101
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Shinmura K, Kiyose S, Nagura K, Igarashi H, Inoue Y, Nakamura S, Maeda M, Baba M, Konno H, Sugimura H. TNK2 gene amplification is a novel predictor of a poor prognosis in patients with gastric cancer. J Surg Oncol 2013; 109:189-97. [PMID: 24178904 DOI: 10.1002/jso.23482] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 10/10/2013] [Indexed: 01/15/2023]
Abstract
BACKGROUNDS AND OBJECTIVES We previously examined the amplification status of 10 kinase genes (PIK3CA, EPHB3, TNK2, PTK7, EGFR, MET, ERBB2, HCK, SRC, and AURKA) in gastric cancer (GC). This study aimed to determine the prognostic significance of these gene amplifications in GC. METHODS A survival analysis was performed for GC patients. Since TNK2 amplification was identified as a prognostic marker in the analysis, we also examined the functional effect of TNK2 overexpression on gastric cells. RESULTS A Kaplan-Meier analysis showed that the prognosis of patients with GC exhibiting TNK2 or AURKA amplification was significantly poorer than the prognosis of patients with GC without TNK2 or AURKA amplification. A further multivariate analysis revealed that TNK2 amplification was an independent predictor of a poor survival outcome among patients with GC (hazard ratio, 3.668; 95% confidence interval, 1.513-7.968; P = 0.0056). TNK2-overexpressing GC cells showed an increase in cell migration and non-anchored cell growth. Finally, microarray and pathway analyses revealed the aberrant regulation of some cancer-related pathways in TNK2-overexpressing GC cells. CONCLUSIONS These results suggested that TNK2 amplification is an independent predictor of a poor prognosis in patients with GC and leads to an increase in the malignant potential of GC cells.
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Affiliation(s)
- Kazuya Shinmura
- Department of Tumor Pathology, Hamamatsu University School of Medicine, Hamamatsu, Japan
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102
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NSC126188 induces apoptosis of prostate cancer PC-3 cells through inhibition of Akt membrane translocation, FoxO3a activation, and RhoB transcription. Apoptosis 2013; 19:179-90. [DOI: 10.1007/s10495-013-0905-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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103
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Lopez SM, Hodgson MC, Packianathan C, Bingol-Ozakpinar O, Uras F, Rosen BP, Agoulnik IU. Determinants of the tumor suppressor INPP4B protein and lipid phosphatase activities. Biochem Biophys Res Commun 2013; 440:277-82. [PMID: 24070612 DOI: 10.1016/j.bbrc.2013.09.077] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 09/13/2013] [Indexed: 02/08/2023]
Abstract
The tumor suppressor INPP4B is an important regulator of phosphatidyl-inositol signaling in the cell. Reduced INPP4B expression is associated with poor outcomes for breast, prostate, and ovarian cancer patients. INPP4B contains a CX5R catalytic motif characteristic of dual-specificity phosphatases, such as PTEN. Lipid phosphatase activity of INPP4B has previously been described. In this report we show that INPP4B can dephosphorylate para-nitrophenyl phosphate (pNPP) and 6,8-difluoro-4-methylumbelliferyl (DiFMUP), synthetic phosphotyrosine analogs, suggesting that INPP4B has protein tyrosine phosphatase (PTP) activity. Using mutagenesis, we examined the functional role of specific amino acids within the INPP4B C842KSAKDR catalytic site. The K843M mutant displayed increased pNPP hydrolysis, the K846M mutant lost lipid phosphatase activity with no effect on PTP activity, and the D847E substitution ablated PTP activity and significantly reduced lipid phosphatase activity. Further, we show that INPP4B but not PTEN is able to reduce tyrosine phosphorylation of Akt1 and both the lipid and PTP activity of INPP4B likely contribute to the reduction of Akt1 phosphorylation. Taken together our data identified key residues in the INPP4B catalytic domain associated with lipid and protein phosphatase activities and found a robust downstream target regulated by INPP4B but not PTEN.
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Affiliation(s)
- Sandra M Lopez
- Department of Cell Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, 11200 SW 8th St. Miami, FL 33199, USA
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104
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Park CH, Choe H, Jang IY, Kwon SY, Latif M, Lee HK, Lee HJ, Yang EH, Yun JI, Chae CH, Cho SY, Choi SU, Ha JD, Jung H, Kim HR, Kim P, Lee CO, Yun CS, Lee K. Novel bis-ortho-alkoxy-para-piperazinesubstituted-2,4-dianilinopyrimidines (KRCA-0008) as potent and selective ALK inhibitors for anticancer treatment. Bioorg Med Chem Lett 2013; 23:6192-6. [PMID: 24095090 DOI: 10.1016/j.bmcl.2013.08.090] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 08/19/2013] [Accepted: 08/23/2013] [Indexed: 10/26/2022]
Abstract
The synthesis of bis-ortho-alkoxy-para-piperazinesubstituted-2,4-dianilinopyrimidines is described and their structure-activity-relationship to anaplastic lymphoma kinase (ALK) is presented. KRCA-0008 is selective and potent to ALK and Ack1, and displays drug-like properties without hERG liability. KRCA-0008 demonstrates in vivo efficacy comparable to Crizotinib in xenograft mice model.
