601
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Hallare AV, Ruiz PLS, Cariño JCED. Assessment of Jatropha curcas L. biodiesel seed cake toxicity using the zebrafish (Danio rerio) embryo toxicity (ZFET) test. Environ Sci Pollut Res Int 2014; 21:6044-6056. [PMID: 24464135 DOI: 10.1007/s11356-014-2539-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Accepted: 01/08/2014] [Indexed: 06/03/2023]
Abstract
Consequent to the growing demand for alternative sources of energy, the seeds from Jatropha curcas remain to be the favorite for biodiesel production. However, a significant volume of the residual organic mass (seed cake) is produced during the extraction process, which raises concerns on safe waste disposal. In the present study, we assessed the toxicity of J. curcas seed cake using the zebrafish (Danio rerio) embryotoxicity test. Within 1-h post-fertilization (hpf), the fertilized eggs were exposed to five mass concentrations of J. curcas seed cake and were followed through 24, 48, and 72 hpf. Toxicity was evaluated based on lethal endpoints induced on zebrafish embryos namely egg coagulation, non-formation of somites, and non-detachment of tail. The lowest concentration tested, 1 g/L, was not able to elicit toxicity on embryos whereas 100 % mortality (based also on lethal endpoints) was recorded at the highest concentration at 2.15 g/L. The computed LC50 for the J. curcas seed cake was 1.61 g/L. No further increase in mortality was observed in the succeeding time points (48 and 72 hpf) indicating that J. curcas seed cake exerted acute toxicity on zebrafish embryos. Sublethal endpoints (yolk sac and pericardial edema) were noted at 72 hpf in zebrafish embryos exposed to higher concentrations. The observed lethal endpoints induced on zebrafish embryos were discussed in relation to the active principles, notably, phorbol esters that have remained in the seed cake even after extraction.
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Affiliation(s)
- Arnold V Hallare
- Department of Biology, CAS, University of the Philippines, Manila, Padre Faura St., Manila, 1000, Philippines,
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602
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Abstract
Rho GTPases regulate many essential processes during development, yet the full impact of their upstream regulation through guanine nucleotide exchange factors (GEFs) is only beginning to be appreciated. In this review, Laurin and Côté focus on emerging biological functions of the mammalian Dock family of GEFs in development and disease and discuss how recent discoveries might be exploited for novel therapeutic strategies. Rho GTPases play key regulatory roles in many aspects of embryonic development, regulating processes such as differentiation, proliferation, morphogenesis, and migration. Two families of guanine nucleotide exchange factors (GEFs) found in metazoans, Dbl and Dock, are responsible for the spatiotemporal activation of Rac and Cdc42 proteins and their downstream signaling pathways. This review focuses on the emerging roles of the mammalian DOCK family in development and disease. We also discuss, when possible, how recent discoveries concerning the biological functions of these GEFs might be exploited for the development of novel therapeutic strategies.
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Affiliation(s)
- Mélanie Laurin
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, Quebec H2W 1R7, Canada
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603
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Abstract
The Dishevelled, EGL-10 and pleckstrin (DEP) domain is a globular protein domain that is present in about ten human protein families with well-defined structural features. A picture is emerging that DEP domains mainly function in the spatial and temporal control of diverse signal transduction events by recruiting proteins to the plasma membrane. DEP domains can interact with various partners at the membrane, including phospholipids and membrane receptors, and their binding is subject to regulation.
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604
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Jain K, Basu A. The Multifunctional Protein Kinase C-ε in Cancer Development and Progression. Cancers (Basel) 2014; 6:860-78. [PMID: 24727247 PMCID: PMC4074807 DOI: 10.3390/cancers6020860] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 03/27/2014] [Accepted: 04/01/2014] [Indexed: 12/31/2022] Open
Abstract
The protein kinase C (PKC) family proteins are important signal transducers and have long been the focus of cancer research. PKCɛ, a member of this family, is overexpressed in most solid tumors and plays critical roles in different processes that lead to cancer development. Studies using cell lines and animal models demonstrated the transforming potential of PKCɛ. While earlier research established the survival functions of PKCɛ, recent studies revealed its role in cell migration, invasion and cancer metastasis. PKCɛ has also been implicated in epithelial to mesenchymal transition (EMT), which may be the underlying mechanism by which it contributes to cell motility. In addition, PKCɛ affects cell-extracellular matrix (ECM) interactions by direct regulation of the cytoskeletal elements. Recent studies have also linked PKCɛ signaling to cancer stem cell functioning. This review focuses on the role of PKCɛ in different processes that lead to cancer development and progression. We also discussed current literatures on the pursuit of PKCɛ as a target for cancer therapy.
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Affiliation(s)
- Kirti Jain
- Department of Molecular and Medical Genetics, University of North Texas Health Science Center, Institute for Cancer Research, and Focused on Resources for her Health Education and Research, Fort Worth, TX 76107, USA.
| | - Alakananda Basu
- Department of Molecular and Medical Genetics, University of North Texas Health Science Center, Institute for Cancer Research, and Focused on Resources for her Health Education and Research, Fort Worth, TX 76107, USA.
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605
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Zhang Y, Gong Y, Hu D, Zhu P, Wang N, Zhang Q, Wang M, Aldeewan A, Xia H, Qu X, Ring BZ, Minato N, Su L. Nuclear SIPA1 activates integrin β1 promoter and promotes invasion of breast cancer cells. Oncogene 2015; 34:1451-62. [DOI: 10.1038/onc.2014.36] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 12/31/2013] [Accepted: 01/06/2014] [Indexed: 12/14/2022]
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606
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Damoulakis G, Gambardella L, Rossman KL, Lawson CD, Anderson KE, Fukui Y, Welch HC, Der CJ, Stephens LR, Hawkins PT. P-Rex1 directly activates RhoG to regulate GPCR-driven Rac signalling and actin polarity in neutrophils. J Cell Sci 2014; 127:2589-600. [PMID: 24659802 DOI: 10.1242/jcs.153049] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
G-protein-coupled receptors (GPCRs) regulate the organisation of the actin cytoskeleton by activating the Rac subfamily of small GTPases. The guanine-nucleotide-exchange factor (GEF) P-Rex1 is engaged downstream of GPCRs and phosphoinositide 3-kinase (PI3K) in many cell types, and promotes tumorigenic signalling and metastasis in breast cancer and melanoma, respectively. Although P-Rex1-dependent functions have been attributed to its GEF activity towards Rac1, we show that P-Rex1 also acts as a GEF for the Rac-related GTPase RhoG, both in vitro and in GPCR-stimulated primary mouse neutrophils. Furthermore, loss of either P-Rex1 or RhoG caused equivalent reductions in GPCR-driven Rac activation and Rac-dependent NADPH oxidase activity, suggesting they both function upstream of Rac in this system. Loss of RhoG also impaired GPCR-driven recruitment of the Rac GEF DOCK2, and F-actin, to the leading edge of migrating neutrophils. Taken together, our results reveal a new signalling hierarchy in which P-Rex1, acting as a GEF for RhoG, regulates Rac-dependent functions indirectly through RhoG-dependent recruitment of DOCK2. These findings thus have broad implications for our understanding of GPCR signalling to Rho GTPases and the actin cytoskeleton.
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Affiliation(s)
- George Damoulakis
- Inositide laboratory, Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, UK
| | - Laure Gambardella
- Inositide laboratory, Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, UK
| | - Kent L Rossman
- Lineberger Comprehensive Cancer Center and Department of Pharmacology, University of North Carolina at Chapel Hill, 450 West Drive, Chapel Hill, North Carolina, USA
| | - Campbell D Lawson
- Inositide laboratory, Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, UK
| | - Karen E Anderson
- Inositide laboratory, Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, UK
| | - Yoshinori Fukui
- Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
| | - Heidi C Welch
- Inositide laboratory, Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, UK
| | - Channing J Der
- Lineberger Comprehensive Cancer Center and Department of Pharmacology, University of North Carolina at Chapel Hill, 450 West Drive, Chapel Hill, North Carolina, USA
| | - Len R Stephens
- Inositide laboratory, Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, UK
| | - Phillip T Hawkins
- Inositide laboratory, Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, UK
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607
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Mlechkovich G, Peng SS, Shacham V, Martinez E, Gokhman I, Minis A, Tran TS, Yaron A. Distinct cytoplasmic domains in Plexin-A4 mediate diverse responses to semaphorin 3A in developing mammalian neurons. Sci Signal 2014; 7:ra24. [PMID: 24619647 DOI: 10.1126/scisignal.2004734] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Guidance receptor signaling is crucial for neural circuit formation and elicits diverse cellular events in specific neurons. We found that signaling from the guidance cue semaphorin 3A diverged through distinct cytoplasmic domains in its receptor Plexin-A4 to promote disparate cellular behavior in different neuronal cell types. Plexin-A4 has three main cytoplasmic domains--C1, Hinge/RBD, and C2--and interacts with family members of the Rho guanine nucleotide exchange factor FARP proteins. We show that growth cone collapse occurred in Plexin-A4-deficient dorsal root ganglion sensory neurons reconstituted with Plexin-A4 containing either the Hinge/RBD or C2 domain, whereas both of the Hinge/RBD and C1 domains were required for dendritic arborization in cortical neurons. Although knockdown studies indicated that both the collapse and arborization responses involved FARP2, mutations in the cytoplasmic region of Plexin-A4 that reduced its interaction with FARP2 strongly inhibited semaphorin 3A-induced dendritic branching but not growth cone collapse, suggesting that different degrees of interaction are required for the two responses or that developing axons have an indirect path to FARP2 activation. Thus, our study provided insights into the multifunctionality of guidance receptors, in particular showing that the semaphorin 3A signal diverges through specific functions of the modular domains of Plexin-A4.
