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Ambele MA, Dhanraj P, Giles R, Pepper MS. Adipogenesis: A Complex Interplay of Multiple Molecular Determinants and Pathways. Int J Mol Sci 2020; 21:E4283. [PMID: 32560163 PMCID: PMC7349855 DOI: 10.3390/ijms21124283] [Citation(s) in RCA: 160] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 06/07/2020] [Indexed: 11/24/2022] Open
Abstract
The formation of adipocytes during embryogenesis has been largely understudied. However, preadipocytes appear to originate from multipotent mesenchymal stromal/stem cells which migrate from the mesoderm to their anatomical localization. Most studies on adipocyte formation (adipogenesis) have used preadipocytes derived from adult stem/stromal cells. Adipogenesis consists of two phases, namely commitment and terminal differentiation. This review discusses the role of signalling pathways, epigenetic modifiers, and transcription factors in preadipocyte commitment and differentiation into mature adipocytes, as well as limitations in our understanding of these processes. To date, a limited number of transcription factors, genes and signalling pathways have been described to regulate preadipocyte commitment. One reason could be that most studies on adipogenesis have used preadipocytes already committed to the adipogenic lineage, which are therefore not suitable for studying preadipocyte commitment. Conversely, over a dozen molecular players including transcription factors, genes, signalling pathways, epigenetic regulators, and microRNAs have been described to be involved in the differentiation of preadipocytes to adipocytes; however, only peroxisome proliferator-activated receptor gamma has proven to be clinically relevant. A detailed understanding of how the molecular players underpinning adipogenesis relate to adipose tissue function could provide new therapeutic approaches for addressing obesity without compromising adipose tissue function.
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Affiliation(s)
- Melvin A. Ambele
- Department of Immunology, and SAMRC Extramural Unit for Stem Cell Research and Therapy, Institute for Cellular and Molecular Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria 0001, South Africa; (M.A.A.); (P.D.); (R.G.)
- Department of Oral Pathology and Oral Biology, School of Dentistry, Faculty of Health Sciences, University of Pretoria, Pretoria 0001, South Africa
| | - Priyanka Dhanraj
- Department of Immunology, and SAMRC Extramural Unit for Stem Cell Research and Therapy, Institute for Cellular and Molecular Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria 0001, South Africa; (M.A.A.); (P.D.); (R.G.)
| | - Rachel Giles
- Department of Immunology, and SAMRC Extramural Unit for Stem Cell Research and Therapy, Institute for Cellular and Molecular Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria 0001, South Africa; (M.A.A.); (P.D.); (R.G.)
| | - Michael S. Pepper
- Department of Immunology, and SAMRC Extramural Unit for Stem Cell Research and Therapy, Institute for Cellular and Molecular Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria 0001, South Africa; (M.A.A.); (P.D.); (R.G.)
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Yang SM, Park YK, Kim JI, Lee YH, Lee TY, Jang BC. LY3009120, a pan-Raf kinase inhibitor, inhibits adipogenesis of 3T3-L1 cells by controlling the expression and phosphorylation of C/EBP-α, PPAR-γ, STAT‑3, FAS, ACC, perilipin A, and AMPK. Int J Mol Med 2018; 42:3477-3484. [PMID: 30272260 DOI: 10.3892/ijmm.2018.3890] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 09/04/2018] [Indexed: 11/06/2022] Open
Abstract
Excessive preadipocyte differentiation/adipogenesis is closely linked to the development of obesity. LY3009120 is a pan‑Raf kinase inhibitor and is known for its anticancer activities. In the present study, the effect of LY3009120 on 3T3‑L1 cell adipogenesis was investigated. The differentiation of 3T3‑L1 preadipocytes into adipocytes was measured by Oil Red O staining and AdipoRed assay. Changes of cellular protein expression and phosphorylation levels in differentiating 3T3‑L1 preadipocytes in the absence or presence of LY3009120 were determined by western blotting analysis. Cell count assay was used to assess the cytotoxicity of LY3009120 on 3T3‑L1 cells. At 0.3 µM, LY3009120 markedly inhibited lipid accumulation and decreased triglyceride content in differentiating 3T3‑L1 cells. However, it had minimal effect on the elevated expression and phosphorylation of three Raf kinase isoforms (C‑Raf, A‑Raf, and B‑Raf) observed in the cells. LY3009120 reduced not only the expression of CCAAT/enhancer‑binding protein‑α (C/EBP‑α), peroxisome proliferator‑activated receptor‑γ (PPAR‑γ), fatty acid synthase (FAS), acetyl CoA carboxylase (ACC), and perilipin A, but also reduced the phosphorylation of signal transducer and activator of transcription‑3 (STAT‑3) in differentiating 3T3‑L1 cells. LY3009120 also increased the phosphorylation of adenosine 3',5'‑cyclic monophosphate (cAMP)‑activated protein kinase (AMPK), but did not affect the phosphorylation or expression of liver kinase B1 in these cells. In summary, this is the first report, to the best of our knowledge, demonstrating that LY3009120 has an anti‑adipogenic effect on 3T3‑L1 cells, which may be mediated through control of the expression and phosphorylation of C/EBP‑α, PPAR‑γ, STAT‑3, FAS, ACC, perilipin A, and AMPK.
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Affiliation(s)
- Su-Min Yang
- Department of Molecular Medicine, College of Medicine, Keimyung University, Daegu 42601, Republic of Korea
| | - Yu-Kyoung Park
- Department of Molecular Medicine, College of Medicine, Keimyung University, Daegu 42601, Republic of Korea
| | - Jee In Kim
- Department of Molecular Medicine, College of Medicine, Keimyung University, Daegu 42601, Republic of Korea
| | - Yun-Han Lee
- Department of Molecular Medicine, College of Medicine, Keimyung University, Daegu 42601, Republic of Korea
| | - Tae-Yun Lee
- Department of Microbiology, College of Medicine, Yeungnam University, Daegu 42415, Republic of Korea
| | - Byeong-Churl Jang
- Department of Molecular Medicine, College of Medicine, Keimyung University, Daegu 42601, Republic of Korea
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Lacroix JP, Wang B. Prospective Case Series of Cutaneous Adverse Effects Associated With Dabrafenib and Trametinib. J Cutan Med Surg 2016; 21:54-59. [DOI: 10.1177/1203475416670368] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Background: Dabrafenib, a novel selective small-molecule inhibitor of BRAF, has been shown to increase overall survival in patients with unresectable metastatic melanoma harboring the BRAF V600E mutation. The development of resistance has led to combination therapy with selective MEK inhibitor trametinib. Compared with vemurafenib, dabrafenib is a more recent BRAF inhibitor approved by the Food and Drug Administration in May 2013 for metastatic melanoma; fewer data are available in the current literature regarding cutaneous toxicity. Objectives: We sought to present additional cutaneous side effects of dabrafenib and trametinib and follow their evolution and management. Methods: We carried out a prospective study of 14 patients treated with dabrafenib alone or with trametinib. Patients were followed every 4 weeks, and we collected detailed cutaneous symptoms, photos, and biopsy specimens. Results: All patients presented with at least 1 adverse skin reaction. The mean duration of treatment was 24 weeks. The most common adverse effect was papillomas (7/14), followed by palmoplantar hyperkeratosis (5/14), alopecia (5/14), and seborrheic dermatitis-like eruption (2/14). Three patients who received trametinib developed an acneiform eruption (3/5). One patient developed a keratoacanthoma-like squamous cell carcinoma. Side effects presented as early as 2 weeks after starting therapy, with a mean time of onset of 9 weeks. Conclusion: Selective BRAF inhibitor dabrafenib and MEK inhibitor trametinib are associated with multiple skin adverse effects. Given their recent approval and the potential for malignant lesions to develop on treatment, awareness of potential adverse effects and their management is necessary.
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Affiliation(s)
| | - Beatrice Wang
- McGill University, Division Dermatology, Montréal, QC, Canada
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STAGSTED JAN. Journey beyond immunology. Regulation of receptor internalization by major histocompatibility complex class I (MHC-I) and effect of peptides derived from MHC-I. APMIS 2011. [DOI: 10.1111/j.1600-0463.1998.tb05657.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Abstract
This paper reviews the current understanding of the vitamin D-induced differentiation of neoplastic cells, which results in the generation of cells that acquire near-normal, mature phenotype. Examples of the criteria by which differentiation is recognized in each cell type are provided, and only those effects of 1alpha,25-dihydroxyvitamin D(3) (1,25D) on cell proliferation and survival that are associated with the differentiation process are emphasized. The existing knowledge, often fragmentary, of the signaling pathways that lead to vitamin D-induced differentiation of colon, breast, prostate, squamous cell carcinoma, osteosarcoma, and myeloid leukemia cancer cells is outlined. The important distinctions between the different mechanisms of 1,25D-induced differentiation that are cell-type and cell-context specific are pointed out where known. There is a considerable body of evidence that the principal human cancer cells can be suitable candidates for chemoprevention or differentiation therapy with vitamin D. However, further studies are needed to fully understand the underlying mechanisms in order to improve the therapeutic approaches.