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Affiliation(s)
- Chi Hoon Park
- Bio-Organic Science Division, Korea Research Institute of Chemical Technology, PO Box 107, Daejeon 305-600, Republic of Korea
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105
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Risso G, Pelisch F, Pozzi B, Mammi P, Blaustein M, Colman-Lerner A, Srebrow A. Modification of Akt by SUMO conjugation regulates alternative splicing and cell cycle. Cell Cycle 2013; 12:3165-74. [PMID: 24013425 DOI: 10.4161/cc.26183] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Akt/PKB is a key signaling molecule in higher eukaryotes and a crucial protein kinase in human health and disease. Phosphorylation, acetylation, and ubiquitylation have been reported as important regulatory post-translational modifications of this kinase. We describe here that Akt is modified by SUMO conjugation, and show that lysine residues 276 and 301 are the major SUMO attachment sites within this protein. We found that phosphorylation and SUMOylation of Akt appear as independent events. However, decreasing Akt SUMOylation levels severely affects the role of this kinase as a regulator of fibronectin and Bcl-x alternative splicing. Moreover, we observed that the Akt mutant (Akt E17K) found in several human tumors displays increased levels of SUMOylation and also an enhanced capacity to regulate fibronectin splicing patterns. This splicing regulatory activity is completely abolished by decreasing Akt E17K SUMO conjugation levels. Additionally, we found that SUMOylation controls Akt regulatory function at G₁/S transition during cell cycle progression. These findings reveal SUMO conjugation as a novel level of regulation for Akt activity, opening new areas of exploration related to the molecular mechanisms involved in the diverse cellular functions of this kinase.
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Affiliation(s)
- Guillermo Risso
- Instituto de Fisiología, Biología Molecular y Neurociencias-Consejo Nacional de Investigaciones Científicas y Técnicas; Departamento de Fisiología, Biología Molecular y Celular; Facultad de Ciencias Exactas y Naturales-Universidad de Buenos Aires; Buenos Aires, Argentina
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106
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Roppenser B, Kwon H, Canadien V, Xu R, Devreotes PN, Grinstein S, Brumell JH. Multiple host kinases contribute to Akt activation during Salmonella infection. PLoS One 2013; 8:e71015. [PMID: 23990921 PMCID: PMC3750030 DOI: 10.1371/journal.pone.0071015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 06/24/2013] [Indexed: 01/05/2023] Open
Abstract
SopB is a type 3 secreted effector with phosphatase activity that Salmonella employs to manipulate host cellular processes, allowing the bacteria to establish their intracellular niche. One important function of SopB is activation of the pro-survival kinase Akt/protein kinase B in the infected host cell. Here, we examine the mechanism of Akt activation by SopB during Salmonella infection. We show that SopB-mediated Akt activation is only partially sensitive to PI3-kinase inhibitors LY294002 and wortmannin in HeLa cells, suggesting that Class I PI3-kinases play only a minor role in this process. However, depletion of PI(3,4) P2/PI(3-5) P3 by expression of the phosphoinositide 3-phosphatase PTEN inhibits Akt activation during Salmonella invasion. Therefore, production of PI(3,4) P2/PI(3-5) P3 appears to be a necessary event for Akt activation by SopB and suggests that non-canonical kinases mediate production of these phosphoinositides during Salmonella infection. We report that Class II PI3-kinase beta isoform, IPMK and other kinases identified from a kinase screen all contribute to Akt activation during Salmonella infection. In addition, the kinases required for SopB-mediated activation of Akt vary depending on the type of infected host cell. Together, our data suggest that Salmonella has evolved to use a single effector, SopB, to manipulate a remarkably large repertoire of host kinases to activate Akt for the purpose of optimizing bacterial replication in its host.
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Affiliation(s)
- Bernhard Roppenser
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Hyunwoo Kwon
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Veronica Canadien
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Risheng Xu
- Department of Neuroscience, Johns Hopkins Medical School, Baltimore, Maryland, United States of America
| | - Peter N. Devreotes
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Sergio Grinstein
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - John H. Brumell
- Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
- Sickkids IBD Centre, Hospital for Sick Children, Toronto, Ontario, Canada
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107
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Guo H, Gao M, Lu Y, Liang J, Lorenzi PL, Bai S, Hawke DH, Li J, Dogruluk T, Scott KL, Jonasch E, Mills GB, Ding Z. Coordinate phosphorylation of multiple residues on single AKT1 and AKT2 molecules. Oncogene 2013; 33:3463-72. [PMID: 23912456 DOI: 10.1038/onc.2013.301] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 06/04/2013] [Accepted: 06/11/2013] [Indexed: 12/14/2022]
Abstract
Aberrant AKT activation is prevalent across multiple human cancer lineages providing an important new target for therapy. Twenty-two independent phosphorylation sites have been identified on specific AKT isoforms likely contributing to differential isoform regulation. However, the mechanisms regulating phosphorylation of individual AKT isoform molecules have not been elucidated because of the lack of robust approaches able to assess phosphorylation of multiple sites on a single AKT molecule. Using a nanofluidic proteomic immunoassay (NIA), consisting of isoelectric focusing followed by sensitive chemiluminescence detection, we demonstrate that under basal and ligand-induced conditions that the pattern of phosphorylation events is markedly different between AKT1 and AKT2. Indeed, there are at least 12 AKT1 peaks and at least 5 AKT2 peaks consistent with complex combinations of phosphorylation of different sites on individual AKT molecules. Following insulin stimulation, AKT1 was phosphorylated at Thr308 in the T-loop and Ser473 in the hydrophobic domain. In contrast, AKT2 was only phosphorylated at the equivalent sites (Thr309 and Ser474) at low levels. Further, Thr308 and Ser473 phosphorylation occurred predominantly on the same AKT1 molecules, whereas Thr309 and Ser474 were phosphorylated primarily on different AKT2 molecules. Although basal AKT2 phosphorylation was sensitive to inhibition of phosphatidylinositol 3-kinase (PI3K), basal AKT1 phosphorylation was essentially resistant. PI3K inhibition decreased pThr451 on AKT2 but not pThr450 on AKT1. Thus, NIA technology provides an ability to characterize coordinate phosphorylation of individual AKT molecules providing important information about AKT isoform-specific phosphorylation, which is required for optimal development and implementation of drugs targeting aberrant AKT activation.