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Affiliation(s)
- Guy Mlechkovich
- 1Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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608
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Koropouli E, Kolodkin AL. Semaphorins and the dynamic regulation of synapse assembly, refinement, and function. Curr Opin Neurobiol 2014; 27:1-7. [PMID: 24598309 DOI: 10.1016/j.conb.2014.02.005] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 01/21/2014] [Accepted: 02/06/2014] [Indexed: 01/13/2023]
Abstract
Semaphorins are phylogenetically conserved proteins expressed in most organ systems, including the nervous system. Following their description as axon guidance cues, semaphorins have been implicated in multiple aspects of nervous system development. Semaphorins are key regulators of neural circuit assembly, neuronal morphogenesis, assembly of excitatory and inhibitory synapses, and synaptic refinement. Semaphorins contribute to the balance between excitatory and inhibitory synaptic transmission, and electrical activity can modulate semaphorin signaling in neurons. This interplay between guidance cue signaling and electrical activity has the potential to sculpt the wiring of neural circuits and to modulate their function.
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609
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Wie SM, Adwan TS, DeGregori J, Anderson SM, Reyland ME. Inhibiting tyrosine phosphorylation of protein kinase Cδ (PKCδ) protects the salivary gland from radiation damage. J Biol Chem 2014; 289:10900-10908. [PMID: 24569990 DOI: 10.1074/jbc.m114.551366] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Radiation therapy for head and neck cancer can result in extensive damage to normal adjacent tissues such as the salivary gland and oral mucosa. We have shown previously that tyrosine phosphorylation at Tyr-64 and Tyr-155 activates PKCδ in response to apoptotic stimuli by facilitating its nuclear import. Here we have identified the tyrosine kinases that mediate activation of PKCδ in apoptotic cells and have explored the use of tyrosine kinase inhibitors for suppression of irradiation-induced apoptosis. We identify the damage-inducible kinase, c-Abl, as the PKCδ Tyr-155 kinase and c-Src as the Tyr-64 kinase. Depletion of c-Abl or c-Src with shRNA decreased irradiation- and etoposide-induced apoptosis, suggesting that inhibitors of these kinases may be useful therapeutically. Pretreatment with dasatinib, a broad spectrum tyrosine kinase inhibitor, blocked phosphorylation of PKCδ at both Tyr-64 and Tyr-155. Expression of "gate-keeper" mutants of c-Abl or c-Src that are active in the presence of dasatinib restored phosphorylation of PKCδ at Tyr-155 and Tyr-64, respectively. Imatinib, a c-Abl-selective inhibitor, also specifically blocked PKCδ Tyr-155 phosphorylation. Dasatinib and imatinib both blocked binding of PKCδ to importin-α and nuclear import, demonstrating that tyrosine kinase inhibitors can inhibit nuclear accumulation of PKCδ. Likewise, pretreatment with dasatinib also suppressed etoposide and radiation induced apoptosis in vitro. In vivo, pre-treatment of mice with dasatinib blocked radiation-induced apoptosis in the salivary gland by >60%. These data suggest that tyrosine kinase inhibitors may be useful prophylactically for protection of nontumor tissues in patients undergoing radiotherapy of the head and neck.
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Affiliation(s)
- Sten M Wie
- Program in Structural Biology and Biochemistry; Department of Craniofacial Biology, School of Dental Medicine, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
| | - Tariq S Adwan
- Department of Craniofacial Biology, School of Dental Medicine, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
| | - James DeGregori
- Department of Biochemistry and Molecular Genetics, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
| | - Steven M Anderson
- Department of Pathology, School of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045
| | - Mary E Reyland
- Department of Craniofacial Biology, School of Dental Medicine, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045.
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610
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Sato K, Sugiyama T, Nagase T, Kitade Y, Ueda H. Threonine 680 phosphorylation of FLJ00018/PLEKHG2, a Rho family-specific guanine nucleotide exchange factor, by epidermal growth factor receptor signaling regulates cell morphology of Neuro-2a cells. J Biol Chem 2014; 289:10045-56. [PMID: 24554703 DOI: 10.1074/jbc.m113.521880] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
FLJ00018/PLEKHG2 is a guanine nucleotide exchange factor for the small GTPases Rac and Cdc42 and has been shown to mediate the signaling pathways leading to actin cytoskeleton reorganization. The function of FLJ00018 is regulated by the interaction of heterotrimeric GTP-binding protein Gβγ subunits or cytosolic actin. However, the details underlying the molecular mechanisms of FLJ00018 activation have yet to be elucidated. In the present study we show that FLJ00018 is phosphorylated and activated by β1-adrenergic receptor stimulation-induced EGF receptor (EGFR) transactivation in addition to Gβγ signaling. FLJ00018 is also phosphorylated and activated by direct EGFR stimulation. The phosphorylation of FLJ00018 by EGFR stimulation is mediated by the Ras/mitogen-activated protein kinase (MAPK) pathway. Through deletion and site-directed mutagenesis studies, we have identified Thr-680 as the major site of phosphorylation by EGFR stimulation. FLJ00018 T680A, in which the phosphorylation site is replaced by alanine, showed a limited response of the Neuro-2a cell morphology to EGF stimulation. Our results provide evidence that stimulation of the Ras/MAPK pathway by EGFR results in FLJ00018 phosphorylation at Thr-680, which in turn controls changes in cell shape.
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Affiliation(s)
- Katsuya Sato
- From the United Graduate School of Drug Discovery and Medical Information Sciences and
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611
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Tan B, Tan J, Du H, Quan Z, Xu X, Jiang X, Luo C, Wu X. HepaCAM inhibits clear cell renal carcinoma 786-0 cell proliferation via blocking PKCε translocation from cytoplasm to plasma membrane. Mol Cell Biochem 2014; 391:95-102. [PMID: 24515280 DOI: 10.1007/s11010-014-1991-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 01/29/2014] [Indexed: 01/01/2023]
Abstract
Hepatocyte cell adhesion molecule (HepaCAM) plays a crucial role in tumor progression and has been recognized as a novel tumor suppressor gene. The high protein expression level of protein kinase Cε (PKCε) has been discovered in many tumor types. In the present study, we determined HepaCAM and PKCε protein levels in human clear cell renal cell carcinoma (ccRCC) tissues and analyzed the correlation between them. We observed an inverse relationship in the expression of HepaCAM and PKCε in ccRCC and adjacent normal tissues. In ccRCC tissue, HepaCAM expression was undetectable while PKCε expression was high; the opposite was found in the adjacent normal tissue. Western blot analysis demonstrated that PKCε cytosolic protein levels increased while plasma membrane protein levels decreased without any change in total protein following infection of the ccRCC cell line 786-0 with adenovirus-GFP-HepaCAM (Ad-GFP-HepaCAM). Moreover, the application of Ad-GFP-HepaCAM combined with a PKCε-specific translocation inhibitor (εV1-2) effectively inhibited 786-0 cell growth. Ad-mediated expression of HepaCAM in 786-0 cells reduced the levels of phosphorylated AKT and cyclin D1 and inhibited cell proliferation. In summary, our studies point to interesting connections between HepaCAM and PKCε in tissues and in vitro. HepaCAM may prevent the translocation of PKCε from cytosolic to particulate fractions, resulting in the inhibition of 786-0 cell proliferation. Therapeutic manipulation of these novel protein targets may provide new ways of treating ccRCC.
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Affiliation(s)
- Bing Tan
- Department of Urology, The First Affiliated Hospital of Chongqing Medical University, No. 1, Youyi Road, Yuanjiagang, Yuzhong District, Chongqing, 400016, People's Republic of China
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612
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Abstract
It is now well established that tumor cell invasion through tissue is strongly regulated by the microstructural and mechanical properties of the extracellular matrix (ECM). However, it remains unclear how these physical microenvironmental inputs are jointly processed with oncogenic lesions to drive invasion. In this study, we address this open question by combining a microfabricated polyacrylamide channel (μPAC) platform that enables independent control of ECM stiffness and confinement with an isogenically-matched breast tumor progression series in which the oncogenes ErbB2 and 14-3-3ζ are overexpressed independently or in tandem. We find that increasing channel confinement and overexpressing ErbB2 both promote cell migration to a similar degree when other parameters are kept constant. In contrast, 14-3-3ζ overexpression slows migration speed, and does so in a fashion that dwarfs effects of ECM confinement and stiffness. We also find that ECM stiffness dramatically enhances cell motility when combined with ErbB2 overexpression, demonstrating that biophysical cues and cell-intrinsic parameters promote cell invasion in an integrative manner. Morphometric analysis of cells inside the μPAC platform reveals that the rapid cell migration induced by narrow channels and ErbB2 overexpression are both accompanied by increased cell polarization. Disruption of this polarization occurs by pharmacological inhibition of Rac GTPase phenocopies 14-3-3ζ overexpression by reducing cell polarization and slowing migration. By systematically measuring migration speed as a function of matrix stiffness and confinement, we also quantify for the first time the sensitivity of migration speed to microchannel properties and transforming potential. These results demonstrate that oncogenic lesions and ECM biophysical properties can synergistically interact to drive invasive migration, and that both inputs may act through common molecular mechanisms to enhance migration speed.
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Affiliation(s)
- Amit Pathak
- Department of Bioengineering, University of California, Berkeley, CA 94720-1762, USA
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613
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O'Hayre M, Degese MS, Gutkind JS. Novel insights into G protein and G protein-coupled receptor signaling in cancer. Curr Opin Cell Biol 2014; 27:126-35. [PMID: 24508914 DOI: 10.1016/j.ceb.2014.01.005] [Citation(s) in RCA: 206] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Accepted: 01/13/2014] [Indexed: 12/12/2022]
Abstract
G protein-coupled receptors (GPCRs) play a central role in signal transmission, thereby controlling many facets of cellular function. Overwhelming evidence now implicates GPCRs, G proteins and their downstream signaling targets in cancer initiation and progression, where they can influence aberrant cell growth and survival, largely through activation of AKT/mTOR, MAPKs, and Hippo signaling pathways. GPCRs also play critical roles in the invasion and metastasis of cancer cells via activation of Rho GTPases and cytoskeletal changes, and angiogenesis to supply the tumor with nutrients and provide routes for metastasis. Lastly, GPCRs contribute to the establishment and maintenance of a permissive tumor microenvironment. Understanding GPCR involvement in cancer malignancy may help identify novel therapeutic opportunities for cancer prevention and treatment.
