a signaling in ErbB2+ breast cancer cells. Furthermore, up-regulation of ERα after depletion of AKT3 resulted in a significant increase in Tamoxifen responsiveness of Balb-neuT-derived mammary tumor cells. In addition, Tamoxifen resistant human breast cancer cell lines showed increased AKT3 expression and activity in comparison to Tamoxifen responsive MCF-7 cells. Finally, by AKT isoform specific in vitro kinase assays of human breast cancer samples, AKT3 activity was detected in ErbB2+ and triple negative tumors but not in ERα+ breast cancer. Our data indicate that AKT3 regulates the expression of ErbB2, ErbB3 and ERα and demonstrate that down-regulation of activated AKT3 can sensitize ErbB2+ breast cancer cells for treatment with Tamoxifen. Therefore, AKT3 targeting might be a new promising strategy for therapy of ErbB2+/ERα− breast cancer and might further increase the responsiveness to an endocrine therapy approach.

  • akt3 regulates erbb2 erbb3 and estrogen receptor α expression and contributes to endocrine therapy resistance of erbb2 breast tumor cells from balb neut mice
    Cellular Signalling, 2014
    Co-Authors: Nicole Grabinski, Katharina Mollmann, Karin Mildelangosch, Volkmar Muller, Udo Schumacher, Burkhard Brandt, Klaus Pantel, Manfred Jucker
    Abstract:

    ErbB2(+) breast cancer is an aggressive breast cancer subtype generally associated with lower estrogen receptor alpha (ERα) expression and more aggressive tumor behavior compared to ERα(+)/ErbB2(-) breast cancer. The ErbB2(+) phenotype is associated with resistance to endocrine therapy, e.g. the selective estrogen receptor modulator Tamoxifen. However, the mechanisms underlying endocrine resistance are not fully understood. Here, we investigated the impact of AKT signaling and distinct functional roles of AKT isoforms in ErbB2(+) breast cancer from Balb-neuT mice. AKT isoform specific in vitro kinase assays revealed that AKT3 is activated in Balb-neuT breast tumors in comparison to normal murine breast tissue. Knock-down of AKT3, but not of AKT1 or AKT2, led to reduced expression and tyrosine-phosphorylation of ErbB2 and ErbB3 in Balb-neuT-derived mammary tumor cells. In contrast, expression of ERα was strongly up-regulated and phosphorylation of the AKT substrate Foxo3a which regulates ERα transcription was decreased in AKT3 knockdown cells. These data suggest that ERα expression is down regulated via AKT3/Foxo3a signaling in ErbB2(+) breast cancer cells. Furthermore, up-regulation of ERα after depletion of AKT3 resulted in a significant increase in Tamoxifen responsiveness of Balb-neuT-derived mammary tumor cells. In addition, Tamoxifen resistant human breast cancer cell lines showed increased AKT3 expression and activity in comparison to Tamoxifen responsive MCF-7 cells. Finally, by AKT isoform specific in vitro kinase assays of human breast cancer samples, AKT3 activity was detected in ErbB2(+) and triple negative tumors but not in ERα(+) breast cancer. Our data indicate that AKT3 regulates the expression of ErbB2, ErbB3 and ERα and demonstrate that down-regulation of activated AKT3 can sensitize ErbB2(+) breast cancer cells for treatment with Tamoxifen. Therefore, AKT3 targeting might be a new promising strategy for therapy of ErbB2(+)/ERα(-) breast cancer and might further increase the responsiveness to an endocrine therapy approach.

Richard A Roth - One of the best experts on this subject based on the ideXlab platform.

  • up regulation of akt3 in estrogen receptor deficient breast cancers and androgen independent prostate cancer lines
    Journal of Biological Chemistry, 1999
    Co-Authors: Kaname Nakatani, Hiroshi Sakaue, Devon A Thompson, Ronald J Weigel, Andreas Barthel, Richard A Roth
    Abstract:

    Abstract We measured the insulin-stimulated amount of AKT1, Akt2, and Akt3 enzymatic activities in four breast cancer cell lines and three prostate cancer cell lines. In the estrogen receptor-deficient breast cancer cells and the androgen-insensitive prostate cells, the amount of Akt3 enzymatic activity was approximately 20–60-fold higher than in the cells that were estrogen- or androgen-responsive. In contrast, the levels of AKT1 and -2 were not increased in these cells. The increase in Akt3 enzyme activity correlated with an increase in both Akt3 mRNA and protein. In a prostate cancer cell line lacking the tumor suppressor PTEN (a lipid and protein phosphatase), the basal enzymatic activity of Akt3 was constitutively elevated and represented the major active Akt in these cells. Finally, reverse transcription-PCR was used to examine the Akt3 expression in 27 primary breast carcinomas. The expression levels of Akt3 were significantly higher in the estrogen receptor-negative tumors in comparison to the estrogen receptor-positive tumors. To see if the increase in Akt3 could be due to chromosomal abnormalities, the Akt3 gene was assigned to human chromosome 1q44 by fluorescence in situ hybridization and radiation hybrid cell panel analyses. These results indicate that Akt3 may contribute to the more aggressive clinical phenotype of the estrogen receptor-negative breast cancers and androgen-insensitive prostate carcinomas.

  • identification of a human akt3 protein kinase b γ which contains the regulatory serine phosphorylation site
    Biochemical and Biophysical Research Communications, 1999
    Co-Authors: Kaname Nakatani, Hiroshi Sakaue, Devon A Thompson, Ronald J Weigel, Richard A Roth
    Abstract:

    Abstract The family of protein kinases called Akt, protein kinase B (PKB), or related to A and C kinase (RAC) have been implicated in numerous biological processes including adipocyte and muscle differentiation, glycogen synthesis, glucose uptake, apoptosis and cellular proliferation. There are 3 known isoforms of this enzyme in mammalian cells (1/α, 2/β and 3/γ). AKT1 and 2 contain a key regulatory serine phosphorylation site in the carboxy-terminal region of the protein. However, the reported sequence of the rat Akt3 protein differed significantly from this in that it lacked 25 amino acids in the C-terminal region, including this key regulatory serine phosphorylation site ( Biochem. Biophys. Res. Commun. 216, 526–534). In the present studies we show that the deduced sequence of human Akt3 contains this serine and that it is phosphorylated in response to insulin. These results indicate that human Akt3 is regulated similarly to AKT1 and Akt2.

  • protein kinase c modulates the insulin stimulated increase in AKT1 and akt3 activity in 3t3 l1 adipocytes
    Biochemical and Biophysical Research Communications, 1998
    Co-Authors: Andreas Barthel, Kaname Nakatani, Ajai A Dandekar, Richard A Roth
    Abstract:

    In the present studies, we have compared the properties of two members of the Akt family of ser/thr kinases, AKT1 and Akt3. First, we demonstrate that both 3T3-L1 fibroblasts and adipocytes express Akt3 mRNA by RT-PCR and sequencing of the resultant PCR product. Second, we show that insulin stimulates the enzymatic activity of AKT1 and Akt3 15- and 7-fold, respectively. We then investigated the ability of protein kinase C to regulate AKT1 and 3. Neither enzyme was activated by stimulation of protein kinase C, however, the insulin-stimulated increases in activity of both isozymes were found to be comparably inhibited by prior protein kinase C activation. Since this inhibition could have resulted from an interaction of the pleckstrin homology domain of the Akt with protein kinase C, we also examined the ability of a mutant AKT1 lacking this domain to be regulated by this enzyme. The insulin-stimulated increase in enzymatic activity of this mutant Akt was regulated by PKC activation like the wild type enzyme. These results indicate that AKT1 and 3 are similarly stimulated by insulin and this stimulation is inhibited by prior activation of protein kinase C through a mechanism that is independent of the presence of the pleckstrin homology domain.

Philip N Tsichlis - One of the best experts on this subject based on the ideXlab platform.

  • abstract 4777 a phosphoproteomics analysis reveals akt isoform specific signals that link rna splicing to non small cell lung cancer
    Cancer Research, 2014
    Co-Authors: Ioannis Sanidas, Christos Polytarchou, Maria Hatziapostolou, Scott A Ezell, Michael J Comb, Dimitrios Iliopoulos, Filippos Kottakis, Ailan Guo, Jianxin Xie, Philip N Tsichlis
    Abstract:

    Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Akt isoforms exhibit different functional properties. To address the signaling differences between AKT1, Akt2 and Akt3 we examined the phosphoproteomes of a set of isogenic mouse cell lines that express different Akt isoforms. Based on this screen, we identified a total of 606 Akt phosphorylation targets, of which many are phosphorylated in an isoform specific manner. Bioinformatics analyses of these data revealed that Akt isoforms regulate differentially multiple cellular functions. One of these functions was RNA metabolism which was represented by 25 proteins phosphorylated by at least one of the Akt isoforms. One of these proteins was IWS1, which is involved in the assembly of RNA Pol II transcriptional elongation complex, and which was found to be phosphorylated at the conserved site Ser720/Thr721 by Akt3 and AKT1. Here we show that this phosphorylation event is required for the recruitment of the histone methyltransferase SETD2 to the complex and the trimethylation of histone H3 at K36 in the body of the transcribed genes. H3K36me3 provides a docking site for MRG15 and its binding partner, the splicing suppressor PTB, and regulates PTB-dependent alternative splicing. One of the targets is FGFR-2 whose alternative splicing gives rise to two isoforms, IIIb, which is expressed in epithelial cells and IIIc, which is expressed in mesenchymal cells, promotes EMT and is associated with more aggressive tumors. IWS1 phosphorylation by Akt3/AKT1 shifts splicing toward the IIIc isoform and promotes tumor growth and invasiveness both in culture and in animals. Addressing the expression of FGFR-2 in a set of lung-derived normal and tumor samples revealed that whereas the overall expression was similar in both, there was a shift toward the IIIc isoform in the tumor samples. More important, the relative expression of the IIIc and IIIb isoforms in non-small-cell-lung-carcinomas (NSCLCs) correlated with the stoichiometry of IWS1 phosphorylation and the latter correlated with Akt phosphorylation and Akt3 expression. These findings combined, underpin the importance of this pathway in the pathogenesis of lung cancer. Overall, our data suggest that Akt isoform-dependent phosphorylation events are essential for RNA processing and provide novel insights into the role of Akt in carcinogenesis. Citation Format: Ioannis Sanidas, Christos Polytarchou, Maria Hatziapostolou, Scott A. Ezell, Filippos Kottakis, Lan Hu, Ailan Guo, Jianxin Xie, Michael J. Comb, Dimitrios Iliopoulos, Philip N. Tsichlis. A phosphoproteomics analysis reveals Akt isoform-specific signals that link RNA splicing to non-small cell lung cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4777. doi:10.1158/1538-7445.AM2014-4777

  • The protein kinase AKT1 regulates the interferon response through phosphorylation of the transcriptional repressor EMSY.
    Proceedings of the National Academy of Sciences of the United States of America, 2012
    Co-Authors: Scott A Ezell, Teeru Bihani, George Sourvinos, Ioannis Sanidas, Christos Polytarchou, Maria Hatziapostolou, Michael J Comb, Philip N Tsichlis
    Abstract:

    The protein kinases AKT1, Akt2, and Akt3 possess nonredundant signaling properties, few of which have been investigated. Here, we present evidence for an AKT1-dependent pathway that controls interferon (IFN)-regulated gene expression and antiviral immunity. The target of this pathway is EMSY, an oncogenic interacting partner of BRCA2 that functions as a transcriptional repressor. Overexpression of EMSY in hTERT-immortalized mammary epithelial cells, and in breast and ovarian carcinoma cell lines, represses IFN-stimulated genes (ISGs) in a BRCA2-dependent manner, whereas its knockdown has the opposite effect. EMSY binds to the promoters of ISGs, suggesting that EMSY functions as a direct transcriptional repressor. AKT1, but not Akt2, phosphorylates EMSY at Ser209, relieving EMSY-mediated ISG repression. The AKT1/EMSY/ISG pathway is activated by both viral infection and IFN, and it inhibits the replication of HSV-1 and vesicular stomatitis virus (VSV). Collectively, these data define an AKT1-dependent pathway that contributes to the full activation of ISGs by relieving their repression by EMSY and BRCA2.

  • akt2 regulates all akt isoforms and promotes resistance to hypoxia through induction of mir 21 upon oxygen deprivation
    Cancer Research, 2011
    Co-Authors: Christos Polytarchou, Maria Hatziapostolou, Ioanna G Maroulakou, Dimitrios Iliopoulos, Filippos Kottakis, Kevin Struhl, Philip N Tsichlis
    Abstract:

    The growth and survival of tumor cells in an unfavorable hypoxic environment depend upon their adaptibility. Here we show that both normal and tumor cells expressing the protein kinase Akt2 are more resistant to hypoxia than cells expressing AKT1 or Akt3. This is due to the differential regulation of miR-21, which is upregulated by hypoxia only in Akt2-expressing cells. By upregulating miR-21 upon oxygen deprivation, Akt2 downregulates PTEN and activates all three Akt isoforms. MiR-21 also targets PDCD4 and Spry1, and the combined downregulation of these proteins with PTEN is sufficient to confer resistance to hypoxia. Furthermore, the miR-21 induction by Akt2 during hypoxia depends upon the binding of NF-κB, CREB and CBP/p300 to the miR-21 promoter, in addition to the regional acetylation of histone H3K9, all of which are under the control of Akt2. Analysis of the Akt2-miR-21 pathway in hypoxic MMTV-PyMT-induced mouse mammary adenocarcinomas and human ovarian carcinomas confirmed the activity of the pathway in vivo. Taken together, this study identifies a novel Akt2-dependent pathway that is activated by hypoxia and promotes tumor resistance via induction of miR-21.

  • micrornas differentially regulated by akt isoforms control emt and stem cell renewal in cancer cells
    Science Signaling, 2009
    Co-Authors: Dimitrios Iliopoulos, Christos Polytarchou, Maria Hatziapostolou, Ioanna G Maroulakou, Filippos Kottakis, Kevin Struhl, Philip N Tsichlis
    Abstract:

    Although Akt is known to play a role in human cancer, the relative contribution of its three isoforms to oncogenesis remains to be determined. We expressed each isoform individually in an AKT1 −/− / Akt2 −/− / Akt3 −/− cell line. MicroRNA profiling of growth factor–stimulated cells revealed unique microRNA signatures for cells with each isoform. Among the differentially regulated microRNAs, the abundance of the miR-200 family was decreased in cells bearing Akt2. Knockdown of AKT1 in transforming growth factor–β (TGFβ)–treated MCF10A cells also decreased the abundance of miR-200; however, knockdown of Akt2, or of both AKT1 and Akt2, did not. Furthermore, AKT1 knockdown in MCF10A cells promoted TGFβ-induced epithelial-mesenchymal transition (EMT) and a stem cell–like phenotype. Carcinomas developing in MMTV-cErbB2/ AKT1 −/− mice showed increased invasiveness because of miR-200 down-regulation. Finally, the ratio of AKT1 to Akt2 and the abundance of miR-200 and of the messenger RNA encoding E-cadherin in a set of primary and metastatic human breast cancers were consistent with the hypothesis that in many cases breast cancer metastasis may be under the control of the Akt–miR-200–E-cadherin axis. We conclude that induction of EMT is controlled by microRNAs whose abundance depends on the balance between AKT1 and Akt2 rather than on the overall activity of Akt.

  • AKT1 ablation inhibits whereas akt2 ablation accelerates the development of mammary adenocarcinomas in mouse mammary tumor virus mmtv erbb2 neu and mmtv polyoma middle t transgenic mice
    Cancer Research, 2007
    Co-Authors: Ioanna G Maroulakou, William Oemler, Stephen P Naber, Philip N Tsichlis
    Abstract:

    Ample evidence to date links the phosphatidylinositol 3-kinase–regulated protein kinase Akt with the induction and progression of human cancer, including breast cancer. However, there are three Akt isoforms with limited information about their specificity during oncogenesis. This study addresses the role of the three isoforms in polyoma middle T (PyMT) and ErbB2/Neu-driven mammary adenocarcinomas in mice. The effects of ablation of AKT1, Akt2, and Akt3 on the induction and the biology of these tumors were dramatically different, with ablation of AKT1 inhibiting, ablation of Akt2 accelerating, and ablation of Akt3 having a small, not statistically significant, inhibitory effect on tumor induction by both transgenes. Whereas PyMT-induced tumors are all invasive, AKT1 −/− Neu–induced tumors are more invasive than Akt2 −/− Neu–induced tumors. Invasiveness, however, does not always correlate with metastasis. Ablation of individual Akt isoforms does not affect the development of the mammary gland during puberty or the expression of the transgenes. Akt ablation, therefore, influences tumor induction by modulating transgene-induced oncogenic signaling. Immunostaining for Ki-67 and cyclin D1 and terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling assays on tissue sections revealed that the delay of tumor induction in AKT1 knockout mice is due to the inhibitory effects of AKT1 ablation on cell proliferation and survival. Given that these animal models exhibit significant similarities to human breast cancer, the results of the present study may have significant translational implications because they may influence how Akt inhibitors will be used in the treatment of human cancer. [Cancer Res 2007;67(1):167–77]