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Affiliation(s)
- H Guo
- Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - M Gao
- Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Y Lu
- Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - J Liang
- Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - P L Lorenzi
- Department of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - S Bai
- Department of Genitourinary Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - D H Hawke
- Department of Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - J Li
- Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - T Dogruluk
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - K L Scott
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - E Jonasch
- Department of Genitourinary Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - G B Mills
- Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Z Ding
- Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
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108
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Blaustein M, Pérez-Munizaga D, Sánchez MA, Urrutia C, Grande A, Risso G, Srebrow A, Alfaro J, Colman-Lerner A. Modulation of the Akt pathway reveals a novel link with PERK/eIF2α, which is relevant during hypoxia. PLoS One 2013; 8:e69668. [PMID: 23922774 PMCID: PMC3726764 DOI: 10.1371/journal.pone.0069668] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 06/11/2013] [Indexed: 12/31/2022] Open
Abstract
The unfolded protein response (UPR) and the Akt signaling pathway share several regulatory functions and have the capacity to determine cell outcome under specific conditions. However, both pathways have largely been studied independently. Here, we asked whether the Akt pathway regulates the UPR. To this end, we used a series of chemical compounds that modulate PI3K/Akt pathway and monitored the activity of the three UPR branches: PERK, IRE1 and ATF6. The antiproliferative and antiviral drug Akt-IV strongly and persistently activated all three branches of the UPR. We present evidence that activation of PERK/eIF2α requires Akt and that PERK is a direct Akt target. Chemical activation of this novel Akt/PERK pathway by Akt-IV leads to cell death, which was largely dependent on the presence of PERK and IRE1. Finally, we show that hypoxia-induced activation of eIF2α requires Akt, providing a physiologically relevant condition for the interaction between Akt and the PERK branch of the UPR. These data suggest the UPR and the Akt pathway signal to one another as a means of controlling cell fate.
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Affiliation(s)
- Matías Blaustein
- Instituto de Fisiología, Biología Molecular y Neurociencias, Consejo Nacional de Investigaciones Científicas y Técnicas y Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Daniela Pérez-Munizaga
- Fundación Ciencia y Vida, Santiago de Chile, Chile
- Facultad de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile
| | - Manuel Alejandro Sánchez
- Instituto de Fisiología, Biología Molecular y Neurociencias, Consejo Nacional de Investigaciones Científicas y Técnicas y Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | | | - Alicia Grande
- Instituto de Fisiología, Biología Molecular y Neurociencias, Consejo Nacional de Investigaciones Científicas y Técnicas y Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Guillermo Risso
- Instituto de Fisiología, Biología Molecular y Neurociencias, Consejo Nacional de Investigaciones Científicas y Técnicas y Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Anabella Srebrow
- Instituto de Fisiología, Biología Molecular y Neurociencias, Consejo Nacional de Investigaciones Científicas y Técnicas y Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | | | - Alejandro Colman-Lerner
- Instituto de Fisiología, Biología Molecular y Neurociencias, Consejo Nacional de Investigaciones Científicas y Técnicas y Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
- * E-mail:
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109
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Dufour M, Dormond-Meuwly A, Pythoud C, Demartines N, Dormond O. Reactivation of AKT signaling following treatment of cancer cells with PI3K inhibitors attenuates their antitumor effects. Biochem Biophys Res Commun 2013; 438:32-7. [PMID: 23867821 DOI: 10.1016/j.bbrc.2013.07.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 07/03/2013] [Indexed: 01/22/2023]
Abstract
Targeting the phosphatidylinositol-3-kinase (PI3K) is a promising approach in cancer therapy. In particular, PI3K blockade leads to the inhibition of AKT, a major downstream effector responsible for the oncogenic activity of PI3K. However, we report here that small molecule inhibitors of PI3K only transiently block AKT signaling. Indeed, treatment of cancer cells with PI3K inhibitors results in a rapid inhibition of AKT phosphorylation and signaling which is followed by the reactivation of AKT signaling after 48 h as observed by Western blot. Reactivation of AKT signaling occurs despite effective inhibition of PI3K activity by PI3K inhibitors. In addition, wortmannin, a broad range PI3K inhibitor, did not block AKT reactivation suggesting that AKT signals independently of PI3K. In a therapeutical perspective, combining AKT and PI3K inhibitors exhibit stronger anti-proliferative and pro-apoptotic effects compared to AKT or PI3K inhibitors alone. Similarly, in a tumor xenograft mouse model, concomitant PI3K and AKT blockade results in stronger anti-cancer activity compared with either blockade alone. This study shows that PI3K inhibitors only transiently inhibit AKT which limits their antitumor activities. It also provides the proof of concept to combine PI3K inhibitors with AKT inhibitors in cancer therapy.