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Affiliation(s)
- Morgan O'Hayre
- Oral and Pharyngeal Cancer Branch, Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA
| | - Maria S Degese
- Oral and Pharyngeal Cancer Branch, Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA
| | - J Silvio Gutkind
- Oral and Pharyngeal Cancer Branch, Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA.
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614
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Robles-Molina E, Dionisio-Vicuña M, Guzmán-Hernández ML, Reyes-Cruz G, Vázquez-Prado J. Gβγ interacts with mTOR and promotes its activation. Biochem Biophys Res Commun 2014; 444:218-23. [PMID: 24462769 DOI: 10.1016/j.bbrc.2014.01.044] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Accepted: 01/14/2014] [Indexed: 01/09/2023]
Abstract
Diverse G protein-coupled receptors depend on Gβγ heterodimers to promote cell polarization and survival via direct activation of PI3Kγ and potentially other effectors. These events involve full activation of AKT via its phosphorylation at Ser473, suggesting that mTORC2, the kinase that phosphorylates AKT at Ser473, is activated downstream of Gβγ. Thus, we tested the hypothesis that Gβγ directly contributes to mTOR signaling. Here, we demonstrate that endogenous mTOR interacts with Gβγ. Cell stimulation with serum modulates Gβγ interaction with mTOR. The carboxyl terminal region of mTOR, expressed as a GST-fusion protein, including the serine/threonine kinase domain, binds Gβγ heterodimers containing different Gβ subunits, except Gβ4. Both, mTORC1 and mTORC2 complexes interact with Gβ₁γ₂ which promotes phosphorylation of their respective substrates, p70S6K and AKT. In addition, chronic treatment with rapamycin, a condition known to interfere with assembly of mTORC2, reduces the interaction between Gβγ and mTOR and the phosphorylation of AKT; whereas overexpression of Gαi interfered with the effect of Gβγ as promoter of p70S6K and AKT phosphorylation. Altogether, our results suggest that Gβγ positively regulates mTOR signaling via direct interactions and provide further support to emerging strategies based on the therapeutical potential of inhibiting different Gβγ signaling interfaces.
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Affiliation(s)
- Evelyn Robles-Molina
- Department of Pharmacology, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Apartado postal 14-740, México, D.F. 07360, Mexico
| | - Misael Dionisio-Vicuña
- Department of Cell Biology, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Apartado postal 14-740, México, D.F. 07360, Mexico
| | - María Luisa Guzmán-Hernández
- Department of Pharmacology, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Apartado postal 14-740, México, D.F. 07360, Mexico
| | - Guadalupe Reyes-Cruz
- Department of Cell Biology, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Apartado postal 14-740, México, D.F. 07360, Mexico
| | - José Vázquez-Prado
- Department of Pharmacology, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Apartado postal 14-740, México, D.F. 07360, Mexico.
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615
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Zubeldia-Brenner L, Gutierrez-Uzquiza A, Barrio-Real L, Wang H, Kazanietz MG, Leskow FC. β3-chimaerin, a novel member of the chimaerin Rac-GAP family. Mol Biol Rep 2014; 41:2067-76. [PMID: 24430297 DOI: 10.1007/s11033-014-3055-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 01/04/2014] [Indexed: 12/11/2022]
Abstract
Chimaerins are a family of diacylglycerol- and phorbol ester-regulated GTPase activating proteins (GAPs) for the small G-protein Rac. Extensive evidence indicates that these proteins play important roles in development, axon guidance, metabolism, cell motility, and T cell activation. Four isoforms have been reported to-date, which are products of CHN1 (α1- and α2-chimaerins) and CHN2 (β1- and β2-chimaerins) genes. Although these gene products are assumed to be generated by alternative splicing, bioinformatics analysis of the CHN2 gene revealed that β1- and β2-chimaerins are the products of alternative transcription start sites (TSSs) in different promoter regions. Furthermore, we found an additional TSS in CHN2 gene that leads to a novel product, which we named β3-chimaerin. Expression profile analysis revealed predominantly low levels for the β3-chimaerin transcript, with higher expression levels in epididymis, plasma blood leucocytes, spleen, thymus, as well as various areas of the brain. In addition to the prototypical SH2, C1, and Rac-GAP domains, β3-chimaerin has a unique N-terminal domain. Studies in cells established that β3-chimaerin has Rac-GAP activity and is responsive to phorbol esters. The enhanced responsiveness of β3-chimaerin for phorbol ester-induced translocation relative to β2-chimaerin suggests differential ligand accessibility to the C1 domain.
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Affiliation(s)
- Lautaro Zubeldia-Brenner
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, IQUIBICEN-CONICET, Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina
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616
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Nordman JC, Phillips WS, Kodama N, Clark SG, Del Negro CA, Kabbani N. Axon targeting of the alpha 7 nicotinic receptor in developing hippocampal neurons by Gprin1 regulates growth. J Neurochem 2014; 129:649-62. [PMID: 24350810 DOI: 10.1111/jnc.12641] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 11/21/2013] [Accepted: 12/15/2013] [Indexed: 02/06/2023]
Abstract
Cholinergic signaling plays an important role in regulating the growth and regeneration of axons in the nervous system. The α7 nicotinic receptor (α7) can drive synaptic development and plasticity in the hippocampus. Here, we show that activation of α7 significantly reduces axon growth in hippocampal neurons by coupling to G protein-regulated inducer of neurite outgrowth 1 (Gprin1), which targets it to the growth cone. Knockdown of Gprin1 expression using RNAi is found sufficient to abolish the localization and calcium signaling of α7 at the growth cone. In addition, an α7/Gprin1 interaction appears intimately linked to a Gαo, growth-associated protein 43, and CDC42 cytoskeletal regulatory pathway within the developing axon. These findings demonstrate that α7 regulates axon growth in hippocampal neurons, thereby likely contributing to synaptic formation in the developing brain.
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Affiliation(s)
- Jacob C Nordman
- Department of Molecular Neuroscience, Krasnow Institute for Advanced Study, George Mason University, Fairfax, Virginia, USA
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617
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Gutierrez-Uzquiza A, Colon-Gonzalez F, Leonard TA, Canagarajah BJ, Wang H, Mayer BJ, Hurley JH, Kazanietz MG. Coordinated activation of the Rac-GAP β2-chimaerin by an atypical proline-rich domain and diacylglycerol. Nat Commun 2013; 4:1849. [PMID: 23673634 PMCID: PMC3700536 DOI: 10.1038/ncomms2834] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Accepted: 04/04/2013] [Indexed: 02/08/2023] Open
Abstract
Chimaerins, a family of GTPase activating proteins (GAPs) for the small G-protein Rac, have been implicated in development, neuritogenesis, and cancer. These Rac-GAPs are regulated by the lipid second messenger diacylglycerol (DAG) generated by tyrosine-kinases such as the epidermal growth factor receptor (EGFR). Here we identify an atypical Pro-rich motif in chimaerins that binds to the adaptor protein Nck1. Unlike most Nck1 partners, chimaerins bind to the third SH3 domain of Nck1. This association is mediated by electrostatic interactions of basic residues within the Pro-rich motif with acidic clusters in the SH3 domain. EGF promotes the binding of β2-chimaerin to Nck1 in the cell periphery in a DAG-dependent manner. Moreover, β2-chimaerin translocation to the plasma membrane and its peripheral association with Rac1 requires Nck1. Our studies underscore a coordinated mechanism for β2-chimaerin activation that involves lipid interactions via the C1 domain and protein-protein interactions via the N-terminal Pro-rich region.
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Affiliation(s)
- Alvaro Gutierrez-Uzquiza
- Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6160, USA
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618
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Ebi H, Costa C, Faber AC, Nishtala M, Kotani H, Juric D, Della Pelle P, Song Y, Yano S, Mino-Kenudson M, Benes CH, Engelman JA. PI3K regulates MEK/ERK signaling in breast cancer via the Rac-GEF, P-Rex1. Proc Natl Acad Sci U S A 2013; 110:21124-9. [PMID: 24327733 DOI: 10.1073/pnas.1314124110] [Citation(s) in RCA: 169] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The PI3K pathway is genetically altered in excess of 70% of breast cancers, largely through PIK3CA mutation and HER2 amplification. Preclinical studies have suggested that these subsets of breast cancers are particularly sensitive to PI3K inhibitors; however, the reasons for this heightened sensitivity are mainly unknown. We investigated the signaling effects of PI3K inhibition in PIK3CA mutant and HER2 amplified breast cancers using PI3K inhibitors currently in clinical trials. Unexpectedly, we found that in PIK3CA mutant and HER2 amplified breast cancers sensitive to PI3K inhibitors, PI3K inhibition led to a rapid suppression of Rac1/p21-activated kinase (PAK)/protein kinase C-RAF (C-RAF)/ protein kinase MEK (MEK)/ERK signaling that did not involve RAS. Furthermore, PI3K inhibition led to an ERK-dependent up-regulation of the proapoptotic protein, BIM, followed by induction of apoptosis. Expression of a constitutively active form of Rac1 in these breast cancer models blocked PI3Ki-induced down-regulation of ERK phosphorylation, apoptosis, and mitigated PI3K inhibitor sensitivity in vivo. In contrast, protein kinase AKT inhibitors failed to block MEK/ERK signaling, did not up-regulate BIM, and failed to induce apoptosis. Finally, we identified phosphatidylinositol 3,4,5-trisphosphate-dependent Rac exchanger 1 (P-Rex1) as the PI(3,4,5)P3-dependent guanine exchange factor for Rac1 responsible for regulation of the Rac1/C-RAF/MEK/ERK pathway in these cells. The expression level of P-Rex1 correlates with sensitivity to PI3K inhibitors in these breast cancer cell lines. Thus, PI3K inhibitors have enhanced activity in PIK3CA mutant and HER2 amplified breast cancers in which PI3K inhibition down-regulates both the AKT and Rac1/ERK pathways. In addition, P-Rex1 may serve as a biomarker to predict response to single-agent PI3K inhibitors within this subset of breast cancers.