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Affiliation(s)
- Elzbieta Gocek
- Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
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Wang X, Studzinski GP. Raf-1 signaling is required for the later stages of 1,25-dihydroxyvitamin D3-induced differentiation of HL60 cells but is not mediated by the MEK/ERK module. J Cell Physiol 2006; 209:253-60. [PMID: 16883571 PMCID: PMC2814417 DOI: 10.1002/jcp.20731] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
We are interested in determining the signaling pathways for 1,25-dihydroxyvitamin D3 (1,25D)-induced differentiation of HL60 leukemic cells. One possible candidate is Raf-1, which is known to signal cell proliferation and neoplastic transformation through MEK, ERK, and downstream targets. It can also participate in the regulation of cell survival and various forms of cell differentiation, though the precise pathways are less well delineated. Here we report that Raf-1 has a role in monocytic differentiation of human myeloid leukemia HL60, which is not mediated by MEK and ERK, but likely by direct interaction with p90RSK. Specifically, we show that Raf-1 and p90RSK are increasingly activated in the later stages of differentiation of HL60 cells, at the same time as activation of MEK and ERK is decreasing. Transfection of a wild-type Raf-1 construct enhances 1,25D-induced differentiation, while antisense Raf-1 or short interfering (si) Raf-1 reduces 1,25D-induced differentiation. In contrast, antisense oligodeoxynucleotides (ODN) and siRNAs to MEK or ERK have no detectable effect on differentiation. In late stage differentiating cells Raf-1 and p90RSK are found as a complex, and inhibition of Raf-1, but not MEK or ERK expression reduces the levels of phosphorylated p90 RSK. These findings support the thesis that Raf-1 signals cell proliferation and cell differentiation through different intermediary proteins.
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Affiliation(s)
| | - George P. Studzinski
- Correspondence to: George P. Studzinski, Department of Pathology and Laboratory Medicine, 185 South Orange Avenue, Newark, NJ 07103.
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Pawelczyk T, Sakowicz M, Podgorska M, Szczepanska-Konkel M. Insulin induces expression of adenosine kinase gene in rat lymphocytes by signaling through the mitogen-activated protein kinase pathway. Exp Cell Res 2003; 286:152-63. [PMID: 12729803 DOI: 10.1016/s0014-4827(03)00090-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The activity of adenosine kinase (AK) was significantly impaired in splenocytes isolated from diabetic rats. Administration of insulin to diabetic animals restored AK activity, protein, and mRNA levels in diabetic splenocytes. Experiments performed on cultured rat lymphocytes demonstrated that insulin did not change the stability of AK mRNA. Insulin induced AK gene expression in a dose- and time-dependent manner. Maximal increases in AK mRNA (3.9-fold) and activity level (3.7-fold) were observed at the fourth and fifth hours of cell incubation with 10 nM insulin, respectively. The insulin effect on AK expression was not influenced by dibutyryl cAMP (dcAMP). On the other hand dcAMP weakly increased (1.7-fold) basal expression of AK. Exposure of rat lymphocytes to wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3K), or rapamycin, an inhibitor of mTOR, did not affect the ability of insulin to stimulate expression of AK. Prior treatment of the cells with 10 microM PD98059, an inhibitor of mitogen-activated protein kinase (MAPK) kinase (MEK) completely blocked insulin-stimulated expression of AK gene. Insulin produced a significant transient increase in the tyrosine phosphorylation of ERK1/2, and PD98059 inhibited this phosphorylation. Furthermore exposure of cells to insulin has resulted in transient phosphorylation of Elk-1 on Ser-383 and sustained elevation of c-Jun and c-Fos protein. The maximal phosphorylation of Elk-1 was observed at 15 min, and was blocked by PD98059. We concluded that insulin stimulates AK gene expression through a series of events occurring sequentially. This includes activation of the MAPK cascade and subsequent phosphorylation of Elk-1 followed by increased expression of c-fos and c-jun genes.
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Affiliation(s)
- Tadeusz Pawelczyk
- Department of Molecular Medicine, Medical University of Gdansk, ul. Debinki 7, paw. 29, 80-211 Gdansk, Poland.
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Dhillon AS, Meikle S, Peyssonnaux C, Grindlay J, Kaiser C, Steen H, Shaw PE, Mischak H, Eychène A, Kolch W. A Raf-1 mutant that dissociates MEK/extracellular signal-regulated kinase activation from malignant transformation and differentiation but not proliferation. Mol Cell Biol 2003; 23:1983-93. [PMID: 12612072 PMCID: PMC149463 DOI: 10.1128/mcb.23.6.1983-1993.2003] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
It is widely thought that the biological outcomes of Raf-1 activation are solely attributable to the activation of the MEK/extracellular signal-regulated kinase (ERK) pathway. However, an increasing number of reports suggest that some Raf-1 functions are independent of this pathway. In this report we show that mutation of the amino-terminal 14-3-3 binding site of Raf-1 uncouples its ability to activate the MEK/ERK pathway from the induction of cell transformation and differentiation. In NIH 3T3 fibroblasts and COS-1 cells, mutation of serine 259 resulted in Raf-1 proteins which activated the MEK/ERK pathway as efficiently as v-Raf. However, in contrast to v-Raf, RafS259 mutants failed to transform. They induced morphological alterations and slightly accelerated proliferation in NIH 3T3 fibroblasts but were not tumorigenic in mice and behaved like wild-type Raf-1 in transformation assays measuring loss of contact inhibition or anchorage-independent growth. Curiously, the RafS259 mutants inhibited focus induction by an activated MEK allele, suggesting that they can hyperactivate negative-feedback pathways. In primary cultures of postmitotic chicken neuroretina cells, RafS259A was able to sustain proliferation to a level comparable to that sustained by the membrane-targeted transforming Raf-1 protein, RafCAAX. In contrast, RafS259A was only a poor inducer of neurite formation in PC12 cells in comparison to RafCAAX. Thus, RafS259 mutants genetically separate MEK/ERK activation from the ability of Raf-1 to induce transformation and differentiation. The results further suggest that RafS259 mutants inhibit signaling pathways required to promote these biological processes.
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Affiliation(s)
- Amardeep S Dhillon
- The Beatson Institute for Cancer Research, CR-UK Beatson Laboratories, Garscube Estate, Bearsden, Glasgow G61 1BD, Scotland, UK.
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Mondal D, Larussa VF, Agrawal KC. Synergistic antiadipogenic effects of HIV type 1 protease inhibitors with tumor necrosis factor alpha: suppression of extracellular insulin action mediated by extracellular matrix-degrading proteases. AIDS Res Hum Retroviruses 2001; 17:1569-84. [PMID: 11779345 DOI: 10.1089/088922201753341988] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Long-term use of HIV-1 protease inhibitors (PIs) is associated with a lipodystrophy syndrome. To delineate the associated mechanisms, adipogenesis was determined in 3T3-L1 cells in the presence or absence of either indinavir (2-50 microg/ml) or ritonavir (0.4-10 microg/ml). A concentration-dependent decrease in both lipid (4-59%) and triglyceride (11-49%) levels was seen after 10 days of exposure. Simultaneous treatment with TNF-alpha showed a synergistic suppression in lipid levels by 45-95% at 10 U/ml and almost complete suppression at 100 U/ml. The effect of PIs on insulin-induced lipogenesis was monitored by [(14)C)]glucose incorporation into lipids, which was suppressed by 21-86% in a concentration-dependent manner. Insulin-sensitizing agent, troglitazone (80 and 400 nM), effectively blocked the PI-mediated adipogenic suppression. Preadipocyte factor 1 gene (pref-1) expression, as monitored by RT-PCR, was downregulated (4- to 6-fold) within 48 hr after insulin stimulation; however, a smaller decrease (1.2- to 1.8-fold) was observed in PI-exposed cells. The decrease in proteolytic activity of matrix metalloproteases (MMP-2 and MMP-9) during adipogenesis was reversed on exposure to the PIs. Similarly, the plasminolytic activity was increased and plasminogen activator inhibitor (PAI) activity was decreased in supernatants from PI-treated cells. The insulin-mediated induction (3- to 4-fold) of PAI-1 and PAI-2 message was suppressed on exposure to PIs, which was reversed by troglitazone treatment. Thus, the HIV-1 PIs may suppress adipogenesis by disrupting the concerted actions of host proteases that regulate ECM integrity required for initiation of differentiation.
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Affiliation(s)
- D Mondal
- Department of Pharmacology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
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10
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Hall DJ, Cui J, Bates ME, Stout BA, Koenderman L, Coffer PJ, Bertics PJ. Transduction of a dominant-negative H-Ras into human eosinophils attenuates extracellular signal-regulated kinase activation and interleukin-5-mediated cell viability. Blood 2001; 98:2014-21. [PMID: 11567984 DOI: 10.1182/blood.v98.7.2014] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Inhibition of eosinophil apoptosis by exposure to interleukin-5 (IL-5) is associated with the development of tissue eosinophilia and may contribute to the inflammation characteristic of asthma. Analysis of the signaling events associated with this process has been hampered by the inability to efficiently manipulate eosinophils by the introduction of active or inhibitory effector molecules. Evidence is provided, using a dominant-negative N17 H-Ras protein (dn-H-Ras) and MEK inhibitor U0126, that activation of the Ras-Raf-MEK-ERK pathway plays a determining role in the prolongation of eosinophil survival by IL-5. For these studies, a small region of the human immunodeficiency virus Tat protein, a protein transduction domain known to enter mammalian cells efficiently, was fused to the N-terminus of dn-H-Ras. The Tat-dn-H-Ras protein generated from this construct transduced isolated human blood eosinophils at more than 95% efficiency. When Tat-dn-H-Ras-transduced eosinophils were treated with IL-5, they exhibited a time- and dosage-dependent reduction in extracellular regulated kinase 1 and 2 activation and an inhibition of p90 Rsk1 phosphorylation and IL-5-mediated eosinophil survival in vitro. In contrast, Tat-dn-H-Ras did not inhibit CD11b up-regulation or STAT5 tyrosine phosphorylation. These data demonstrate that Tat dominant-negative protein transduction can serve as an important and novel tool in studying primary myeloid cell signal transduction in primary leukocytes and can implicate the Ras-Raf-MEK-ERK pathway in IL-5-initiated eosinophil survival.