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Affiliation(s)
- Marc Dufour
- Department of Visceral Surgery, Lausanne University Hospital, Pavillon 4, Av. de Beaumont, 1011, Lausanne, Switzerland
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110
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Dissecting Major Signaling Pathways throughout the Development of Prostate Cancer. Prostate Cancer 2013; 2013:920612. [PMID: 23738079 PMCID: PMC3657461 DOI: 10.1155/2013/920612] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 03/25/2013] [Accepted: 03/28/2013] [Indexed: 01/28/2023] Open
Abstract
Prostate cancer (PCa) is one of the most common malignancies found in males. The development of PCa involves several mutations in prostate epithelial cells, usually linked to developmental changes, such as enhanced resistance to apoptotic death, constitutive proliferation, and, in some cases, to differentiation into an androgen deprivation-resistant phenotype, leading to the appearance of castration-resistant PCa (CRPCa), which leads to a poor prognosis in patients. In this review, we summarize recent findings concerning the main deregulations into signaling pathways that will lead to the development of PCa and/or CRPCa. Key mutations in some pathway molecules are often linked to a higher prevalence of PCa, by directly affecting the respective cascade and, in some cases, by deregulating a cross-talk node or junction along the pathways. We also discuss the possible environmental and nonenvironmental inducers for these mutations, as well as the potential therapeutic strategies targeting these signaling pathways. A better understanding of how some risk factors induce deregulation of these signaling pathways, as well as how these deregulated pathways affect the development of PCa and CRPCa, will further help in the development of new treatments and prevention strategies for this disease.
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111
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Mahajan K, Mahajan NP. ACK1 tyrosine kinase: targeted inhibition to block cancer cell proliferation. Cancer Lett 2013; 338:185-92. [PMID: 23597703 DOI: 10.1016/j.canlet.2013.04.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Revised: 04/03/2013] [Accepted: 04/08/2013] [Indexed: 01/05/2023]
Abstract
ACK1 tyrosine kinase, located on chromosome 3q29, is aberrantly activated, amplified or mutated in a wide variety of human cancers. While the deregulated kinase is oncogenic and its activation correlates with progression to metastatic stage, its inhibition causes cell cycle arrest, sensitizes cells to ionizing radiation and induces apoptosis. Oncogenicity of ACK1 is not only due to its ability to promote activation of critical pro-survival kinases and harmone receptors by phosphorylating at distinct tyrosine residues, but also by employing a similar mechanism to eliminate a tumor suppressor from cancer cells. Despite the substantial data supporting the oncogenic role of ACK1, and the potential clinical benefit of blocking ACK1 in metastatic disease, to date ACK1-specific small molecule inhibitors have not been exploited for cancer therapy. This review highlights recent advances that elucidate how cancer cells employ ACK1 kinase to their advantage and discusses some of the novel ACK1 inhibitors that have shown promise in pre-clinical studies.
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Affiliation(s)
- Kiran Mahajan
- Drug Discovery Department, Moffitt Cancer Center, 12902 Magnolia Drive, Tampa, FL 33612, USA.
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112
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Abdallah AM, Zhou X, Kim C, Shah KK, Hogden C, Schoenherr JA, Clemens JC, Chang HC. Activated Cdc42 kinase regulates Dock localization in male germ cells during Drosophila spermatogenesis. Dev Biol 2013; 378:141-53. [PMID: 23562806 DOI: 10.1016/j.ydbio.2013.02.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2012] [Revised: 02/15/2013] [Accepted: 02/16/2013] [Indexed: 11/25/2022]
Abstract
Deregulation of the non-receptor tyrosine kinase ACK1 (Activated Cdc42-associated kinase) correlates with poor prognosis in cancers and has been implicated in promoting metastasis. To further understand its in vivo function, we have characterized the developmental defects of a null mutation in Drosophila Ack, which bears a high degree of sequence similarity to mammalian ACK1 but lacks a CRIB domain. We show that Ack, while not essential for viability, is critical for sperm formation. This function depends on Ack tyrosine kinase activity and is required cell autonomously in differentiating male germ cells at or after the spermatocyte stage. Ack associates predominantly with endocytic clathrin sites in spermatocytes, but disruption of Ack function has no apparent effect on clathrin localization and receptor-mediated internalization of Boss (Bride of sevenless) protein in eye discs. Instead, Ack is required for the subcellular distribution of Dock (dreadlocks), the Drosophila homolog of the SH2- and SH3-containing adaptor protein Nck. Moreover, Dock forms a complex with Ack, and the localization of Dock in male germ cells depends on its SH2 domain. Together, our results suggest that Ack-dependent tyrosine phosphorylation recruits Dock to promote sperm differentiation.
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Affiliation(s)
- Abbas M Abdallah
- Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054, USA
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113
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Jin M, Wang J, Kleinberg A, Kadalbajoo M, Siu KW, Cooke A, Bittner MA, Yao Y, Thelemann A, Ji Q, Bhagwat S, Mulvihill KM, Rechka JA, Pachter JA, Crew AP, Epstein D, Mulvihill MJ. Discovery of potent, selective and orally bioavailable imidazo[1,5-a]pyrazine derived ACK1 inhibitors. Bioorg Med Chem Lett 2012; 23:979-84. [PMID: 23317569 DOI: 10.1016/j.bmcl.2012.12.042] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2012] [Revised: 12/12/2012] [Accepted: 12/13/2012] [Indexed: 12/25/2022]
Abstract
This Letter describes the medicinal chemistry effort towards a series of novel imidazo[1,5-a]pyrazine derived inhibitors of ACK1. Virtual screening led to the discovery of the initial hit, and subsequent exploration of structure-activity relationships and optimization of drug metabolism and pharmacokinetic properties led to the identification of potent, selective and orally bioavailable ACK1 inhibitors.
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Affiliation(s)
- Meizhong Jin
- OSI Pharmaceuticals, LLC, A Wholly-Owned Subsidiary of Astellas US LLC, 1 Bioscience Park Drive, Farmingdale, NY 11735, USA.