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619
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Clark C, Austen O, Poparic I, Guthrie S. α2-Chimaerin regulates a key axon guidance transition during development of the oculomotor projection. J Neurosci 2013; 33:16540-51. [PMID: 24133258 DOI: 10.1523/JNEUROSCI.1869-13.2013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The ocular motor system consists of three nerves which innervate six muscles to control eye movements. In humans, defective development of this system leads to eye movement disorders, such as Duane Retraction Syndrome, which can result from mutations in the α2-chimaerin signaling molecule. We have used the zebrafish to model the role of α2-chimaerin during development of the ocular motor system. We first mapped ocular motor spatiotemporal development, which occurs between 24 and 72 h postfertilization (hpf), with the oculomotor nerve following an invariant sequence of growth and branching to its muscle targets. We identified 52 hpf as a key axon guidance "transition," when oculomotor axons reach the orbit and select their muscle targets. Live imaging and quantitation showed that, at 52 hpf, axons undergo a switch in behavior, with striking changes in the dynamics of filopodia. We tested the role of α2-chimaerin in this guidance process and found that axons expressing gain-of-function α2-chimaerin isoforms failed to undergo the 52 hpf transition in filopodial dynamics, leading to axon stalling. α2-chimaerin loss of function led to ecotopic and misguided branching and hypoplasia of oculomotor axons; embryos had defective eye movements as measured by the optokinetic reflex. Manipulation of chimaerin signaling in oculomotor neurons in vitro led to changes in microtubule stability. These findings demonstrate that a correct level of α2-chimaerin signaling is required for key oculomotor axon guidance decisions, and provide a zebrafish model for Duane Retraction Syndrome.
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620
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Dai X, Iwasaki H, Watanabe M, Okabe S. Dlx1 transcription factor regulates dendritic growth and postsynaptic differentiation through inhibition of neuropilin-2 and PAK3 expression. Eur J Neurosci 2013; 39:531-47. [DOI: 10.1111/ejn.12413] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 10/02/2013] [Accepted: 10/07/2013] [Indexed: 11/28/2022]
Affiliation(s)
- Xiaojing Dai
- Department of Cellular Neurobiology; Graduate School of Medicine; The University of Tokyo; Tokyo Japan
| | - Hirohide Iwasaki
- Department of Cellular Neurobiology; Graduate School of Medicine; The University of Tokyo; Tokyo Japan
| | - Masahiko Watanabe
- Department of Anatomy; Hokkaido University School of Medicine; Sapporo Japan
| | - Shigeo Okabe
- Department of Cellular Neurobiology; Graduate School of Medicine; The University of Tokyo; Tokyo Japan
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621
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Sun LO, Jiang Z, Rivlin-Etzion M, Hand R, Brady CM, Matsuoka RL, Yau KW, Feller MB, Kolodkin AL. On and off retinal circuit assembly by divergent molecular mechanisms. Science 2013; 342:1241974. [PMID: 24179230 DOI: 10.1126/science.1241974] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Direction-selective responses to motion can be to the onset (On) or cessation (Off) of illumination. Here, we show that the transmembrane protein semaphorin 6A and its receptor plexin A2 are critical for achieving radially symmetric arborization of On starburst amacrine cell (SAC) dendrites and normal SAC stratification in the mouse retina. Plexin A2 is expressed in both On and Off SACs; however, semaphorin 6A is expressed in On SACs. Specific On-Off bistratified direction-selective ganglion cells in semaphorin 6A(-/-) mutants exhibit decreased tuning of On directional motion responses. These results correlate the elaboration of symmetric SAC dendritic morphology and asymmetric responses to motion, shedding light on the development of visual pathways that use the same cell types for divergent outputs.
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Affiliation(s)
- Lu O Sun
- Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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622
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Wang Y, Zhou L, Li Z, Li W, Gui J. Apolipoprotein C1 regulates epiboly during gastrulation in zebrafish. Sci China Life Sci 2013; 56:975-84. [PMID: 24203452 DOI: 10.1007/s11427-013-4563-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Accepted: 10/09/2013] [Indexed: 11/28/2022]
Abstract
Apolipoprotein C1 (Apoc1) is associated with lipoprotein metabolism, but its physiological role during embryogenesis is largely unknown. We reveal a new function of Apoc1b, a transcript isoform of Apoc1, in epiboly during zebrafish gastrulation. Apoc1b is expressed in yolk syncytial layers and in deep cells of the ventral and lateral region of the embryos. It displays a radial gradient with high levels in the interior layer and low levels in the superficial layer. Knockdown of Apoc1b by injecting antisense morpholino (MO) caused the epiboly arrest in deep cells. Moreover, we show that the radial intercalation and the radial gradient distribution of E-cadherin are disrupted both in Apoc1b knockdown and overexpressed embryos. Therefore, Apoc1b controls epiboly via E-cadherin-mediated radial intercalation in a gradient-dependent manner.
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Affiliation(s)
- Yang Wang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
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623
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Lewis TL, Courchet J, Polleux F. Cell biology in neuroscience: Cellular and molecular mechanisms underlying axon formation, growth, and branching. ACTA ACUST UNITED AC 2013; 202:837-48. [PMID: 24043699 PMCID: PMC3776347 DOI: 10.1083/jcb.201305098] [Citation(s) in RCA: 114] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Proper brain wiring during development is pivotal for adult brain function. Neurons display a high degree of polarization both morphologically and functionally, and this polarization requires the segregation of mRNA, proteins, and lipids into the axonal or somatodendritic domains. Recent discoveries have provided insight into many aspects of the cell biology of axonal development including axon specification during neuronal polarization, axon growth, and terminal axon branching during synaptogenesis.
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Affiliation(s)
- Tommy L Lewis
- The Scripps Research Institute, Dorris Neuroscience Center, Department of Molecular and Cellular Neuroscience, La Jolla, CA 92037
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624
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Chai S, Qian Y, Tang J, Liang Z, Zhang M, Si J, Li X, Huang W, Xu R, Wang K. RETRACTED: Ca(2+)/calmodulin-dependent protein kinase IIγ, a critical mediator of the NF-κB network, is a novel therapeutic target in non-small cell lung cancer. Cancer Lett 2014; 344:119-28. [PMID: 24189456 DOI: 10.1016/j.canlet.2013.10.022] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 10/22/2013] [Accepted: 10/23/2013] [Indexed: 12/13/2022]
Abstract
This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).
This article has been regretfully retracted at the request of the authors due to mistakes which occurred during the figure preparation. Although the authors published a corrigendum about these mistakes (Cancer Lett. 2016 Aug 1. pii: S0304-3835(16)30443-8), they now feel that it is more appropriate to retract the paper to keep their research at a high standard. All authors have agreed to this decision and apologize for any inconvenience caused by retraction of this article.
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625
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Cook DR, Rossman KL, Der CJ. Rho guanine nucleotide exchange factors: regulators of Rho GTPase activity in development and disease. Oncogene 2013; 33:4021-35. [PMID: 24037532 DOI: 10.1038/onc.2013.362] [Citation(s) in RCA: 286] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 06/25/2013] [Accepted: 06/26/2013] [Indexed: 12/16/2022]
Abstract
The aberrant activity of Ras homologous (Rho) family small GTPases (20 human members) has been implicated in cancer and other human diseases. However, in contrast to the direct mutational activation of Ras found in cancer and developmental disorders, Rho GTPases are activated most commonly in disease by indirect mechanisms. One prevalent mechanism involves aberrant Rho activation via the deregulated expression and/or activity of Rho family guanine nucleotide exchange factors (RhoGEFs). RhoGEFs promote formation of the active GTP-bound state of Rho GTPases. The largest family of RhoGEFs is comprised of the Dbl family RhoGEFs with 70 human members. The multitude of RhoGEFs that activate a single Rho GTPase reflects the very specific role of each RhoGEF in controlling distinct signaling mechanisms involved in Rho activation. In this review, we summarize the role of Dbl RhoGEFs in development and disease, with a focus on Ect2 (epithelial cell transforming squence 2), Tiam1 (T-cell lymphoma invasion and metastasis 1), Vav and P-Rex1/2 (PtdIns(3,4,5)P3 (phosphatidylinositol (3,4,5)-triphosphate)-dependent Rac exchanger).
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Affiliation(s)
- D R Cook
- Division of Chemical Biology and Medicinal Chemistry, University of North Carolina at Chapel Hill, Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA
| | - K L Rossman
- 1] Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA [2] Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA
| | - C J Der
- 1] Division of Chemical Biology and Medicinal Chemistry, University of North Carolina at Chapel Hill, Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA [2] Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA [3] Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA
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626
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Suzuki A, Mimaki S, Yamane Y, Kawase A, Matsushima K, Suzuki M, Goto K, Sugano S, Esumi H, Suzuki Y, Tsuchihara K. Identification and characterization of cancer mutations in Japanese lung adenocarcinoma without sequencing of normal tissue counterparts. PLoS One 2013; 8:e73484. [PMID: 24069199 PMCID: PMC3772023 DOI: 10.1371/journal.pone.0073484] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 07/19/2013] [Indexed: 01/21/2023] Open
Abstract
We analyzed whole-exome sequencing data from 97 Japanese lung adenocarcinoma patients and identified several putative cancer-related genes and pathways. Particularly, we observed that cancer-related mutation patterns were significantly different between different ethnic groups. As previously reported, mutations in the EGFR gene were characteristic to Japanese, while those in the KRAS gene were more frequent in Caucasians. Furthermore, during the course of this analysis, we found that cancer-specific somatic mutations can be detected without sequencing normal tissue counterparts. 64% of the germline variants could be excluded using a total of 217 external Japanese exome datasets. We also show that a similar approach may be used for other three ethnic groups, although the discriminative power depends on the ethnic group. We demonstrate that the ATM gene and the PAPPA2 gene could be identified as cancer prognosis related genes. By bypassing the sequencing of normal tissue counterparts, this approach provides a useful means of not only reducing the time and cost of sequencing but also analyzing archive samples, for which normal tissue counterparts are not available.