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Affiliation(s)
- D J Hall
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI 53706, USA
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11
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Kim SW, Muise AM, Lyons PJ, Ro HS. Regulation of adipogenesis by a transcriptional repressor that modulates MAPK activation. J Biol Chem 2001; 276:10199-206. [PMID: 11152475 DOI: 10.1074/jbc.m010640200] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitogen-activated protein kinase (MAPK) is required for cell growth and cell differentiation. In adipogenesis, MAPK activation opposes the differentiation process. The regulatory mechanisms or the cellular factors that regulate the switch between growth and differentiation in the adipogenic lineage have been largely unelucidated. We show here that AEBP1, a transcriptional repressor that is down-regulated during adipogenesis, complexes and protects MAPK from its specific phosphatase in mammalian cells. We further show evidence that the modulation of MAPK activation by AEBP1 is a biologically relevant process in adipogenesis. Our results suggest that modulation of MAPK activation by the protective effect of AEBP1 may constitute a critical part in the determination between cell growth and differentiation in the adipogenic lineage. The proposed mode of action by which a transcription factor regulates MAPK activation is novel.
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Affiliation(s)
- S W Kim
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Sir Charles Tupper Medical Bldg., Dalhousie University, Halifax, Nova Scotia B3H 4H7, Canada
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12
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Janosch P, Kieser A, Eulitz M, Lovric J, Sauer G, Reichert M, Gounari F, Büscher D, Baccarini M, Mischak H, Kolch W. The Raf-1 kinase associates with vimentin kinases and regulates the structure of vimentin filaments. FASEB J 2000; 14:2008-21. [PMID: 11023985 DOI: 10.1096/fj.99-0883com] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Using immobilized GST-Raf-1 as bait, we have isolated the intermediate filament protein vimentin as a Raf-1-associated protein. Vimentin coimmunoprecipitated and colocalized with Raf-1 in fibroblasts. Vimentin was not a Raf-1 substrate, but was phosphorylated by Raf-1-associated vimentin kinases. We provide evidence for at least two Raf-1-associated vimentin kinases and identified one as casein kinase 2. They are regulated by Raf-1, since the activation status of Raf-1 correlated with the phosphorylation of vimentin. Vimentin phosphorylation by Raf-1 preparations interfered with its polymerization in vitro. A subset of tryptic vimentin phosphopeptides induced by Raf-1 in vitro matched the vimentin phosphopeptides isolated from v-raf-transfected cells labeled with orthophosphoric acid, indicating that Raf-1 also induces vimentin phosphorylation in intact cells. In NIH 3T3 fibroblasts, the selective activation of an estrogen-regulated Raf-1 mutant induced a rearrangement and depolymerization of the reticular vimentin scaffold similar to the changes elicited by serum treatment. The rearrangement of the vimentin network occurred independently of the MEK/ERK pathway. These data identify a new branch point in Raf-1 signaling, which links Raf-1 to changes in the cytoskeletal architecture.
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Affiliation(s)
- P Janosch
- The Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, U.K.
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Boney CM, Gruppuso PA, Faris RA, Frackelton AR. The critical role of Shc in insulin-like growth factor-I-mediated mitogenesis and differentiation in 3T3-L1 preadipocytes. Mol Endocrinol 2000; 14:805-13. [PMID: 10847583 DOI: 10.1210/mend.14.6.0487] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Insulin-like growth factor-I (IGF-I) stimulates mitogenesis in proliferating preadipocytes, but when cells reach confluence and become growth arrested, IGF-I stimulates differentiation into adipocytes. IGF-I induces signaling pathways that involve IGF-I receptor-mediated tyrosine phosphorylation of Shc and insulin receptor substrate 1 (IRS-1). Either of these adaptor proteins can lead to activation of the three-kinase cascade ending in activation of the extracellular signal-regulated kinase 1 and -2 (ERK-1 and -2) mitogen-activated protein kinases (MAPKs). Several lines of evidence suggest that activation of MAPK inhibits 3T3-L1 preadipocyte differentiation. We have shown that IGF-I stimulation of MAPK activity is lost as 3T3-L1 preadipocytes begin to differentiate. This change in MAPK signaling coincides with loss of IGF-I-mediated Shc, but not IRS-1, tyrosine phosphorylation. We hypothesized that down-regulation of MAPK via loss of proximal signaling through Shc is an early component in the IGF-I switch from mitogenesis to differentiation in 3T3-L1 preadipocytes. Treatment of subconfluent cells with the MEK inhibitor PD098059 inhibited both IGF-I-activation of MAPK as well as 3H-thymidine incorporation. PD098059, in the presence of differentiation-inducing media, accelerated differentiation in subconfluent cells as measured by expression of adipocyte protein-2 (aP-2), peroxisome proliferator-activated receptor gamma (PPARgamma) and lipoprotein lipase (LPL). Transient transfection of subconfluent cells with Shc-Y317F, a dominant-negative mutant, attenuated IGF-I-mediated MAPK activation, inhibited DNA synthesis, and accelerated expression of differentiation markers aP-2, PPARgamma, and LPL. We conclude that signaling through Shc to MAPK plays a critical role in mediating IGF-I-stimulated 3T3-L1 mitogenesis. Our results suggest that loss of the ability of IGF-I to activate Shc signaling to MAPK may be an early component of adipogenesis in 3T3-L1 cells.
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Affiliation(s)
- C M Boney
- Department of Pediatrics Rhode Island Hospital, Providence 02903, USA.
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Schipper HM, Agarwal-Mawal A, Paudel HK. The topography and subcellular distribution of mitogen-activated protein kinase kinase1 (MEK1) in adult rat brain and differentiating PC12 cells. Neuroscience 1999; 93:585-95. [PMID: 10465442 DOI: 10.1016/s0306-4522(99)00120-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Mitogen-activated protein kinase signal transduction pathway involved in the regulation of proliferation and differentiation of various mammalian cells consists of a sequential activation of three protein kinases, Raf, mitogen-activated protein kinase kinase, and mitogen-activated protein kinase. These kinases are highly expressed in brain and play an important role in neuronal signalling. In this study, to further characterize mitogen-activated protein kinase signalling pathway in brain, we have elucidated the topography and subcellular distribution of mitogen-activated protein kinase kinasel in adult rat brain and differentiating PC12 cells. Our immunohistochemical data indicate that mitogen-activated protein kinase kinase1 is widely distributed throughout the brain and expressed prominently in cortex, hippocampus, brainstem, hypothalamus and cerebellum. In these areas of brain mitogen-activated protein kinase kinasel is exclusively neuronal in origin and is localized within perikarya and dendrites. Confocal microscopy data has determined that a portion of mitogen-activated protein kinase kinase1 in rat brain is co-localized with microtubules. This co-localization was observed only within neuritic shaft and cilia of ventricular ependymal cells. In nerve growth factor-induced differentiating PC12 cells, mitogen-activated protein kinase kinase1 displays co-localization with microtubules within proximal regions of neuritic shafts and their junctions with the cell somas. From bovine brain extract, mitogen-activated protein kinase kinasel co-purifies with microtubules. In vitro kinase assay detected mitogen-activated protein kinase kinase1 activity within purified microtubules. These observations indicate that mitogen-activated protein kinase kinase1 is associated with microtubules within some specialized compartments of the brain and microtubule-associated mitogen-activated protein kinase kinase1 is catalytically active.
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Affiliation(s)
- H M Schipper
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, and Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada
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Høvik KE, Wu P, Gordeladze JO. The inhibitory guanine nucleotide-binding protein Gi2alpha induces and potentiates adipocyte differentiation. Lipids 1999; 34:355-62. [PMID: 10443968 DOI: 10.1007/s11745-999-0373-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The present study further elucidates the involvement of the alpha-subunit of the GTP-binding protein Gi2 in the differentiation of murine 3T3-L1 cells. Control and vector-transfected cells attained a fully differentiated adipocyte phenotype showing ample lipid droplets. Cells expressing wild type (WT)-Gi2alpha or the constitutively active R179E-Gi2alpha, however, became enlarged, less confluent, and produced large amounts of lipids. Differentiation consistently increased the triglyceride (TAG) content in control cells. In both WT-Gi2alpha and R179E-Gi2alpha clones, a marked increase in TAG could be detected even prior to insulin/dexamethasone/isobutyl methylxanthine exposure. The activity of palmitoyl-CoA synthetase (PCS) and glycerophosphate acyltransferase (GPAT) also increased upon differentiation. WT-Gi2alpha and R179E-Gi2alpha overexpression also enhanced PCS and GPAT activities even before differentiation medium was added. The total amount of phospholipids (PL) generally increased upon differentiation; however, pre- and postdifferentiation values were insignificantly different in cells expressing WT-Gi2alpha and R179E-Gi2alpha. Differentiation altered the PL profile with a relative shift from phosphatidylcholine and phosphatidylethanolamine to phosphatidylinositol (PI) in differentiated cells. Finally, differentiation yielded a general increase in the activity of basal PI-phospholipase-C activity. Again, cells expressing WT-Gi2alpha and R179E-Gi2alpha demonstrated elevated enzyme activity and enhanced second messenger accumulation subsequent to differentiation. In summary, cells with the R179E-mutants of Gi2alpha exhibited stimulated lipid turnover and accumulation in both undifferentiated and differentiated cells.