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114
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Buchwald M, Pietschmann K, Brand P, Günther A, Mahajan NP, Heinzel T, Krämer OH. SIAH ubiquitin ligases target the nonreceptor tyrosine kinase ACK1 for ubiquitinylation and proteasomal degradation. Oncogene 2012. [PMID: 23208506 DOI: 10.1038/onc.2012.515] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Activated Cdc42-associated kinase 1 (ACK1) is a nonreceptor tyrosine kinase linked to cellular transformation. The aberrant regulation of ACK1 promotes tumor progression and metastasis. Therefore, ACK1 is regarded as a valid target in cancer therapy. Seven in absentia homolog (SIAH) ubiquitin ligases facilitate substrate ubiquitinylation that targets proteins to the proteasomal degradation pathway. Here we report that ACK1 and SIAH1 from Homo sapiens interact in a yeast two-hybrid screen. Protein-protein interaction studies and protein degradation analyses using deletion and point mutants of ACK1 verify that SIAH1 and the related SIAH2 interact with ACK1. The association between SIAHs and ACK1 depends on the integrity of a highly conserved SIAH-binding motif located in the far C-terminus of ACK1. Furthermore, we demonstrate that the interaction of ACK1 with SIAH1 and the induction of proteasomal degradation of ACK1 by SIAH1 are independent of ACK1's kinase activity. Chemical inhibitors blocking proteasomal activity corroborate that SIAH1 and SIAH2 destabilize the ACK1 protein by inducing its proteasomal turnover. This mechanism apparently differs from the lysosomal pathway targeting ACK1 after stimulation with the epidermal growth factor. Our data also show that ACK1, but not ACK1 mutants lacking the SIAH binding motif, has a discernable negative effect on SIAH levels. Additionally, knockdown approaches targeting the SIAH2 mRNA uncover specifically that the induction of SIAH2 expression, by hormonally-induced estrogen receptor (ER) activation, decreases the levels of ACK1 in luminal human breast cancer cells. Collectively, our data provide novel insights into the molecular mechanisms modulating ACK1 and they position SIAH ubiquitin ligases as negative regulators of ACK1 in transformed cells.
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Affiliation(s)
- M Buchwald
- Institute of Biochemistry and Biophysics, Center for Molecular Biomedicine, Friedrich-Schiller University, Jena, Germany
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115
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H2B Tyr37 phosphorylation suppresses expression of replication-dependent core histone genes. Nat Struct Mol Biol 2012; 19:930-7. [PMID: 22885324 DOI: 10.1038/nsmb.2356] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 07/09/2012] [Indexed: 01/12/2023]
Abstract
Histone gene transcription is actively downregulated after completion of DNA synthesis to avoid overproduction. However, the precise mechanistic details of the cessation of histone mRNA synthesis are not clear. We found that histone H2B phosphorylation at Tyr37 occurs upstream of histone cluster 1, Hist1, during the late S phase. We identified WEE1 as the kinase that phosphorylates H2B at Tyr37. Loss of expression or inhibition of WEE1 kinase abrogated H2B Tyr37 phosphorylation with a concomitant increase in histone transcription in yeast and mammalian cells. H2B Tyr37 phosphorylation excluded binding of the transcriptional coactivator NPAT and RNA polymerase II and recruited the histone chaperone HIRA upstream of the Hist1 cluster. Taken together, our data show a previously unknown and evolutionarily conserved function for WEE1 kinase as an epigenetic modulator that marks chromatin with H2B Tyr37 phosphorylation, thereby inhibiting the transcription of multiple histone genes to lower the burden on the histone mRNA turnover machinery.
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Mahajan K, Mahajan NP. PI3K-independent AKT activation in cancers: a treasure trove for novel therapeutics. J Cell Physiol 2012; 227:3178-84. [PMID: 22307544 DOI: 10.1002/jcp.24065] [Citation(s) in RCA: 168] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
AKT/PKB serine threonine kinase, a critical signaling molecule promoting cell growth and survival pathways, is frequently dysregulated in many cancers. Although phosphatidylinositol-3-OH kinase (PI3K), a lipid kinase, is well characterized as a major regulator of AKT activation in response to a variety of ligands, recent studies highlight a diverse group of tyrosine (Ack1/TNK2, Src, PTK6) and serine/threonine (TBK1, IKBKE, DNAPKcs) kinases that activate AKT directly to promote its pro-proliferative signaling functions. While some of these alternate AKT activating kinases respond to growth factors, others respond to inflammatory and genotoxic stimuli. A common theme emerging from these studies is that aberrant or hyperactivation of these alternate kinases is often associated with malignancy. Consequently, evaluating the use of small molecular inhibitors against these alternate AKT activating kinases at earlier stages of cancer therapy may overcome the pressing problem of drug resistance surfacing especially in patients treated with PI3K inhibitors.
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Affiliation(s)
- Kiran Mahajan
- Drug Discovery Department, Moffitt Cancer Center, Tampa, Florida 33612, USA.