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Affiliation(s)
- Ayako Suzuki
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba, Japan
| | - Sachiyo Mimaki
- Division of Translational Research, Research Center for Innovative Oncology, National Cancer Center Hospital East, Chiba, Japan
| | - Yuki Yamane
- Thoracic Oncology Division, National Cancer Center Hospital East, Chiba, Japan
| | - Akikazu Kawase
- Thoracic Oncology Division, National Cancer Center Hospital East, Chiba, Japan
| | - Koutatsu Matsushima
- Division of Translational Research, Research Center for Innovative Oncology, National Cancer Center Hospital East, Chiba, Japan
| | - Makito Suzuki
- Division of Translational Research, Research Center for Innovative Oncology, National Cancer Center Hospital East, Chiba, Japan
| | - Koichi Goto
- Thoracic Oncology Division, National Cancer Center Hospital East, Chiba, Japan
| | - Sumio Sugano
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba, Japan
| | - Hiroyasu Esumi
- Division of Translational Research, Research Center for Innovative Oncology, National Cancer Center Hospital East, Chiba, Japan
| | - Yutaka Suzuki
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba, Japan
- * E-mail:
| | - Katsuya Tsuchihara
- Division of Translational Research, Research Center for Innovative Oncology, National Cancer Center Hospital East, Chiba, Japan
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627
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Chen K, Navin NE, Wang Y, Schmidt HK, Wallis JW, Niu B, Fan X, Zhao H, McLellan MD, Hoadley KA, Mardis ER, Ley TJ, Perou CM, Wilson RK, Ding L. BreakTrans: uncovering the genomic architecture of gene fusions. Genome Biol 2013; 14:R87. [PMID: 23972288 PMCID: PMC4054677 DOI: 10.1186/gb-2013-14-8-r87] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 08/23/2013] [Indexed: 01/18/2023] Open
Abstract
Producing gene fusions through genomic structural rearrangements is a major mechanism for tumor evolution. Therefore, accurately detecting gene fusions and the originating rearrangements is of great importance for personalized cancer diagnosis and targeted therapy. We present a tool, BreakTrans, that systematically maps predicted gene fusions to structural rearrangements. Thus, BreakTrans not only validates both types of predictions, but also provides mechanistic interpretations. BreakTrans effectively validates known fusions and discovers novel events in a breast cancer cell line. Applying BreakTrans to 43 breast cancer samples in The Cancer Genome Atlas identifies 90 genomically validated gene fusions. BreakTrans is available at http://bioinformatics.mdanderson.org/main/BreakTrans.
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628
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Tsygankova OM, Wang H, Meinkoth JL. Tumor cell migration and invasion are enhanced by depletion of Rap1 GTPase-activating protein (Rap1GAP). J Biol Chem 2013; 288:24636-46. [PMID: 23864657 DOI: 10.1074/jbc.m113.464594] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The functional significance of the widespread down-regulation of Rap1 GTPase-activating protein (Rap1GAP), a negative regulator of Rap activity, in human tumors is unknown. Here we show that human colon cancer cells depleted of Rap1GAP are endowed with more aggressive migratory and invasive properties. Silencing Rap1GAP enhanced the migration of confluent and single cells. In the latter, migration distance, velocity, and directionality were increased. Enhanced migration was a consequence of increased endogenous Rap activity as silencing Rap expression selectively abolished the migration of Rap1GAP-depleted cells. ROCK-mediated cell contractility was suppressed in Rap1GAP-depleted cells, which exhibited a spindle-shaped morphology and abundant membrane protrusions. Tumor cells can switch between Rho/ROCK-mediated contractility-based migration and Rac1-mediated mesenchymal motility. Strikingly, the migration of Rap1GAP-depleted, but not control cells required Rac1 activity, suggesting that loss of Rap1GAP alters migratory mechanisms. Inhibition of Rac1 activity restored membrane blebbing and increased ROCK activity in Rap1GAP-depleted cells, suggesting that Rac1 contributes to the suppression of contractility. Collectively, these findings identify Rap1GAP as a critical regulator of aggressive tumor cell behavior and suggest that the level of Rap1GAP expression influences the migratory mechanisms that are operative in tumor cells.
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Affiliation(s)
- Oxana M Tsygankova
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6061, USA
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629
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Abstract
The Rac inhibitor EHop-016 was developed as a compound with the potential to inhibit cancer metastasis. Inhibition of the first step of metastasis, migration, is an important strategy for metastasis prevention. The small GTPase Rac acts as a pivotal binary switch that is turned "on" by guanine nucleotide exchange factors (GEFs) via a myriad of cell surface receptors, to regulate cancer cell migration, survival, and proliferation. Unlike the related GTPase Ras, Racs are not usually mutated, but overexpressed or overactivated in cancer. Therefore, a rational Rac inhibitor should block the activation of Rac by its upstream effectors, GEFs, and the Rac inhibitor NSC23766 was developed using this rationale. However, this compound is ineffective at inhibiting the elevated Rac activity of metastatic breast cancer cells. Therefore, a panel of small molecule compounds were derived from NSC23766 and screened for Rac activity inhibition in metastatic cancer cells. EHop-016 was identified as a compound that blocks the interaction of Rac with the GEF Vav in metastatic human breast cancer cells with an IC50 of ~1μM. At higher concentrations (10μM), EHop-016 inhibits the related Rho GTPase Cdc42, but not Rho, and also reduces cell viability. Moreover, EHop-016 inhibits the activation of the Rac downstream effector p21-activated kinase, extension of motile actin-based structures, and cell migration. Future goals are to develop EHop-016 as a therapeutic to inhibit cancer metastasis, either individually or in combination with current anticancer compounds. The next generation of EHop-016-based Rac inhibitors is also being developed.
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Affiliation(s)
- Suranganie Dharmawardhane
- Department of Biochemistry, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico, USA.
| | - Eliud Hernandez
- Department of Biochemistry, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico, USA
| | - Cornelis Vlaar
- Department of Biochemistry, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico, USA
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630
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Montero JC, Seoane S, Pandiella A. Phosphorylation of P-Rex1 at serine 1169 participates in IGF-1R signaling in breast cancer cells. Cell Signal 2013; 25:2281-9. [PMID: 23899556 DOI: 10.1016/j.cellsig.2013.07.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 07/15/2013] [Accepted: 07/19/2013] [Indexed: 11/30/2022]
Abstract
Former reports demonstrated that P-Rex, a Rac guanine nucleotide exchange factor (GEF), participated in signaling upon activation of the ErbB receptor tyrosine kinases (RTKs). Activation of ErbB receptors turned on a phosphorylation/dephosphorylation cycle of P-Rex in which stimulation of serine(1169) phosphorylation played a critical role in the activation of this GEF. This precedent raised the important question of whether this P-Rex1 activation mechanism was restricted to ErbB receptors or could represent a general signaling event shared by several RTKs. To explore that possibility the effect of activation of distinct RTKs on the phosphorylation of P-Rex1 at serine(1169) was analyzed. Here we report that IGF-1 and FGF receptors activate serine(1169) phosphorylation of P-Rex1. P-Rex1 phosphorylation was required for IGF-1-induced up-regulation of Rac activity and cell proliferation. Moreover, IGF-1-induced adhesion was impaired in MCF7 breast cancer cells by knocking down P-Rex1. These results demonstrate that phosphorylation P-Rex1 at S(1169) represents a mechanism of activation of P-Rex1 common to multiple RTKs. We suggest that P-Rex proteins may act as novel and important transducers of pro-oncogenic signals that emanate from RTKs, and could even participate in other biological responses, such as metabolic control, which are not strictly related to the proliferation effects of RTKs.
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Affiliation(s)
- Juan Carlos Montero
- Instituto de Biología Molecular y Celular del Cáncer, CSIC-Universidad de Salamanca, Spain
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631
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Abstract
This article explores new ideas about how the ECM-integrin axis controls normal and malignant breast biology. We discuss the role of integrins in mammary stem cells, and how cell-matrix interactions regulate ductal and alveolar development and function. We also examine the contribution of integrins to tissue disorganisation and metastasis, and how an altered stromal and ECM tumour microenvironment affects the cancer cell niche both within primary tumours and at distant sites. Finally, we mention novel strategies for integrin-directed breast cancer treatment.
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Affiliation(s)
- Marina A Glukhova
- Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
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632
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Maor-Nof M, Yaron A. Neurite pruning and neuronal cell death: spatial regulation of shared destruction programs. Curr Opin Neurobiol 2013; 23:990-6. [PMID: 23871216 DOI: 10.1016/j.conb.2013.06.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 06/11/2013] [Indexed: 12/25/2022]
Abstract
During development, neurons are initially overproduced and excess neurons are eliminated later on by programmed cell death. In a more refined developmental process termed pruning, excess axons and dendritic branches are removed while the cell body remains intact. In mature animals, axons that become disconnected as a result of injury are eliminated through a series of events collectively known as Wallerian degeneration. Recent evidence points to unexpected similarities between these three types of obliterative processes, as they share common regulators. These findings provide new ideas on how cellular destruction programs are spatially regulated in neurons.
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Affiliation(s)
- Maya Maor-Nof
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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633
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Garg R, Caino MC, Kazanietz MG. Regulation of Transcriptional Networks by PKC Isozymes: Identification of c-Rel as a Key Transcription Factor for PKC-Regulated Genes. PLoS One 2013; 8:e67319. [PMID: 23826267 PMCID: PMC3694964 DOI: 10.1371/journal.pone.0067319] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 05/16/2013] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Activation of protein kinase C (PKC), a family of serine-threonine kinases widely implicated in cancer progression, has major impact on gene expression. In a recent genome-wide analysis of prostate cancer cells we identified distinctive gene expression profiles controlled by individual PKC isozymes and highlighted a prominent role for PKCδ in transcriptional activation. PRINCIPAL FINDINGS Here we carried out a thorough bioinformatics analysis to dissect transcriptional networks controlled by PKCα, PKCδ, and PKCε, the main diacylglycerol/phorbol ester PKCs expressed in prostate cancer cells. Despite the remarkable differences in the patterns of transcriptional responsive elements (REs) regulated by each PKC, we found that c-Rel represents the most frequent RE in promoters regulated by all three PKCs. In addition, promoters of PKCδ-regulated genes were particularly enriched with REs for CREB, NF-E2, RREB, SRF, Oct-1, Evi-1, and NF-κB. Most notably, by using transcription factor-specific RNAi we were able to identify subsets of PKCδ-regulated genes modulated by c-Rel and CREB. Furthermore, PKCδ-regulated genes condensed under the c-Rel transcriptional regulation display significant functional interconnections with biological processes such as angiogenesis, inflammatory response, and cell motility. CONCLUSION/SIGNIFICANCE Our study identified candidate transcription factors in the promoters of PKC regulated genes, in particular c-Rel was found as a key transcription factor in the control of PKCδ-regulated genes. The deconvolution of PKC-regulated transcriptional networks and their nodes may greatly help in the identification of PKC effectors and have significant therapeutics implications.