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Affiliation(s)
- K E Høvik
- Institute of Medical Biochemistry, University of Oslo, Norway.
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16
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King FJ, Hu E, Harris DF, Sarraf P, Spiegelman BM, Roberts TM. DEF-1, a novel Src SH3 binding protein that promotes adipogenesis in fibroblastic cell lines. Mol Cell Biol 1999; 19:2330-7. [PMID: 10022919 PMCID: PMC84025 DOI: 10.1128/mcb.19.3.2330] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Src homology 3 (SH3) motif is found in numerous signal transduction proteins involved in cellular growth and differentiation. We have purified and cloned a novel protein, DEF-1 (differentiation-enhancing factor), from bovine brain by using a Src SH3 affinity column. Ectopic expression of DEF-1 in fibroblasts resulted in the differentiation of a significant fraction of the culture into adipocytes. This phenotype appears to be related to the induction of the transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma), since DEF-1 NIH 3T3 cells demonstrated augmented levels of PPARgamma mRNA and, when treated with activating PPARgamma ligands, efficient induction of differentiation. Further evidence for a role for DEF-1 in adipogenesis was provided by heightened expression of DEF-1 mRNA in adipose tissue isolated from obese and diabetes mice compared to that in tissue isolated from wild-type mice. However, DEF-1 mRNA was detected in multiple tissues, suggesting that the signal transduction pathway(s) in which DEF-1 is involved is not limited to adipogenesis. These results suggest that DEF-1 is an important component of a signal transduction process that is involved in the differentiation of fibroblasts and possibly of other types of cells.
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Affiliation(s)
- F J King
- Department of Cancer Biology, The Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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17
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Ventura JJ, Roncero C, Fabregat I, Benito M. Glucocorticoid receptor down-regulates c-Jun amino terminal kinases induced by tumor necrosis factor alpha in fetal rat hepatocyte primary cultures. Hepatology 1999; 29:849-57. [PMID: 10051489 DOI: 10.1002/hep.510290339] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The effect of dexamethasone on Jun N-terminal kinase (JNK) activity was assayed by using fetal hepatocytes in primary culture. The addition of tumor necrosis factor alpha (TNF-alpha) caused an increase in JNK in a dose- and time-dependent manner. We show that activation of JNK by this extracellular signal is inhibited by dexamethasone in a dose-dependent fashion. This inhibitory effect was observed in cells treated for 10 minutes with dexamethasone in the presence of protein phosphatase inhibitors such as orthovanadate or okadaic acid, or in cells previously treated with actinomycin D. Glucocorticoid receptor (GR) can be precipitated with the fusion protein, GST-c-Jun (1-79), bound to agarose beads. However, the inhibitory effect of glucocorticoids on JNK activity was also observed using ATF-2 as substrate. In addition, dexamethasone inhibits JNK phosphorylation induced by TNF-alpha. Finally, we show that GR can also be phosphorylated in tyrosine residues in response to TNF-alpha and epidermal growth factor (EGF) upon ligand-binding. Our results suggest that the anti-inflammatory effect of glucocorticoids on the inflammatory pathways induced by TNF-alpha can be explained, at least in part, by modulating JNK activity through a direct protein-protein interaction; the JNK phosphorylation and tyrosine-phosphorylation state of GR may be regulatory steps also involved in that effect.
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Affiliation(s)
- J J Ventura
- Departamento de Bioquímica y Biología Molecular, Centro Mixto C.S. I.C./U.C.M., Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, Spain
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18
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Sorisky A. From preadipocyte to adipocyte: differentiation-directed signals of insulin from the cell surface to the nucleus. Crit Rev Clin Lab Sci 1999; 36:1-34. [PMID: 10094092 DOI: 10.1080/10408369991239169] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
An alarming rise in obesity, and the accompanying threat of type 2 diabetes mellitus and cardiovascular disease, have attracted worldwide attention. The pathogenic mechanism(s) underlying obesity remains obscure. However, new cellular and molecular insights about the development of adipose tissue, with respect to adipocyte number (hyperplasia) and size (hypertrophy), are occurring at a rapid pace. Specialized fibroblasts (preadipocytes) committed to the adipocyte lineage are present throughout life. Primary cell culture systems and immortalized cell line models of preadipocytes have advanced the study of adipocyte differentiation (adipogenesis). Differentiation-inducing cues are able to trigger a complex network of intracellular signaling pathways in the preadipocyte, allowing signals from cell-surface receptors to reach nuclear transcription factors that regulate the genetic program of adipocyte differentiation. The extracellular matrix environment of the preadipocyte, known to modulate adipogenesis, may act by altering some of these signaling events.
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Affiliation(s)
- A Sorisky
- Department of Medicine and Biochemistry, Loeb Research Institute, Ottawa Civic Hospital, University of Ottawa, Ontario, Canada
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19
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Uehara T, Tokumitsu Y, Nomura Y. Pertussis toxin-sensitive and insensitive intracellular signalling pathways in undifferentiated 3T3-L1 cells stimulated by insulin converge with phosphatidylinositol 3-kinase upstream of the Ras mitogen-activated protein kinase cascade. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 259:801-8. [PMID: 10092867 DOI: 10.1046/j.1432-1327.1999.00100.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have previously reported that pertussis toxin (PTX)-sensitive GTP binding protein (G-protein) and phosphatidylinositol 3-kinase (PI 3-K) are involved in adipocyte differentiation of 3T3-L1 cells induced by insulin/dexamethasone/methylisobutyl xanthine. The aim of this study was to examine the effect of PTX on the tyrosine kinase cascade stimulated by insulin acting through insulin-like growth factor-I (IGF-I) receptors in undifferentiated 3T3-L1 cells. A high level of mitogen-activated protein kinase (MAPK) activation was sustained for up to 4 h after insulin treatment, and mobility shifted and tyrosine phosphorylated MAPK was also detected. MAPK kinase activity measured by the incorporation of 32P into kinase-negative recombinant MAPK was enhanced by insulin treatment. We previously discovered that insulin activates Ras and that this is mediated by wortmannin-sensitive PI 3-K. Tyrosine-phosphorylation of IRS-1 and Shc also occurred in response to insulin. Subsequently, we investigated the effects of PTX on the activation of these proteins by insulin. Interestingly, treating 3T3-L1 cells with PTX attenuates the activation by insulin of both the Ras-MAPK cascade and PI 3-K. In contrast, neither tyrosine-phosphorylation of IRS-1 and Shc nor the interaction between IRS-1 and PI 3-K is sensitive to PTX. However, activation of the Ras-MAPK cascade and tyrosine-phosphorylation of Shc by epidermal growth factor are insensitive to PTX. These results indicate that there is another pathway which regulates PI 3-K and Ras-MAPK, independent of the pathway mediated by IGF-I receptor kinase. These findings suggest that in 3T3-L1 fibroblasts, PTX-sensitive G-proteins cross-talk with the Ras-MAPK pathway via PI 3-K by insulin acting via IGF-I receptors.
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Affiliation(s)
- T Uehara
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Japan
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20
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Clark R, Stewart M, Miskimins WK, Miskimins R. Involvement of MAP kinase in the cyclic AMP induction of myelin basic protein gene expression. Int J Dev Neurosci 1998; 16:323-31. [PMID: 9829168 DOI: 10.1016/s0736-5748(98)00045-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cyclic AMP is involved in the differentiation of oligodendrocyte and Schwann cell progenitors into mature myelin producing cells. The involvement of MAP kinases in this pathway was investigated in the D6P2T cell line. This cell line can be induced to display a differentiated phenotype characterized by myelin basic protein gene expression by increased cyclic AMP. Blocking MAP kinase activity with inhibitors of the activating kinase, MEK, by expression of a dominant negative MAP kinase or by expression of the MAP kinase inactivating phosphatase Mkp-1 all blocked the activation of the myelin basic protein promoter in D6P2T cells. In addition, blocking MAP kinase activation during differentiation of an oligodendrocyte-like cell line, CG4, also leads to inhibition of MBP expression. These findings suggest a role for MAP kinase in the cyclic AMP stimulated expression of the myelin basic protein gene during differentiation.
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Affiliation(s)
- R Clark
- Department of Biochemistry and Molecular Biology, University of South Dakota School of Medicine, Vermillion 57069, USA
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21
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Affiliation(s)
- T S Lewis
- Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Colorado, Boulder 80309, USA
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22
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Pelech SL, Charest DL. MAP kinase-dependent pathways in cell cycle control. PROGRESS IN CELL CYCLE RESEARCH 1998; 1:33-52. [PMID: 9552352 DOI: 10.1007/978-1-4615-1809-9_4] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Mitogen-activated protein kinases such as Erk1 and Erk2 serve as a paradigm for a growing family of proline-directed protein kinases that mediate entry, progression and exit from the cell cycle in diverse eukaryotic cells. These enzymes function within highly conserved modules of sequentially activating protein kinases that transduce signals from diverse extracellular stimuli. In vertebrates, at least three distinct kinases modules have been characterized. Mitogens induce the sequential activation of the kinases Raf1-->Mek1-->Erk2-->Rsk via the G-protein Ras. Stress factors stimulate c-Jun activation through a related kinase pathway involving Mekk-->Sek-->SAPK c-Jun, and hsp27 phosphorylation via the MKK3-->Hog-->MAPKAPK-2 hsp27 route. Genetic and biochemical studies, for example from budding yeast, imply the existence of several related protein kinase modules that can operate in parallel or within integrated systems.