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Schoenherr JA, Drennan JM, Martinez JS, Chikka MR, Hall MC, Chang HC, Clemens JC. Drosophila activated Cdc42 kinase has an anti-apoptotic function. PLoS Genet 2012; 8:e1002725. [PMID: 22615583 PMCID: PMC3355085 DOI: 10.1371/journal.pgen.1002725] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Accepted: 04/05/2012] [Indexed: 01/20/2023] Open
Abstract
Activated Cdc42 kinases (Acks) are evolutionarily conserved non-receptor tyrosine kinases. Activating somatic mutations and increased ACK1 protein levels have been found in many types of human cancers and correlate with a poor prognosis. ACK1 is activated by epidermal growth factor (EGF) receptor signaling and functions to regulate EGF receptor turnover. ACK1 has additionally been found to propagate downstream signals through the phosphorylation of cancer relevant substrates. Using Drosophila as a model organism, we have determined that Drosophila Ack possesses potent anti-apoptotic activity that is dependent on Ack kinase activity and is further activated by EGF receptor/Ras signaling. Ack anti-apoptotic signaling does not function through enhancement of EGF stimulated MAP kinase signaling, suggesting that it must function through phosphorylation of some unknown effector. We isolated several putative Drosophila Ack interacting proteins, many being orthologs of previously identified human ACK1 interacting proteins. Two of these interacting proteins, Drk and yorkie, were found to influence Ack signaling. Drk is the Drosophila homolog of GRB2, which is required to couple ACK1 binding to receptor tyrosine kinases. Drk knockdown blocks Ack survival activity, suggesting that Ack localization is important for its pro-survival activity. Yorkie is a transcriptional co-activator that is downstream of the Salvador-Hippo-Warts pathway and promotes transcription of proliferative and anti-apoptotic genes. We find that yorkie and Ack synergistically interact to produce tissue overgrowth and that yorkie loss of function interferes with Ack anti-apoptotic signaling. Our results demonstrate how increased Ack signaling could contribute to cancer when coupled to proliferative signals. A number of recent studies have uncovered an involvement of Ack family members in human cancer. The majority of these studies focus on human ACK1 and suggest that ACK1 regulates diverse cancer-relevant biological functions, including stimulation of proliferation, blocking programmed cell death, and enhancing metastasis. It is unclear from these studies whether these biological outcomes are directly controlled by ACK1 activity or if they are indirect consequences of ACK1 signaling. Using Drosophila as a model organism, our study demonstrates that Ack serves to promote cell survival by blocking programmed cell death: a mechanism of eliminating excess, damaged, or cancerous cells. We further find that Ack activity functions synergistically with cell growth signals to produce massive cellular overgrowth. Our findings define the physiological role of Ack proteins and add further support to the value of Ack family members as therapeutic drug targets for the treatment of cancer.
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Affiliation(s)
- Jessica A. Schoenherr
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - J. Michelle Drennan
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - Juan S. Martinez
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - Madhusudana Rao Chikka
- Department of Biology, Purdue University, West Lafayette, Indiana, United States of America
| | - Mark C. Hall
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - Henry C. Chang
- Department of Biology, Purdue University, West Lafayette, Indiana, United States of America
| | - James C. Clemens
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
- * E-mail:
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Mahajan K, Coppola D, Rawal B, Chen YA, Lawrence HR, Engelman RW, Lawrence NJ, Mahajan NP. Ack1-mediated androgen receptor phosphorylation modulates radiation resistance in castration-resistant prostate cancer. J Biol Chem 2012; 287:22112-22. [PMID: 22566699 DOI: 10.1074/jbc.m112.357384] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Androgen deprivation therapy has been the standard of care in prostate cancer due to its effectiveness in initial stages. However, the disease recurs, and this recurrent cancer is referred to as castration-resistant prostate cancer (CRPC). Radiotherapy is the treatment of choice; however, in addition to androgen independence, CRPC is often resistant to radiotherapy, making radioresistant CRPC an incurable disease. The molecular mechanisms by which CRPC cells acquire radioresistance are unclear. Androgen receptor (AR)-tyrosine 267 phosphorylation by Ack1 tyrosine kinase (also known as TNK2) has emerged as an important mechanism of CRPC growth. Here, we demonstrate that pTyr(267)-AR is recruited to the ATM (ataxia telangiectasia mutated) enhancer in an Ack1-dependent manner to up-regulate ATM expression. Mice engineered to express activated Ack1 exhibited a significant increase in pTyr(267)-AR and ATM levels. Furthermore, primary human CRPCs with up-regulated activated Ack1 and pTyr(267)-AR also exhibited significant increase in ATM expression. The Ack1 inhibitor AIM-100 not only inhibited Ack1 activity but also was able to suppress AR Tyr(267) phosphorylation and its recruitment to the ATM enhancer. Notably, AIM-100 suppressed Ack1 mediated ATM expression and mitigated the growth of radioresistant CRPC tumors. Thus, our study uncovers a previously unknown mechanism of radioresistance in CRPC, which can be therapeutically reversed by a new synergistic approach that includes radiotherapy along with the suppression of Ack1/AR/ATM signaling by the Ack1 inhibitor, AIM-100.