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Affiliation(s)
- Rachana Garg
- Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - M. Cecilia Caino
- Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Marcelo G. Kazanietz
- Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
- * E-mail:
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634
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Hanson SJ, Stelzer CP, Welch DBM, Logsdon JM. Comparative transcriptome analysis of obligately asexual and cyclically sexual rotifers reveals genes with putative functions in sexual reproduction, dormancy, and asexual egg production. BMC Genomics 2013; 14:412. [PMID: 23782598 PMCID: PMC3701536 DOI: 10.1186/1471-2164-14-412] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2013] [Accepted: 05/31/2013] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Sexual reproduction is a widely studied biological process because it is critically important to the genetics, evolution, and ecology of eukaryotes. Despite decades of study on this topic, no comprehensive explanation has been accepted that explains the evolutionary forces underlying its prevalence and persistence in nature. Monogonont rotifers offer a useful system for experimental studies relating to the evolution of sexual reproduction due to their rapid reproductive rate and close relationship to the putatively ancient asexual bdelloid rotifers. However, little is known about the molecular underpinnings of sex in any rotifer species. RESULTS We generated mRNA-seq libraries for obligate parthenogenetic (OP) and cyclical parthenogenetic (CP) strains of the monogonont rotifer, Brachionus calyciflorus, to identify genes specific to both modes of reproduction. Our differential expression analysis identified receptors with putative roles in signaling pathways responsible for the transition from asexual to sexual reproduction. Differential expression of a specific copy of the duplicated cell cycle regulatory gene CDC20 and specific copies of histone H2A suggest that such duplications may underlie the phenotypic plasticity required for reproductive mode switch in monogononts. We further identified differential expression of genes involved in the formation of resting eggs, a process linked exclusively to sex in this species. Finally, we identified transcripts from the bdelloid rotifer Adineta ricciae that have significant sequence similarity to genes with higher expression in CP strains of B. calyciflorus. CONCLUSIONS Our analysis of global gene expression differences between facultatively sexual and exclusively asexual populations of B. calyciflorus provides insights into the molecular nature of sexual reproduction in rotifers. Furthermore, our results offer insight into the evolution of obligate asexuality in bdelloid rotifers and provide indicators important for the use of monogononts as a model system for investigating the evolution of sexual reproduction.
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Affiliation(s)
- Sara J Hanson
- Department of Biology and Interdisciplinary Program in Genetics, University of Iowa, 301 Biology Building, Iowa City, IA 52242, USA
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635
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Abstract
Podocytes play a critical role in maintaining glomerular permselectivity. It has been long recognized that their intricate actin-based structures are tightly associated with their normal function; however, the precise mechanisms by which podocytes form and maintain their complex structure had been poorly understood until the intensive investigations on podocyte biology began in 1998, triggered by the breakthrough discovery of nephrin. This review summarizes the recent discoveries of the molecular mechanisms by which the actin cytoskeleton is regulated in podocytes. A particular focus will be on the role of the Rho-family of small GTPases, represented by RhoA, Rac1, and Cdc42. Rho-GTPases are known for their versatile cellular functions, most importantly for the actin regulatory roles. We will also discuss the potential roles of the 3 groups of proteins known to regulate Rho-GTPases, namely GTPase-activating proteins, guanine nucleotide exchange factors, and guanine nucleotide dissociation inhibitors.
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Affiliation(s)
- Flaviana Mouawad
- Department of Medicine, McGill University Health Centre, Montreal, QC H3A 2B4, Canada
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636
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Abstract
P-Rex proteins are Rho/Rac guanine nucleotide exchange factors that participate in the regulation of several cancer-related cellular functions such as proliferation, motility, and invasion. Expectedly, a significant portion of these actions of P-Rex proteins must be related to their Rac regulatory properties. In addition, P-Rex proteins control signaling by the phosphoinositide 3-kinase (PI3K) route by interacting with PTEN and mTOR. The interaction with PTEN inhibits its phosphatase activity, leading to AKT activation. The interaction with mTOR may be important in nutrient-stimulated Rac activation and migration. In humans, several studies have implicated P-Rex proteins in the pathophysiology of various neoplasias. Thus, overexpression of P-Rex proteins has been linked to poor patient outcome in breast cancer and may facilitate metastatic dissemination of prostate cancer cells. In addition, whole-genome sequencing described P-Rex2 as a significantly mutated gene in melanoma. Furthermore, expression in melanocytes of mutated forms of P-Rex2 found in patients with melanoma showed the protumorigenic role of these P-Rex mutations in melanoma genesis. These findings open interesting opportunities for P-Rex targeting in cancer. Moreover, the implication of P-Rex partner proteins such as Rac, mTOR, or PTEN in cancer has opened the possibility of acting on P-Rex to restrict protumorigenic signaling through these pathways.
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Affiliation(s)
- Atanasio Pandiella
- Instituto de Biología Molecular y Celular del Cáncer, Centro de Investigación del Cáncer, CSIC-Universidad de Salamanca, Spain.
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637
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Abstract
Cell adhesion to the extracellular matrix elicits a temporal reorganization of the actin cytoskeleton that is regulated first by Rac1 and later by RhoA. The signaling mechanisms controlling late stage RhoA activation are incompletely understood. Net1A is a RhoA/RhoB-specific guanine nucleotide exchange factor that is required for cancer cell motility. The ability of Net1A to stimulate RhoA activation is negatively regulated by nuclear sequestration. However, mechanisms controlling the plasma membrane localization of Net1A had not previously been reported. Recently we have shown that Rac1 activation stimulates plasma membrane relocalization and activation of Net1A. Net1A relocalization is independent of its catalytic activity and does not require its C-terminal pleckstrin homology or PDZ interacting domains. Rac1 activation during cell adhesion stimulates a transient relocalization of Net1A that is terminated by proteasomal degradation of Net1A. Importantly, plasma membrane localization of Net1A is required for efficient myosin light chain phosphorylation, focal adhesion maturation, and cell spreading. These data show for the first time a physiological mechanism controlling Net1A relocalization from the nucleus. They also demonstrate a previously unrecognized role for Net1A in controlling actomyosin contractility and focal adhesion dynamics during cell adhesion.
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Affiliation(s)
- Heather S Carr
- Department of Integrative Biology and Pharmacology; University of Texas Health Science Center at Houston; Houston, TX USA
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638
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Teves ME, Zhang Z, Costanzo RM, Henderson SC, Corwin FD, Zweit J, Sundaresan G, Subler M, Salloum FN, Rubin BK, Strauss JF. Sperm-associated antigen-17 gene is essential for motile cilia function and neonatal survival. Am J Respir Cell Mol Biol 2013; 48:765-72. [PMID: 23418344 PMCID: PMC3727877 DOI: 10.1165/rcmb.2012-0362oc] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Accepted: 01/16/2013] [Indexed: 11/24/2022] Open
Abstract
Primary ciliary dyskinesia (PCD), resulting from defects in cilia assembly or motility, is caused by mutations in a number of genes encoding axonemal proteins. PCD phenotypes are variable, and include recurrent respiratory tract infections, bronchiectasis, hydrocephaly, situs inversus, and male infertility. We generated knockout mice for the sperm-associated antigen-17 (Spag17) gene, which encodes a central pair (CP) protein present in the axonemes of cells with "9 + 2" motile cilia or flagella. The targeting of Spag17 resulted in a severe phenotype characterized by immotile nasal and tracheal cilia, reduced clearance of nasal mucus, profound respiratory distress associated with lung fluid accumulation and disruption of the alveolar epithelium, cerebral ventricular expansion consistent with emerging hydrocephalus, failure to suckle, and neonatal demise within 12 hours of birth. Ultrastructural analysis revealed the loss of one CP microtubule in approximately one quarter of tracheal cilia axonemes, an absence of a C1 microtubule projection, and other less frequent CP structural abnormalities. SPAG6 and SPAG16 (CP proteins that interact with SPAG17) were increased in tracheal tissue from SPAG17-deficient mice. We conclude that Spag17 plays a critical role in the function and structure of motile cilia, and that neonatal lethality is likely explained by impaired airway mucociliary clearance.
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Affiliation(s)
| | - Zhibing Zhang
- Department of Obstetrics and Gynecology
- Department of Biochemistry and Molecular Biology
| | | | | | | | - Jamal Zweit
- Department of Biochemistry and Molecular Biology
- Department of Radiology
| | | | | | - Fadi N. Salloum
- Pauley Heart Center, Division of Cardiology, Department of Internal Medicine, and
| | - Bruce K. Rubin
- Department of Physiology and Biophysics
- Department of Pediatrics, Virginia Commonwealth University, Richmond, Virginia
| | - Jerome F. Strauss
- Department of Obstetrics and Gynecology
- Department of Biochemistry and Molecular Biology
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639
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Dipaolo BC, Davidovich N, Kazanietz MG, Margulies SS. Rac1 pathway mediates stretch response in pulmonary alveolar epithelial cells. Am J Physiol Lung Cell Mol Physiol 2013; 305:L141-53. [PMID: 23686855 DOI: 10.1152/ajplung.00298.2012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Alveolar epithelial cells (AECs) maintain the pulmonary blood-gas barrier integrity with gasketlike intercellular tight junctions (TJ) that are anchored internally to the actin cytoskeleton. We have previously shown that AEC monolayers stretched cyclically and equibiaxially undergo rapid magnitude- and frequency-dependent actin cytoskeletal remodeling to form perijunctional actin rings (PJARs). In this work, we show that even 10 min of stretch induced increases in the phosphorylation of Akt and LIM kinase (LIMK) and decreases in cofilin phosphorylation, suggesting that the Rac1/Akt pathway is involved in these stretch-mediated changes. We confirmed that Rac1 inhibitors wortmannin or EHT-1864 decrease stretch-stimulated Akt and LIMK phosphorylation and that Rac1 agonists PIP3 or PDGF increase phosphorylation of these proteins in unstretched cells. We also confirmed that Rac1 pathway inhibition during stretch modulated stretch-induced changes in occludin content and monolayer permeability, actin remodeling and PJAR formation, and cell death. As further validation, overexpression of Rac GTPase-activating protein β2-chimerin also preserved monolayer barrier properties in stretched monolayers. In summary, our data suggest that constitutive activity of Rac1, which is necessary for stretch-induced activation of the Rac1 downstream proteins, mediates stretch-induced increases in permeability and PJAR formation.