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Affiliation(s)
- S L Pelech
- Biomedical Research Centre, University of British Columbia, Vancouver, Canada
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23
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Crespo P, Font de Mora J, Aaronson DS, Santos E, Gutkind JS. Transforming G protein-coupled receptors block insulin and ras-induced adipocytic differentiation in 3T3-L1 cells: evidence for a PKC and MAP kinase independent pathway. Biochem Biophys Res Commun 1998; 245:554-61. [PMID: 9571194 DOI: 10.1006/bbrc.1998.8480] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have used the expression of muscarinic m1 receptors in the preadipocytic 3T3-L1 cell line for dissecting the nature of the G protein-linked pathways governing adipocytic differentiation, a complex process controlled by many stimuli and their downstream targets. 3T3-L1 cells can be differentiated by insulin or by ras oncogenes, and MAP kinase has been implicated in this process. However, m1 stimulation failed to induce differentiation of 3T3-L1 cells. Furthermore, it prevented insulin or v-ras-induced adipocytic differentiation, utilizing a protein kinase C-independent pathway. m1 stimulation did not alter the phosphorylation state of the insulin receptor substrates IRS-1 and SHC, nor the recruitment of Grb-2. Interestingly, whereas m1 receptors potently activated MAP kinase, another differentiation-inhibitor, TNF alpha, did not affect it. These results suggest that the control of adipocytic differentiation can occur utilizing a biochemical route independent of protein kinase C, and acting downstream, or independently from the Ras-MAP kinase pathway.
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Affiliation(s)
- P Crespo
- Molecular Signaling Unit, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892, USA.
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24
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Boney CM, Smith RM, Gruppuso PA. Modulation of insulin-like growth factor I mitogenic signaling in 3T3-L1 preadipocyte differentiation. Endocrinology 1998; 139:1638-44. [PMID: 9528944 DOI: 10.1210/endo.139.4.5920] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Insulin-like growth factor I (IGF-I) stimulates mitogenesis in proliferating 3T3-L1 preadipocytes. However, IGF-I functions to stimulate differentiation once growth arrest occurs at confluence. Epidermal growth factor (EGF) is also a potent mitogen in these cells, but inhibits differentiation of preadipocytes. We compared mitogenic signaling via the mitogen-activated protein kinase (MAPK) pathway in response to IGF-I or EGF in proliferating, growth-arrested, and differentiating 3T3-L1 cells. IGF-I stimulation of MAPK was rapid and maximal in proliferating 3T3-L1 preadipocytes, but decreased greatly in differentiating cells. EGF was more potent than IGF-I in stimulating MAPK activity in 3T3-L1 cells, and activation of MAPK was maintained in differentiating cells. These results suggest an uncoupling of MAPK activation specific to IGF-I-mediated 3T3-L1 preadipocyte differentiation. Studies of proximal signaling revealed Shc phosphorylation and Shc/Grb2 complex formation in IGF-I-treated proliferating, but not differentiating, cells. Insulin receptor substrate-1 phosphorylation after IGF-I treatment was present in proliferating, quiescent, and differentiating preadipocytes. Shc phosphorylation and Grb2 association after EGF treatment were present throughout all phases of growth. The change in IGF-I signaling via Shc phosphorylation and MAPK activity during 3T3-L1 differentiation indicates that loss of IGF-I mitogenic signaling via the MAPK pathway is part of the differentiation process.
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Affiliation(s)
- C M Boney
- Department of Pediatrics, Rhode Island Hospital and Brown University, Providence 02903, USA.
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25
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Joneson T, Fulton JA, Volle DJ, Chaika OV, Bar-Sagi D, Lewis RE. Kinase suppressor of Ras inhibits the activation of extracellular ligand-regulated (ERK) mitogen-activated protein (MAP) kinase by growth factors, activated Ras, and Ras effectors. J Biol Chem 1998; 273:7743-8. [PMID: 9516483 DOI: 10.1074/jbc.273.13.7743] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Kinase suppressor of Ras (KSR) is a loss-of-function allele that suppresses the rough eye phenotype of activated Ras in Drosophila and the multivulval phenotype of activated Ras in Caenorhabditis elegans. Genetic and biochemical studies suggest that KSR is a positive regulator of Ras signaling that functions between Ras and Raf or in a pathway parallel to Raf. We examined the effect of mammalian KSR expression on the activation of extracellular ligand-regulated (ERK) mitogen-activated protein (MAP) kinase in fibroblasts. Ectopic expression of KSR inhibited the activation of ERK MAP kinase by insulin, phorbol ester, or activated alleles of Ras, Raf, and mitogen and extracellular-regulated kinase. Expression of deletion mutants of KSR demonstrated that the KSR kinase domain was necessary and sufficient for the inhibitory effect of KSR on ERK MAP kinase activity. KSR inhibited cell transformation by activated RasVal-12 but had no effect on the ability of RasVal-12 to induce membrane ruffling. These data indicate that KSR is a potent modulator of a signaling pathway essential to normal and oncogenic cell growth and development.
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Affiliation(s)
- T Joneson
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA
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26
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Roncero C, Ventura JJ, Sánchez A, Bois-Joyeux B, Mesa ML, Thomassin H, Danan JL, Benito M, Fabregat I. Phorbol esters down-regulate alpha-fetoprotein gene expression without affecting growth in fetal hepatocytes in primary culture. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1402:151-64. [PMID: 9561801 DOI: 10.1016/s0167-4889(98)00005-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The effects of phorbol esters (phorbol-12,13-dibutyrate, PDB) on alpha-fetoprotein expression and cell growth were assayed by using fetal hepatocytes in primary culture. PDB acts synergistically with epidermal growth factor (EGF) to specifically decrease alpha-fetoprotein (AFP) mRNA levels, without affecting the expression of other genes of the same family, such as albumin and Vitamin D-binding protein (DBP). This effect is PDB-dose dependent, maximal effects being at 10 ng/ml. The implication of protein kinase C (PKC) in this effect seems clear since bisindolylmaleimide (BIS), a specific PKC inhibitor, completely blocks the PDB effect on AFP expression. Nuclear run-on experiments show that the decrease in AFP mRNA levels is mainly due to an inhibition in the transcription rate of the gene. Determination of PKC activities shows that fetal hepatocytes contain mainly Ca(2+)-independent isoenzymes, which patterns of activation was not modified by EGF plus PDB treatment with respect to PDB treatment. We have found that MAPK and JNK activities, c-jun and c-fos mRNA levels and AP-1 binding activity are notably increased when cells are incubated with both EGF and PDB, PDB does not stimulate growth of fetal hepatocytes, measured either as [3H]-thymidine incorporation into DNA or by cell cycle analysis using flow cytometry. All these results suggest that activation of PKC may affect liver gene expression rather than cell growth in fetal hepatocytes.
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Affiliation(s)
- C Roncero
- Departamento de Bioquímica y Biología Molecular, Centro Mixto C.S.I.C./U.C.M. Facultad de Farmacia, Universidad Complutense de Madrid, Spain.
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27
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Gagnon A, Sorisky A. The effect of glucose concentration on insulin-induced 3T3-L1 adipose cell differentiation. OBESITY RESEARCH 1998; 6:157-63. [PMID: 9545023 DOI: 10.1002/j.1550-8528.1998.tb00330.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We examined the effect of glucose concentration on insulin-induced 3T3-L1 adipose cell differentiation. Oil Red O staining of neutral lipid, cellular triglyceride mass, and glycerol phosphate dehydrogenase (GPDH) activity, were greater in 3T3-L1 cells cultured at 5 mM vs. 25 mM glucose. GPDH activity was 2- to 4-fold higher at 5 mM vs. 25 mM glucose over a range of insulin concentrations (0.1 to 100 nM). Insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) was 1.7-fold greater, and insulin-stimulated phosphoinositide 3-kinase association with IRS-1 was 2.3-fold higher, at 5 mM vs. 25 mM glucose. These effects of glucose were not caused by alterations in IRS-1 mass or cell-surface insulin binding. In preadipose cells at 5 mM glucose, expression of the leukocyte antigen-related (LAR) protein tyrosine phosphatase (negative regulator of insulin signaling) was 63% of the level at 25 mM glucose. Our data demonstrate that glucose concentration affects insulin-induced 3T3-L1 adipose cell differentiation as well as differentiation-directed insulin signaling pathways. Alterations in LAR expression potentially may be involved in modulating these responses.