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Affiliation(s)
- Kiran Mahajan
- Department of Drug Discovery, Moffitt Cancer Center, Tampa, Florida 33612, USA
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Mahajan K, Coppola D, Chen YA, Zhu W, Lawrence HR, Lawrence NJ, Mahajan NP. Ack1 tyrosine kinase activation correlates with pancreatic cancer progression. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 180:1386-93. [PMID: 22322295 DOI: 10.1016/j.ajpath.2011.12.028] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 12/09/2011] [Accepted: 12/22/2011] [Indexed: 12/31/2022]
Abstract
Pancreatic cancer is a significant cause of cancer mortality worldwide as the disease has advanced significantly in patients before symptoms are evident. The signal transduction pathways that promote this rapid progression are not well understood. Ack1 or TNK2, an ubiquitously expressed oncogenic non-receptor tyrosine kinase, integrates signals from ligand-activated receptor tyrosine kinases to modulate intracellular signaling cascades. In the present study, we investigated the Ack1 activation profile in a pancreatic cancer tumor microarray, and observed that expression levels of activated Ack1 and pTyr284-Ack1 positively correlated with the severity of disease progression and inversely correlated with the survival of patients with pancreatic cancer. To explore the mechanisms by which Ack1 promotes tumor progression, we investigated the role of AKT/PKB, an oncogene and Ack1-interacting protein. Ack1 activates AKT directly in pancreatic and other cancer cell lines by phosphorylating AKT at Tyr176 to promote cell survival. In addition, the Ack1 inhibitor AIM-100 not only inhibited Ack1 activation but also suppressed AKT tyrosine phosphorylation, leading to cell cycle arrest in the G1 phase. This effect resulted in a significant decrease in the proliferation of pancreatic cancer cells and induction of apoptosis. Collectively, our data indicate that activated Ack1 could be a prognostic marker for ascertaining early or advanced pancreatic cancer. Thus, Ack1 inhibitors hold promise for therapeutic intervention to inhibit pancreatic tumor growth.
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Affiliation(s)
- Kiran Mahajan
- Department of Drug Discovery, Moffitt Cancer Center, Tampa, Florida 33612, USA
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Qiu W, Zhang Y, Liu X, Zhou J, Li Y, Zhou Y, Shan K, Xia M, Che N, Feng X, Zhao D, Wang Y. Sublytic C5b-9 complexes induce proliferative changes of glomerular mesangial cells in rat Thy-1 nephritis through TRAF6-mediated PI3K-dependent Akt1 activation. J Pathol 2011; 226:619-32. [PMID: 21984198 DOI: 10.1002/path.3011] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 07/21/2011] [Accepted: 08/12/2011] [Indexed: 12/20/2022]
Abstract
The proliferation of glomerular mesangial cells (GMCs) and secretion of extracellular matrix (ECM) in rat Thy-1 nephritis (Thy-1N), resembling human mesangioproliferative glomerulonephritis (MsPGN), have been studied for many years, but the mechanisms, especially the role of signalling pathway activation and its regulation in GMCs triggered by sublytic C5b-9 complexes in Thy-1N rats remain largely unclear. In the study, the proliferation of GMCs and production of ECM as well as the role of PI3K/Akt and its regulation, both in GMCs induced by sublytic C5b-9 (in vitro) and in the renal tissues of rats with Thy-1N (in vivo), were determined and the results revealed that GMCs proliferation and ECM secretion, both in vitro and in vivo, were notably increased, and that PI3K/Akt1 activation and its regulation, such as TNF receptor-associated factor 6 (TRAF6)-mediated Akt1 ubiquitination and PI3K-dependent Akt1 phosphorylation, were involved in the process of Thy-1N induction. On the other hand, silence of the TRAF6, PI3K or Akt1 genes could obviously diminish the proliferative damages and urinary protein secretion of Thy-1N rats. Together, these data implicated that sublytic C5b-9 complexes in Thy-1N rats could promote GMCs proliferation and ECM production through TRAF6-mediated PI3K-dependent Akt1 activation, in which the ubiquitination and phosphorylation of the Akt1 signal molecule played an important role in the initiation and development of the proliferative changes in the rats with Thy-1N.
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Affiliation(s)
- Wen Qiu
- Department of Immunology and Lab of Immunopathology, Nanjing Medical University, People's Republic of China
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Regulation of ack-family nonreceptor tyrosine kinases. JOURNAL OF SIGNAL TRANSDUCTION 2011; 2011:742372. [PMID: 21637378 PMCID: PMC3101793 DOI: 10.1155/2011/742372] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 01/13/2011] [Indexed: 01/17/2023]
Abstract
Ack family non-receptor tyrosine kinases are unique with regard to their domain composition and regulatory properties. Human Ack1 (activated Cdc42-associated kinase) is ubiquitously expressed and is activated by signals that include growth factors and integrin-mediated cell adhesion. Stimulation leads to Ack1 autophosphorylation and to phosphorylation of additional residues in the C-terminus. The N-terminal SAM domain is required for full activation. Ack1 exerts some of its effects via protein-protein interactions that are independent of its kinase activity. In the basal state, Ack1 activity is suppressed by an intramolecular interaction between the catalytic domain and the C-terminal region. Inappropriate Ack1 activation and signaling has been implicated in the development, progression, and metastasis of several forms of cancer. Thus, there is increasing interest in Ack1 as a drug target, and studies of the regulatory properties of the enzyme may reveal features that can be exploited in inhibitor design.
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Mahajan K, Challa S, Coppola D, Lawrence H, Luo Y, Gevariya H, Zhu W, Chen YA, Lawrence NJ, Mahajan NP. Effect of Ack1 tyrosine kinase inhibitor on ligand-independent androgen receptor activity. Prostate 2010; 70:1274-85. [PMID: 20623637 PMCID: PMC3953126 DOI: 10.1002/pros.21163] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
BACKGROUND Androgen receptor (AR) plays a critical role in the progression of both androgen-dependent and androgen-independent prostate cancer (AIPC). Ligand-independent activation of AR in AIPC or castration resistant prostate cancer (CRPC) is often associated with poor prognosis. Recently, tyrosine kinase Ack1 has been shown to regulate AR activity by phosphorylating it at tyrosine 267 and this event was shown to be critical for AIPC growth. However, whether a small molecule inhibitor that can mitigate Ack1 activation is sufficient to abrogate AR activity on AR regulated promoters in androgen-depleted environment is not known. METHODS We have generated two key resources, antibodies that specifically recognize pTyr267-AR and synthesized a small molecule inhibitor of Ack1, 4-amino-5,6-biaryl-furo[2,3-d]pyrimidine (named here as AIM-100) to test whether AIM-100 modulates ligand-independent AR activity and inhibits prostate cell growth. RESULTS Prostate tissue microarray analysis indicates that Ack1 Tyr284 phosphorylation correlates positively with disease progression and negatively with the survival of prostate cancer patients. Interestingly, neither pTyr267-AR expression nor its transcriptional activation was affected by anti-androgens in activated Ack1 expressing or EGF stimulated prostate cells. However, the Ack1 inhibitor, AIM-100, not only inhibited Ack1 activation but also able to suppress pTyr267-AR phosphorylation, binding of AR to PSA, NKX3.1, and TMPRSS2 promoters, and inhibit AR transcription activity. CONCLUSION Ack1 Tyr284 phosphorylation is prognostic of progression of prostate cancer and inhibitors of Ack1 activity could be novel therapeutic agents to treat AIPC.