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Affiliation(s)
- Brian C Dipaolo
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
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640
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Degenhardt K, Singh MK, Aghajanian H, Massera D, Wang Q, Li J, Li L, Choi C, Yzaguirre AD, Francey LJ, Gallant E, Krantz ID, Gruber PJ, Epstein JA. Semaphorin 3d signaling defects are associated with anomalous pulmonary venous connections. Nat Med 2013; 19:760-5. [PMID: 23685842 DOI: 10.1038/nm.3185] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Accepted: 04/04/2013] [Indexed: 01/22/2023]
Abstract
Total anomalous pulmonary venous connection (TAPVC) is a potentially lethal congenital disorder that occurs when the pulmonary veins do not connect normally to the left atrium, allowing mixing of pulmonary and systemic blood. In contrast to the extensive knowledge of arterial vascular patterning, little is known about the patterning of veins. Here we show that the secreted guidance molecule semaphorin 3d (Sema3d) is crucial for the normal patterning of pulmonary veins. Prevailing models suggest that TAPVC occurs when the midpharyngeal endothelial strand (MES), the precursor of the common pulmonary vein, does not form at the proper location on the dorsal surface of the embryonic common atrium. However, we found that TAPVC occurs in Sema3d mutant mice despite normal formation of the MES. In these embryos, the maturing pulmonary venous plexus does not anastomose uniquely with the properly formed MES. In the absence of Sema3d, endothelial tubes form in a region that is normally avascular, resulting in aberrant connections. Normally, Sema3d provides a repulsive cue to endothelial cells in this area, establishing a boundary. Sequencing of SEMA3D in individuals with anomalous pulmonary veins identified a phenylalanine-to-leucine substitution that adversely affects SEMA3D function. These results identify Sema3d as a crucial pulmonary venous patterning cue and provide experimental evidence for an alternate developmental model to explain abnormal pulmonary venous connections.
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Affiliation(s)
- Karl Degenhardt
- Department of Pediatrics, Division of Cardiology, Children's Hospital of Philadelphia, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
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641
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Asahara S, Shibutani Y, Teruyama K, Inoue HY, Kawada Y, Etoh H, Matsuda T, Kimura-Koyanagi M, Hashimoto N, Sakahara M, Fujimoto W, Takahashi H, Ueda S, Hosooka T, Satoh T, Inoue H, Matsumoto M, Aiba A, Kasuga M, Kido Y. Ras-related C3 botulinum toxin substrate 1 (RAC1) regulates glucose-stimulated insulin secretion via modulation of F-actin. Diabetologia 2013; 56:1088-97. [PMID: 23412604 PMCID: PMC3622740 DOI: 10.1007/s00125-013-2849-5] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 01/17/2013] [Indexed: 11/03/2022]
Abstract
AIMS/HYPOTHESIS The small G-protein ras-related C3 botulinum toxin substrate 1 (RAC1) plays various roles in mammalian cells, such as in the regulation of cytoskeletal organisation, cell adhesion, migration and morphological changes. The present study examines the effects of RAC1 ablation on pancreatic beta cell function. METHODS Isolated islets from pancreatic beta cell-specific Rac1-knockout (betaRac1(-/-)) mice and RAC1 knockdown INS-1 insulinoma cells treated with small interfering RNA were used to investigate insulin secretion and cytoskeletal organisation in pancreatic beta cells. RESULTS BetaRac1(-/-) mice showed decreased glucose-stimulated insulin secretion, while there were no apparent differences in islet morphology. Isolated islets from the mice had blunted insulin secretion in response to high glucose levels. In RAC1 knockdown INS-1 cells, insulin secretion was also decreased in response to high glucose levels, consistent with the phenotype of betaRac1(-/-) mice. Even under high glucose levels, RAC1 knockdown INS-1 cells remained intact with F-actin, which inhibits the recruitment of the insulin granules, resulting in an inhibition of insulin secretion. CONCLUSIONS/INTERPRETATION In RAC1-deficient pancreatic beta cells, F-actin acts as a barrier for insulin granules and reduces glucose-stimulated insulin secretion.
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Affiliation(s)
- S. Asahara
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Y. Shibutani
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - K. Teruyama
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
| | - H. Y. Inoue
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
| | - Y. Kawada
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
| | - H. Etoh
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
| | - T. Matsuda
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - M. Kimura-Koyanagi
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - N. Hashimoto
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - M. Sakahara
- Cancer Institute, Japanese Foundation of Cancer Research, Tokyo, Japan
| | - W. Fujimoto
- Division of Cellular and Molecular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - H. Takahashi
- Division of Cellular and Molecular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - S. Ueda
- Kobe University Graduate School of Agricultural Science, Kobe, Japan
| | - T. Hosooka
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - T. Satoh
- Division of Molecular Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - H. Inoue
- Department of Physiology and Metabolism, Brain/Liver Interface Medicine Research Center, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan
| | - M. Matsumoto
- Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - A. Aiba
- Laboratory of Animal Resources, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, Tokyo, Japan
| | - M. Kasuga
- Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Y. Kido
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
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642
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Laurin M, Huber J, Pelletier A, Houalla T, Park M, Fukui Y, Haibe-Kains B, Muller WJ, Côté JF. Rac-specific guanine nucleotide exchange factor DOCK1 is a critical regulator of HER2-mediated breast cancer metastasis. Proc Natl Acad Sci U S A 2013; 110:7434-9. [PMID: 23592719 DOI: 10.1073/pnas.1213050110] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Progression of solid tumors to the metastatic stage is accountable for the majority of cancer-related deaths. Further understanding of the molecular mechanisms governing metastasis is essential for the development of antimetastatic regimens. Here, we aimed to identify Rac activators that could promote metastasis downstream of human epithelial growth factor receptor 2 (HER2). We investigated if Dedicator of Cytokinesis 1 (DOCK1), based on its evolutionarily conserved role in receptor tyrosine kinases (RTKs)-mediated Rac activation and cell invasion, could be a regulator of metastasis. We report that high expression of DOCK1 in HER2(+) and basal breast cancer subtypes inversely correlates with human patients' survival. Mechanistically, DOCK1 interacts with HER2 and promotes HER2-induced Rac activation and cell migration. To gain further insight, we developed a HER2 breast cancer mouse model with mammary-gland-specific inactivation of DOCK1. In this in vivo model, a significant decrease in tumor growth and metastasis in lungs was found in animals where DOCK1 is inactivated. Furthermore, we found that DOCK1 is required for maximal activation of two HER2 effectors, c-JUN and STAT3. Using an unbiased gene profiling approach, we identified a mammary tumor DOCK1-associated gene signature enriched for genes implicated in response to IFN type I. This analysis revealed a unique set of genes, including Receptor Transporter Protein 4 (RTP4) and STAT1, for which the expression levels can be used to independently predict breast cancer outcome in HER2(+) patients. Our work demonstrates DOCK1-Rac signaling as an HER2 effector pathway essential for HER2-mediated breast cancer progression to metastasis and offers a therapeutic opportunity to limit the spread of metastatic breast cancers.
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643
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Li X, Zhou Q, Sunkara M, Kutys ML, Wu Z, Rychahou P, Morris AJ, Zhu H, Evers BM, Huang C. Ubiquitylation of phosphatidylinositol 4-phosphate 5-kinase type I γ by HECTD1 regulates focal adhesion dynamics and cell migration. J Cell Sci 2013; 126:2617-28. [PMID: 23572508 DOI: 10.1242/jcs.117044] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Phosphatidylinositol 4-phosphate 5-kinase type I γ (PIPKIγ90) binds talin and localizes at focal adhesions (FAs). Phosphatidylinositol (4,5)-bisphosphate (PIP2) generated by PIPKIγ90 is essential for FA formation and cell migration. On the other hand, PIPKIγ90 and the β-integrin tail compete for overlapping binding sites on talin. Enhanced PIPKIγ90-talin interaction suppresses talin binding to the β-integrin. It is unknown how PIPKIγ90 is removed from the PIPKIγ90-talin complex after on-site PIP2 production during cell migration. Here we show that PIPKIγ90 is a substrate for HECTD1, an E3 ubiquitin ligase regulating cell migration. HECTD1 ubiquitinated PIPKIγ90 at lysine 97 and resulted in PIPKIγ90 degradation. Expression of the mutant PIPKIγ90(K97R) enhanced PIP2 and PIP3 production, inhibited FA assembly and disassembly and inhibited cancer cell migration, invasion and metastasis. Interestingly, mutation at tryptophan 647 abolished the inhibition of PIPKIγ90(K97R) on FA dynamics and partially rescued cancer cell migration and invasion. Thus, cycling PIPKIγ90 ubiquitylation by HECTD1 and consequent degradation remove PIPKIγ90 from talin after on-site PIP2 production, providing an essential regulatory mechanism for FA dynamics and cell migration.