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Affiliation(s)
- A Gagnon
- Ottawa Civic Hospital Loeb Research Institute, Department of Medicine, University of Ottawa, Ontario, Canada
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28
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Indolfi C, Avvedimento EV, Rapacciuolo A, Esposito G, Di Lorenzo E, Leccia A, Pisani A, Chieffo A, Coppola A, Chiariello M. In vivo gene transfer: prevention of neointima formation by inhibition of mitogen-activated protein kinase kinase. Basic Res Cardiol 1997; 92:378-84. [PMID: 9464861 DOI: 10.1007/bf00796211] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND The mitogen-activated protein kinase kinase (MAPKK) is a protein downstream ras which is rapidly activated in cells stimulated with various extracellular signals. These proteins are believed to play a pivotal role in integrating and transmitting transmembrane signals required for cell growth. METHODS AND RESULTS To study the effect of inhibition of MAPKK on smooth muscle cell (SMC) proliferation in vivo after vascular injury, we performed experimental balloon angioplasty using the standard Clowes technique in male Wistar rats 14-weeks old. The animals did not receive any treatment after vascular injury (N = 6) or were randomly assigned to receive, after balloon injury, a 30% (w/v) pluronic gel solution applied to the injured carotid artery, containing respectively: 1) no plasmid DNA (n = 10); 2) RSV-lacZ (encoding the beta-galactosidase gene) as control gene without effects on SMC proliferation (n = 10); 3) Tg-CAT (encoding cloramphenicol acetyl-transferase gene under the control of thyreoglobulin promoter) as an additional control gene without effects on SMC proliferation (n = 7): 4) a negative mutant of Mitogen-Activated Protein Kinase Kinase (MAPKK-) (n = 13). Fourteen days after vascular injury, carotid arteries were removed and cross sections were cut and stained with hematoxylin/eosin. Morphometric analysis demonstrated, in the MAPKK- treated rats, a significant reduction of both neointima (0.096+/-.018 mm2 vs. 0.184+/-0.019 mm2, p < 0.01) and neointima/media ratio (0.603+/-0.103 vs. 1.471+/-0.161, p < 0.01) compared to control DNA. CONCLUSIONS The inhibition of MAPKK, by a dominant inhibitor mutant gene, prevents the SMC proliferation after vascular injury in vivo.
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Affiliation(s)
- C Indolfi
- Division of Cardiology, Federico II University, Napoli, Italy.
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29
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Garcés C, Ruiz-Hidalgo MJ, Font de Mora J, Park C, Miele L, Goldstein J, Bonvini E, Porrás A, Laborda J. Notch-1 controls the expression of fatty acid-activated transcription factors and is required for adipogenesis. J Biol Chem 1997; 272:29729-34. [PMID: 9368042 DOI: 10.1074/jbc.272.47.29729] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Notch, a transmembrane receptor member of the homeotic epidermal growth factor-like family of proteins, participates in cell-to-cell signaling to control cell fate during development. Activated Notch-1 constructs lacking the extracellular region prevent differentiation of several mammalian cells in vitro. This effect, however, bypasses the normal mechanisms of cell-to-cell interactions in which Notch-1 participates. We investigated the role of Notch-1 in the hormone-induced adipocyte differentiation of 3T3-L1 fibroblasts, a paradigmatic model of adipogenesis that requires cell-to-cell contact. Unlike other differentiation models, Notch-1 expression and function were necessary conditions for adipogenesis. Impaired Notch-1 expression by antisense Notch-1 constructs prevented adipocyte differentiation. Strategies aimed at blocking putative Notch/ligand interactions also blocked adipogenesis, implicating Notch as a critical molecule in cell-to-cell signaling necessary for differentiation. Inhibition of Notch-1 expression or function decreased the expression of peroxisomal proliferator-activated receptors delta and gamma, transcription factors that control adipocyte differentiation and that are up-regulated at cell confluence. These results implicate Notch in the commitment of 3T3-L1 cells to undergo adipogenesis by controlling the expression of the principal regulators of this process.
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Affiliation(s)
- C Garcés
- Laboratory of Immunobiology, Division of Monoclonal Antibodies, Center for Biologics Evaluation and Research, Bethesda, Maryland 20852, USA
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30
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Li D, Lin HH, McMahon M, Ma H, Ann DK. Oncogenic raf-1 induces the expression of non-histone chromosomal architectural protein HMGI-C via a p44/p42 mitogen-activated protein kinase-dependent pathway in salivary epithelial cells. J Biol Chem 1997; 272:25062-70. [PMID: 9312114 DOI: 10.1074/jbc.272.40.25062] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The enzyme activity of mitogen-activated protein kinase (MAP kinase) increases in response to agents acting on a variety of cell surface receptors, including receptors linked to heterotrimeric G proteins. In this report, we demonstrated that Raf-1 protein kinase activity in the mouse parotid glands was induced by chronic isoproterenol administration in whole animals. To investigate the molecular nature underlying cellular responses to Raf-1 activation, we have stably transfected rat salivary epithelial Pa-4 cells with human Raf-1-estrogen receptor fusion gene (DeltaRaf-1:ER) and used mRNA differential display in search of messages induced by DeltaRaf-1:ER activation. Through this approach, the gene encoding non-histone chromosomal protein HMGI-C was identified as one of the target genes activated by oncogenic Raf-1 kinase. Activation of Raf-1 kinase resulted in a delayed and sustained increase of HMGI-C expression in the Pa-4 cells. The induction of HMGI-C mRNA level is sensitive to both the protein synthesis inhibitor cycloheximide and transcription inhibitor actinomycin D. The role of the extracellular signal-related kinase (ERK) signaling pathway in the HMGI-C induction was highlighted by the result that the MAP kinase kinase (MEK) inhibitor, PD 98059, blocked DeltaRaf-1:ER- and 12-O-tetradecanoylphorbol-13-acetate-stimulated HMGI-C induction. Altogether, these findings support the notion that the Raf/MEK/ERK signaling module, at least in part, regulates transcriptional activation of the chromosomal architectural protein HMGI-C.
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Affiliation(s)
- D Li
- Department of Molecular Pharmacology and Toxicology, University of Southern California, Los Angeles, California 90033, USA
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31
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Abstract
The metabolic effects of insulin are initiated by the binding of insulin to the extracellular domain of the insulin receptor within the plasma membrane of muscle and adipose and liver cells. The subsequent activation of the intracellular tyrosine protein kinase activity of the receptor leads to autophosphorylation of the receptor as well as phosphorylation of a number of intracellular proteins. This gives rise to the activation of Ras and phosphatidylinositol 3-kinase and hence to the activation of a number of serine/threanine protein kinases. Many of these kinases appear to be arranged in cascades, including a cascade that results in the activation of mitogen-activated protein kinase and another that may result in the activation of protein kinase B, leading to the inhibition of glycogen synthase kinase-3 and the activation of the 70 kiloDalton ribosomal S6 protein kinase (p70 S6 kinase). We have explored the role of these early events in the the stimulation of glycogen, fatty acid, and protein synthesis by insulin in rat epididymal fat cells. Comparisons have been made between the metabolic effects of insulin and those of epidermal growth factor, since these 2 agents have contrasting effects on p70 S6 kinase and mitogen-activated protein kinase. The effects of wortmannin (which inhibits phosphatidylinositol 3-kinase), and rapamycin (which blocks the activation of p70 S6 kinase) have also been studied. These and other studies indicate that the mitogen-activated protein kinase cascade is probably not important in the acute metabolic effects of insulin, but may have a role in the regulation of gene transcription and hence the more long-term effects of insulin. The short-term metabolic effects of insulin appear to involve at least 3 distinct signaling pathways: (1) those leading to increases in glucose transport and the activation of glycogen synthase, acetyl-CoA carboxylase, eukaryotic initiation factor-2B, and phosphodiesterase, which may involve phosphatidylinositol 3-kinase and protein kinase B; (2) those leading to some of the effects of insulin on protein synthesis (formation of eukaryotic initiation factor-4F complex, S6 phosphorylation, and activation of eukaryotic elongation factor-2), which may involve phosphatidylinositol 3-kinase and p70 S6 kinase; and finally, (3) that leading to the activation of pyruvate dehydrogenase, which is unique in apparently not requiring activation of phosphatidylinositol 3-kinase.
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Affiliation(s)
- S K Moule
- Department of Biochemistry, University of Bristol School of Medical Sciences, UK
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32
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Lacasa D, Garcia E, Henriot D, Agli B, Giudicelli Y. Site-related specificities of the control by androgenic status of adipogenesis and mitogen-activated protein kinase cascade/c-fos signaling pathways in rat preadipocytes. Endocrinology 1997; 138:3181-6. [PMID: 9231766 DOI: 10.1210/endo.138.8.5290] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In rats, castration induces a complete defective adipose conversion of preadipocytes from the epididymal fat depots (Lacasa, D., B. Agli, D. Noynarol, and Y. Giudicelli, 1995, Endocrine 3: 789-793). The aim of this study was to establish the eventual site-specificity of this effect as well as the mechanisms involved. Therefore, the influence of androgenic status on the Fos protein induction and the Raf/mitogen-activated protein (MAP) kinase kinase (MEK)MAP cascade, which are all required for adipose conversion of preadipocytes, was compared in proliferating and differentiated preadipocytes from femoral sc and deep intraabdominal (epididymal and perirenal) fat depots. In epididymal and perirenal proliferating preadipocytes, increased proliferation due to castration is associated with increased MAP kinase activity. However, higher immunoreactive levels of the upstream activators of MAP kinase, Raf-1 and MEK, were observed only in epididymal cells. Moreover, in vivo testosterone treatment corrected the effects of castration on Raf-1 but not on MEK and MAP kinase. MAP kinase activity was decreased during the course of adipogenesis. In differentiated cells, MAP kinase activity showed variations according to the anatomical origin of preadipocytes but not to the androgenic status. In contrast, MEK and Raf-1 immunoreactive levels were both sensitive to androgenic status but were differently affected depending on cell origin. Finally, the defective adipogenesis seen in epididymal preadipocytes from castrated rats was associated with reduced Fos protein induction in these cells, an alteration which was partly corrected by testosterone-treatment. Taken together, these results suggest that androgenic status affects adipogenesis from deep intraabdominal preadipocytes through alterations of some components of the MAP kinase cascade/Fos signaling pathways.