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Affiliation(s)
- Kiran Mahajan
- Drug Discovery Department, Moffitt Cancer Center, Tampa, Florida
| | - Sridevi Challa
- Drug Discovery Department, Moffitt Cancer Center, Tampa, Florida
| | - Domenico Coppola
- Department of Anatomic Pathology, Moffitt Cancer Center, Tampa, Florida
| | - Harshani Lawrence
- Drug Discovery Department, Moffitt Cancer Center, Tampa, Florida
- HighThroughput Screening and Chemistry Core, Moffitt Cancer Center, Tampa, Florida
| | - Yunting Luo
- HighThroughput Screening and Chemistry Core, Moffitt Cancer Center, Tampa, Florida
| | - Harsukh Gevariya
- Drug Discovery Department, Moffitt Cancer Center, Tampa, Florida
| | - Weiwei Zhu
- Department of Biostatistics, Moffitt Cancer Center, Tampa, Florida
| | - Y. Ann Chen
- Department of Biostatistics, Moffitt Cancer Center, Tampa, Florida
| | | | - Nupam P. Mahajan
- Drug Discovery Department, Moffitt Cancer Center, Tampa, Florida
- Correspondence to: Nupam P. Mahajan, Drug Discovery Department, Moffitt Cancer Center, 12902 Magnolia Drive, Tampa, Florida 33612, USA.
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Protein tyrosine kinase 6 directly phosphorylates AKT and promotes AKT activation in response to epidermal growth factor. Mol Cell Biol 2010; 30:4280-92. [PMID: 20606012 DOI: 10.1128/mcb.00024-10] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Protein tyrosine kinase 6 (PTK6) is a nonmyristoylated Src-related intracellular tyrosine kinase. Although not expressed in the normal mammary gland, PTK6 is expressed in a majority of human breast tumors examined, and it has been linked to ErbB receptor signaling and AKT activation. Here we demonstrate that AKT is a direct substrate of PTK6 and that AKT tyrosine residues 315 and 326 are phosphorylated by PTK6. Association of PTK6 with AKT occurs through the SH3 domain of PTK6 and is enhanced through SH2 domain-mediated interactions following tyrosine phosphorylation of AKT. Using Src, Yes, and Fyn null mouse embryonic fibroblasts (SYF cells), we show that PTK6 phosphorylates AKT in a Src family kinase-independent manner. Introduction of PTK6 into SYF cells sensitized these cells to physiological levels of epidermal growth factor (EGF) and increased AKT activation. Stable introduction of active PTK6 into SYF cells also resulted in increased proliferation. Knockdown of PTK6 in the BPH-1 human prostate epithelial cell line led to decreased AKT activation in response to EGF. Our data indicate that in addition to promoting growth factor receptor-mediated activation of AKT, PTK6 can directly activate AKT to promote oncogenic signaling.
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Mahajan K, Mahajan NP. Shepherding AKT and androgen receptor by Ack1 tyrosine kinase. J Cell Physiol 2010; 224:327-33. [PMID: 20432460 DOI: 10.1002/jcp.22162] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Ack1 (also known as ACK, TNK2, or activated Cdc42 kinase) is a structurally unique non-receptor tyrosine kinase that is expressed in diverse cell types. It integrates signals from plethora of ligand-activated receptor tyrosine kinases (RTKs), for example, MERTK, EGFR, HER2, PDGFR and insulin receptor to initiate intracellular signaling cascades. Ack1 transduces extracellular signals to cytosolic and nuclear effectors such as the protein kinase AKT/PKB and androgen receptor (AR), to promote cell survival and growth. While tyrosine phosphorylation of AR at Tyr267 regulates androgen-independent recruitment of AR to the androgen-responsive enhancers and transcription of AR target genes to drive prostate cancer progression, phosphorylation of an evolutionarily conserved Tyrosine 176 in the kinase domain of AKT is essential for mitotic progression and positively correlates with breast cancer progression. In contrast to AR and AKT, Ack1-mediated phosphorylation of the tumor suppressor Wwox at Tyr287 lead to rapid Wwox polyubiquitination followed by degradation. Thus, by its ability to promote tumor growth by negatively regulating tumor suppressor such as Wwox and positively regulating pro-survival factors such as AKT and AR, Ack1 is emerging as a critical player in cancer biology. In this review, we discuss recent advances in understanding the physiological functions of Ack1 signaling in normal cells and the consequences of its hyperactivation in various cancers.
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Affiliation(s)
- Kiran Mahajan
- Drug Discovery Program, Moffitt Cancer Center, Tampa, Florida 33612, USA
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