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Affiliation(s)
- Xiang Li
- Markey Cancer Center, University of Kentucky, Lexington, KY 40506, USA
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644
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Abstract
Inhibitors of Apoptosis Proteins (IAPs) are well-studied E3 ubiquitin ligases predominantly known for regulation of apoptosis. We uncovered that IAPs can function as a direct E3 ubiquitin ligase of RhoGTPase Rac1. cIAP1 and XIAP directly conjugate polyubiquitin chains to Lysine 147 of activated Rac1 and target it for proteasomal degradation. Consistently, loss of these IAPs by various strategies led to stabilization of Rac1 and mesenchymal mode of migration in tumor cells. IAPs also regulate Rac1 degradation upon RhoGDI1 depletion and CNF1 toxin treatment. Our observations revealed an evolutionarily conserved role of IAPs in regulating Rac1 stability shedding light on to the mechanisms behind ubiquitination–dependent inactivation of Rac1 signaling.
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Affiliation(s)
- Tripat Kaur Oberoi-Khanuja
- Emmy Noether Group of the DFG, Institute of Biochemistry II, Goethe University Medical School; Frankfurt, Germany
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645
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Abstract
Small GTPase proteins regulate cytoskeletal dynamics to orchestrate diverse cellular functions in organismal physiology, development and disease. The Rho GTPase family member Rac1 is central to actin-driven processes in a number of cell types, particularly platelets, where Rac1 serves as an essential mediator of lamellipodia formation and thrombus stability. Despite the importance of Rac1 to platelet function, little is known about how Rac1 activity is regulated in platelets. We recently defined the tyrosine-kinase based signaling cascade that activates mTOR to regulate Rac1 activation downstream of platelet integrin and glycoprotein receptors. We demonstrated a critical role for the mTOR-Rac1 axis in regulating platelet spreading, aggregation and aggregate stability under shear. These studies suggest that in addition to cancer and transplant medicine, intervention of the mTOR system may have implications for hemostatic and thrombotic processes as well as immunotherapies and intravascular stent design.
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Affiliation(s)
- Joseph E Aslan
- Department of Biomedical Engineering, School of Medicine, Oregon Health & Science University, Portland, OR USA.
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646
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Lopez-Haber C, Kazanietz MG. Cucurbitacin I inhibits Rac1 activation in breast cancer cells by a reactive oxygen species-mediated mechanism and independently of Janus tyrosine kinase 2 and P-Rex1. Mol Pharmacol 2013; 83:1141-54. [PMID: 23478800 DOI: 10.1124/mol.112.084293] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The small GTPase Rac1 has been widely implicated in mammary tumorigenesis and metastasis. Previous studies established that stimulation of ErbB receptors in breast cancer cells activates Rac1 and enhances motility via the Rac-guanine nucleotide exchange factor P-Rex1. As the Janus tyrosine kinase 2 (Jak2)/signal transducer and activator of transcription 3 (Stat3) pathway has been shown to be functionally associated with ErbB receptors, we asked if this pathway could mediate P-Rex1/Rac1 activation in response to ErbB ligands. Here we found that the anticancer agent cucurbitacin I, a Jak2 inhibitor, reduced the activation of Rac1 and motility in response to the ErbB3 ligand heregulin in breast cancer cells. However, Rac1 activation was not affected by Jak2 or Stat3 RNA interference, suggesting that the effect of cucurbitacin I occurs through a Jak2-independent mechanism. Cucurbitacin I also failed to affect the activation of P-Rex1 by heregulin. Subsequent analysis revealed that cucurbitacin I strongly activates RhoA and the Rho effector Rho kinase (ROCK) in breast cancer cells and induces the formation of stress fibers. Interestingly, disruption of the RhoA-ROCK pathway prevented the inhibitory effect of cucurbitacin I on Rac1 activation by heregulin. Lastly, we found that RhoA activation by cucurbitacin I is mediated by reactive oxygen species (ROS). The ROS scavenger N-acetyl L-cysteine and the mitochondrial antioxidant Mito-TEMPO rescued the inhibitory effect of cucurbitacin I on Rac1 activation. In conclusion, these results indicate that ErbB-driven Rac1 activation in breast cancer cells proceeds independently of the Jak2 pathway. Moreover, they established that the inhibitory effect of cucurbitacin I on Rac1 activity involves the alteration of the balance between Rho and Rac.
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Affiliation(s)
- Cynthia Lopez-Haber
- Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6160, USA
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647
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Shi Y, Zhang L, Song S, Teves ME, Li H, Wang Z, Hess RA, Jiang G, Zhang Z. The mouse transcription factor-like 5 gene encodes a protein localized in the manchette and centriole of the elongating spermatid. Andrology 2013; 1:431-9. [PMID: 23444080 DOI: 10.1111/j.2047-2927.2013.00069.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 01/05/2013] [Accepted: 01/11/2013] [Indexed: 12/17/2022]
Abstract
Spermiogenesis is the final phase of spermatogenesis. During this process, haploid round spermatids differentiate into spermatozoa, with dramatic morphological changes, including elongation and condensation of the nuclei, and formation of the flagella. Meig1 is one of many genes involved in the regulation of this process. Male mice deficient in MEIG1 are sterile with a severe defect in spermiogenesis, associated with dramatic disruption of the spermatid manchette and failure of flagellogenesis. A yeast two-hybrid screen using full-length MEIG1 as bait identified transcription factor-like 5 protein (TCFL5) as a putative interacting proteins. Interestingly, this protein was also identified as a potential binding partner of SPAG16, another protein essential for spermatogenesis, and also a binding partner of MEIG1. The interaction between TCFL5 and MEIG1 was confirmed in cultured cells over-expressing the two proteins. The mouse Tcfl5 transcript is present only in the testis, and its expression is significantly increased during spermiogenesis. However, little is known about TCFL5 protein and its role in male germ cells. A rabbit polyclonal antibody was generated against the C-terminal region of TCFL5. Mouse TCFL5 protein was expressed in the testis but not in mature spermatozoa. During the first wave of spermatogenesis, TCFL5 expression was dramatically increased at day 30 after birth. In the testis and a mixture of dispersed testicular cells, the protein co-localized with α-tubulin, a manchette marker in early elongating spermatids. The protein also localized in the centrioles of late elongating spermatids. No obvious differences in TCFL5 epitope abundance and localization were observed between wild type and the Meig1-deficient mice. These findings suggest that TCFL5 may play a role upstream of MEIG1 action, and based on putative binding partners and localization is likely to be involved in spermiogenesis and formation of the sperm flagella.
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Affiliation(s)
- Y Shi
- School of Public Health, Wuhan University of Science and Technology, Wuhan, China
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648
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Abstract
Nodal, acting through Prex1 and Rac1, promotes dynamic actin and random motility in endodermal cells during early gastrulation. Embryo morphogenesis is driven by dynamic cell behaviors, including migration, that are coordinated with fate specification and differentiation, but how such coordination is achieved remains poorly understood. During zebrafish gastrulation, endodermal cells sequentially exhibit first random, nonpersistent migration followed by oriented, persistent migration and finally collective migration. Using a novel transgenic line that labels the endodermal actin cytoskeleton, we found that these stage-dependent changes in migratory behavior correlated with changes in actin dynamics. The dynamic actin and random motility exhibited during early gastrulation were dependent on both Nodal and Rac1 signaling. We further identified the Rac-specific guanine nucleotide exchange factor Prex1 as a Nodal target and showed that it mediated Nodal-dependent random motility. Reducing Rac1 activity in endodermal cells caused them to bypass the random migration phase and aberrantly contribute to mesodermal tissues. Together, our results reveal a novel role for Nodal signaling in regulating actin dynamics and migration behavior, which are crucial for endodermal morphogenesis and cell fate decisions.
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Affiliation(s)
- Stephanie Woo
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA.
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Campbell AD, Lawn S, McGarry LC, Welch HC, Ozanne BW, Norman JC. P-Rex1 cooperates with PDGFRβ to drive cellular migration in 3D microenvironments. PLoS One 2013; 8:e53982. [PMID: 23382862 DOI: 10.1371/journal.pone.0053982] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Accepted: 12/05/2012] [Indexed: 01/11/2023] Open
Abstract
Expression of the Rac-guanine nucleotide exchange factor (RacGEF), P-Rex1 is a key determinant of progression to metastasis in a number of human cancers. In accordance with this proposed role in cancer cell invasion and metastasis, we find that ectopic expression of P-Rex1 in an immortalised human fibroblast cell line is sufficient to drive multiple migratory and invasive phenotypes. The invasive phenotype is greatly enhanced by the presence of a gradient of serum or platelet-derived growth factor, and is dependent upon the expression of functional PDGF receptor β. Consistently, the invasiveness of WM852 melanoma cells, which endogenously express P-Rex1 and PDGFRβ, is opposed by siRNA of either of these proteins. Furthermore, the current model of P-Rex1 activation is advanced through demonstration of P-Rex1 and PDGFRβ as components of the same macromolecular complex. These data suggest that P-Rex1 has an influence on physiological migratory processes, such as invasion of cancer cells, both through effects upon classical Rac1-driven motility and a novel association with RTK signalling complexes.
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Carracedo S, Braun U, Leitges M. Expression pattern of protein kinase Cδ during mouse embryogenesis. BMC Dev Biol 2013; 13:2. [PMID: 23305608 PMCID: PMC3552935 DOI: 10.1186/1471-213x-13-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 01/08/2013] [Indexed: 02/02/2023]
Abstract
Background The members of the protein kinase C (PKC) family consist of serine/threonine kinases classified according to their regulatory domain. Those that belong to the novel PKC subfamily, such as PKCδ, are dependent on diacylglycerol but not Calcium when considering their catalytic activity. Although several studies have shown the importance of PKCδ in different cellular events in health and disease, the overall in vivo distribution of this PKC isoform during development is still lacking. Through Lac Z and antibody staining procedures, we show here the in vivo expression of PKCδ during mouse embryogenesis. Results Ganglia were the domains with most prominent expression of PKCδ in most of the stages analysed, although PKCδ could also be detected in heart and somites at earlier stages, and cartilage primordium and skin among other sites in older embryos. Conclusions The strong expression of PKCδ in ganglia during murine development shown in this study suggests a significant role of this isoform as well as redundancy with other PKCs within the nervous system, since PKCδ deficient mice develop normally.
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Affiliation(s)
- Sergio Carracedo
- The Biotechnology Centre of Oslo, University of Oslo, Gaustadalleen 21, Oslo, Norway.
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