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Affiliation(s)
- D Lacasa
- Service de Biochimie, INSERM CJF 94-02, Faculté de Medecine Paris-Ouest, Université René Descartes (Paris V) and Centre Hospitalier de Poissy, France
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33
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Kim HA, DeClue JE, Ratner N. cAMP-dependent protein kinase A is required for Schwann cell growth: Interactions between the cAMP and neuregulin/tyrosine kinase pathways. J Neurosci Res 1997. [DOI: 10.1002/(sici)1097-4547(19970715)49:2<236::aid-jnr12>3.0.co;2-z] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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34
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Wang HY, Goligorsky MS, Malbon CC. Temporal activation of Ca2+-calmodulin-sensitive protein kinase type II is obligate for adipogenesis. J Biol Chem 1997; 272:1817-21. [PMID: 8999866 DOI: 10.1074/jbc.272.3.1817] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Differentiation of 3T3-L1 embryonic fibroblasts to adipocytes in response to induction by dexamethasone and isobutylmethylxanthine is blocked by inhibitors of Ca2+-calmodulin-sensitive protein kinase type II, but not by inhibitors of protein kinase A or protein kinase C. CaM kinase II displays a biphasic increase in autonomous activity, rising after an initial transient peak from 1 to 15 h, declining at 24 h, followed by a sustained rise from 24 to 48 h, which is 2. 5-fold greater than basal values at induction of adipogenesis. Adipogenesis was blocked effectively by CaM kinase II inhibitors, either KN-62 or KN-93, if the inhibitors are introduced at 6 h and maintained until 12 h of induction of adipogenesis. Equally effective, however, is inhibition of CaM kinase II activity at 24-48 h after induction, during the later phase of autonomous CaM kinase activity. Inhibition of cultures with KN-62 or KN-93 either for 0 to 6 h or for 12 to 24 h failed to influence adipogenesis. Two temporally-distinct phases of CaM kinase II activation, either 6 to 12 h or 24 to 48 h, if inhibited with either KN-62 or KN-93, blocked the conversion to adipocytes. Thus, a biphasic activation of CaM kinase II is obligate for the progression of the embryonic fibroblasts to adipocytes. Inhibition of either phase of CaM kinase activity blocks adipogenesis and expression of several intermediate early gene products.
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Affiliation(s)
- H y Wang
- Department of Physiology & Biophysics, Diabetes & Metabolic Diseases Research Program, University Medical Center, SUNY/Stony Brook, Stony Brook, New York 11794, USA
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35
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Mitev V, Bayat-Sarmadi M, Lemnaouar M, Puissant C, Houdebine LM. The effect of prolactin on casein kinase II, MAP kinase and PKC in rabbit mammary cells and Nb2 rat lymphoid cells. Biochem Pharmacol 1996; 52:1719-27. [PMID: 8986134 DOI: 10.1016/s0006-2952(96)00523-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Prolactin induces milk protein gene expression in rabbit primary mammary cells without any concomitant cell multiplication. Prolactin or other lactogenic hormones is the major inducer of cell division in the rat lymphoid Nb2 cells. In Nb2 cells, prolactin also rapidly induces the expression of the c-myc gene, and beta-actin and stathmin gene expression is induced more slowly. The possible involvement of casein kinase II (CKII), mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) in these process is not well known. The present work was undertaken to evaluate the effect of prolactin on these protein kinases and to determine the possible involvement of these enzymes in the activity of several genes under the control of the hormone. In rabbit mammary cells, prolactin did not alter CKII activity but did transiently stimulate MAP kinase activity. Prolactin also stimulated Ca(2+)-independent PKC. This effect was visible after 10 min and was maintained for at least 24 hr. Staurosporine, an inhibitor of PKC and of several tyrosine kinases altered Ca(2+)-independent PKC only moderately. In contrast, GF 109203X, a potent and specific inhibitor of PKC, abrogated almost all PKC activity. Staurosporine, but not GF 109203X, prevented the induction of the casein gene by prolactin. In Nb2 cells, prolactin induced a slow stimulation of CKII activity. The hormone did not induce MAP kinase activity. Prolactin stimulated Ca(2+)-independent PKC over periods of 24 hr. GF 109203X, but not staurosporine, inhibited PKC activity, whereas staurosporine but not GF 109203X, inhibited the induction of Nb2 cell multiplication and the accumulation of c-myc, beta-actin and stathmin mRNAs. From these data, it can be concluded that (1) the stimulation of CKII by prolactin in Nb2 cells is concomitant with cell multiplication: (2) MAPK stimulation is not necessary for prolactin to induce Nb2 cell multiplication; and (3) PKC is stimulated in mammary and Nb2 cells, but this stimulation is not required for prolactin to stimulate casein, c-myc, beta-actin and stathmin gene expression and Nb2 cell division.
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Affiliation(s)
- V Mitev
- Unité de Différenciation Cellulaire, Institut National de la Recherche Argonomique, Jouy en Josas, France
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36
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Gilbreth M, Yang P, Wang D, Frost J, Polverino A, Cobb MH, Marcus S. The highly conserved skb1 gene encodes a protein that interacts with Shk1, a fission yeast Ste20/PAK homolog. Proc Natl Acad Sci U S A 1996; 93:13802-7. [PMID: 8943016 PMCID: PMC19432 DOI: 10.1073/pnas.93.24.13802] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/1996] [Accepted: 09/17/1996] [Indexed: 02/03/2023] Open
Abstract
The Shk1 protein kinase, a homolog of Saccharomyces cerevisiae Ste20 and mammalian p21Cdc42/Rac-activated kinases, is an essential component of a Ras- and Cdc42-dependent signaling cascade required for cell viability, normal morphology, and mitogen-activated protein kinase-mediated sexual responses in the fission yeast, Schizosaccharomyces pombe. To identify S. pombe proteins that modulate or mediate Shk1 functions, we conducted a two-hybrid screen for Shk1-interacting proteins. One of the genes identified as a result of this screen was skb1. We show that Skb1 interacts with a region of the N-terminal regulatory domain of Shk1 distinct from that to which Cdc42 binds, and that Shk1, Cdc42, and Skb1 are able to form a ternary complex in vivo. S.pombe cells carrying an skb1 null mutation are less elongate in morphology than wild-type cells and exhibit a moderate growth defect. The morphology defect of the skb1 deletion mutant is suppressed by overexpression of Shk1. Overexpression of Skb1 causes wild-type S. pombe cells to become hyperelongated. Additional genetic analyses described herein suggest that Skb1 is a component of the morphology control branch of the Ras signaling cascade in S. pombe and that it positively modulates Shk1 function. Homologs of Skb1 are encoded by open reading frames in the genomes of S. cerevisiae and Caenorhabditis elegans and by an uncharacterized human cDNA sequence. Thus, skb1 may be the first well-characterized member of a highly conserved family of genes encoding potential p21Cdc42/Rac-activated kinase regulators.
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Affiliation(s)
- M Gilbreth
- Department of Molecular Genetics, University of Texas M.D. Anderson Cancer Center, Houston 77030, USA
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37
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Waldmann V, Rabes HM. What's new in ras genes? Physiological role of ras genes in signal transduction and significance of ras gene activation in tumorigenesis. Pathol Res Pract 1996; 192:883-91. [PMID: 8950754 DOI: 10.1016/s0344-0338(96)80067-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Ras gene mutations have been found with variable prevalence in different tumor types. While during the past decade a lot of information has been accumulated on the frequency of ras oncogene activation in tumors, the last two years brought considerable progress in elucidating molecular mechanisms of signal transduction for which cellular ras proteins are key elements. They transmit signals from upstream tyrosine kinases to downstream serine/threonine kinases ultimately leading to changes of gene expression cytoskeletal architecture, cell-to-cell interactions and metabolism. These signalling pathways are of interest for the physiological regulation of proliferation and differentiation in normal, as well as in cancer tissue. Mutational activation of cellular ras genes to transforming oncogenes is thought to promote cell growth even in the absence of extracellular stimuli, and may thereby contribute to the initiation and/or progression of tumors.
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Affiliation(s)
- V Waldmann
- Institute of Pathology, University of Munich, Germany
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38
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Chen JM, Manolatos S, Brandt-Rauf PW, Murphy RB, Monaco R, Pincus MR. Computed three-dimensional structures for the ras-binding domain of the raf-p74 protein complexed with ras-p21 and with its suppressor protein, rap-1A. JOURNAL OF PROTEIN CHEMISTRY 1996; 15:511-8. [PMID: 8895097 DOI: 10.1007/bf01908532] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The three-dimensional structures of the ras-p21 protein and its protein inhibitor, rap-1A, have been computed bound to the ras-binding domain, RBD (residues 55-131), of the raf-p74 protein, a critical target protein of ras-p21 in the ras-induced mitogenic signal transduction pathway. The coordinates of RBD have been reconstructed from the stereoview of an X-ray crystal structure of this domain bound to rap-1A and have been subjected to energy minimization. The energy-minimized structures of both ras-p21 and rap-1A, obtained in previous studies, have been docked against RBD, using the stereo figure of the RBD-rap-1A complex, based on a six-step procedure. The final energy-minimized structure of rap-1A-RBD is identical to the X-ray crystal structure. Comparison of the ras-p21- and rap-1A-RBD complexes reveals differences in the structures of effector domains of ras-p21 and rap-1a, including residues 32-47, a domain that directly interacts with RBD, 60-66, 96-110, involved in the interaction of ras-p21 with jun kinase (JNK) and jun protein, and 115-126, involved in the interaction of p21 with JNK. The structure of the RBD remained the same in both complexes with the exception of small deviations in its beta-2 binding loop (residues 63-71) and residues 89-91, also involved in binding to rap-1A. The results suggest that the binding of these two proteins to RBD may allow them to interact with other cellular target proteins such as JNK and jun.
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Affiliation(s)
- J M Chen
- Dupont Agricultural Products, Stein-Haskell Research Center, Newark, Delaware 19714, USA
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39
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Monia BP, Johnston JF, Geiger T, Muller M, Fabbro D. Antitumor activity of a phosphorothioate antisense oligodeoxynucleotide targeted against C-raf kinase. Nat Med 1996; 2:668-75. [PMID: 8640558 DOI: 10.1038/nm0696-668] [Citation(s) in RCA: 364] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Substantial evidence exists supporting a direct role for raf kinases in the development and maintenance of certain human malignancies. Here we test the potential of phosphorothioate antisense oligodeoxynucleotides targeted against human C-raf-1 kinase to specifically inhibit C-raf-1 kinase gene expression and tumor progression in cell culture and in vivo, using human tumor xenograft mouse models. Treatment of human tumor cells with appropriate phosphorothioate antisense oligodeoxynucleotides led to specific inhibition of C-raf kinase gene expression in cell culture and in vivo at well-tolerated doses. Moreover, oligodeoxynucleotide treatment resulted in potent antiproliferative effects in cell culture and potent antitumor effects in vivo against a variety of tumor types that were highly consistent with an antisense mechanism of action for these compounds. These studies strongly suggest that antisense inhibitors targeted against C-raf-1 kinase may be of considerable value as antineoplastic agents that display activity against a wide spectrum of tumor types at well-tolerated doses.
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MESH Headings
- Animals
- Antineoplastic Agents/chemistry
- Antineoplastic Agents/pharmacology
- Base Sequence
- Carcinoma/drug therapy
- Carcinoma/pathology
- Cell Division/drug effects
- Dose-Response Relationship, Drug
- Gene Expression Regulation, Neoplastic
- Humans
- Lung Neoplasms/drug therapy
- Lung Neoplasms/pathology
- Mice
- Mice, Inbred BALB C
- Molecular Sequence Data
- Neoplasms, Experimental/drug therapy
- Oligodeoxyribonucleotides, Antisense
- Oligonucleotides, Antisense/chemistry
- Oligonucleotides, Antisense/pharmacology
- Protein Serine-Threonine Kinases/drug effects
- Proto-Oncogene Proteins/drug effects
- Proto-Oncogene Proteins c-raf
- RNA, Messenger
- Thionucleotides/chemistry
- Thionucleotides/pharmacology
- Transplantation, Heterologous
- Tumor Cells, Cultured/drug effects
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Affiliation(s)
- B P Monia
- Department of Molecular Pharmacology, Isis Pharmaceuticals, Carlsbad, California 92008, USA
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40
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Wixler V, Smola U, Schuler M, Rapp U. Differential regulation of Raf isozymes by growth versus differentiation inducing factors in PC12 pheochromocytoma cells. FEBS Lett 1996; 385:131-7. [PMID: 8647237 DOI: 10.1016/0014-5793(96)00363-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
PC12 pheochromocytoma cells possess four known MEK activators: A-, B-, c-Raf-1 and MEKK. In order to examine whether differentiation factors or growth factors have a Raf isozyme preference for activation of the mitogenic cytoplasmic Raf-MEK-MAPK protein kinase cascade, the activation kinetics of these enzymes in response to epidermal growth factor (EGF) and nerve growth factor (NGF) were compared. An initial activation of all three Raf kinases was noticed, but only A- and B-Raf showed sustained activation by NGF, which was not seen after EGF treatment. Furthermore, expression of oncogenic versions of all three Raf kinases as well, as a potentially Raf-independent MEK activator, v-Mos, leads to activation of MAPK and to differentiation of PC12 cells. These data suggest a differential regulation of Raf kinases and that probably no alternative Raf substrates are involved in differentiation processes of PC12 cells.
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Affiliation(s)
- V Wixler
- Institute of Medical Radiation and Cell Research, Bayerisch, Julius-Maximillians-Universität, Würzburg, Germany
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41
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Lee T, Feig L, Montell DJ. Two distinct roles for Ras in a developmentally regulated cell migration. Development 1996; 122:409-18. [PMID: 8625792 DOI: 10.1242/dev.122.2.409] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Receptor tyrosine kinases have been shown to promote cell movement in a variety of systems. The Ras protein, a well-documented downstream effector for receptor tyrosine kinases, may contribute to receptor tyrosine kinase-mediated motility. In the present study, we have examined the role of Ras in the migration of a small subset of follicle cells, known as the border cells, during Drosophila oogenesis. A dominant-negative Ras protein inhibited cell migration when expressed specifically in border cells during the period when these cells normally migrate. When expressed prior to migration, dominant-negative Ras promoted premature initiation of migration. Conversely, expression of constitutively active Ras prior to migration resulted in a significant delay in the initiation step. Furthermore, the defect in initiation of border cell migration found in slbo1, a mutation at the locus that encodes Drosophila C/EBP, was largely rescued by reducing Ras activity in border cells prior to migration. Taken together, these observations indicate that Ras activity plays two distinct roles in the border cells: (1) reduction in Ras activity promotes the initiation of that migration process and (2) Ras activity is required during border cell migration. We further examined the possible involvement of two downstream effectors of Ras in border cell migration. Raf activity was dispensable to border cell migration while reduced Ral activity inhibited initiation. We therefore suggest that Ras plays a critical role in the dynamic regulation of border cell migration via a Raf-independent pathway.
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Affiliation(s)
- T Lee
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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42
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PDGF and FGF receptors in health and disease. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s1874-5687(96)80009-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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43
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Fusco A, Vecchio G, Dathan NA, Carlomagno F, Di Fiore PP, Santoro M. Intracellular Signaling by the ret Tyrosine Kinase. ACTA ACUST UNITED AC 1996. [DOI: 10.1007/978-3-662-21948-5_3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
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44
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Polverino A, Frost J, Yang P, Hutchison M, Neiman AM, Cobb MH, Marcus S. Activation of mitogen-activated protein kinase cascades by p21-activated protein kinases in cell-free extracts of Xenopus oocytes. J Biol Chem 1995; 270:26067-70. [PMID: 7592806 DOI: 10.1074/jbc.270.44.26067] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
In the evolutionarily distant yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, genetic evidence suggests that activation of pheromone-induced mitogen-activated protein kinase (MAPK) cascades involves the function of the p21cdc42/racl-activated protein kinases (PAKs) Ste20 and Shk1, respectively. In this report, we show that purified Ste20 and Shk1 were each capable of inducing p42MAPK activation in cell-free extracts of Xenopus laevis oocytes, while a mammalian Ste20/Shk1-related protein kinase, p65pak (Pak1), did not induce activation of p42MAPK. In contrast to p42MAPK, activation of JNK/SAPK in Xenopus oocyte extracts was induced by both the yeast Ste20 and Shk1 kinases, as well as by mammalian Pak1. Our results demonstrate that MAPK cascades that are responsive to PAKs are conserved in higher eukaryotes and suggest that distinct PAKs may regulate distinct MAPK modules.
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Affiliation(s)
- A Polverino
- Department of Protein Structure, Amgen Inc., Thousand Oaks, California 91320-1789, USA
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45
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Crespo P, Cachero TG, Xu N, Gutkind JS. Dual effect of beta-adrenergic receptors on mitogen-activated protein kinase. Evidence for a beta gamma-dependent activation and a G alpha s-cAMP-mediated inhibition. J Biol Chem 1995; 270:25259-65. [PMID: 7559665 DOI: 10.1074/jbc.270.42.25259] [Citation(s) in RCA: 189] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The enzymatic activity of mitogen-activated protein kinases (MAP kinases) increases in response to agents acting on a variety of cell surface receptors, including receptors linked to heterotrimeric G proteins of the Gi and Gq family. Recently, it has been shown that stimulation of beta-adrenergic receptors, which are typical of those that act through Gs to activate adenylyl cyclases, potently activates MAP kinases in the heart, resulting in the hypertrophy of the cardiac muscle (Lazou, A., Bogoyevitch, M.A., Clerk, A., Fuller, S.J., Marshall, C.J., and Sudgen, P.H. (1994) Circ. Res. 75, 938-941). We have observed that exposure of COS-7 cells to a beta-adrenergic agonist, isoproterenol, raises intracellular levels of cAMP and effectively activates protein kinase A (PKA) and an epitope-tagged MAP kinase. However, MAP kinase stimulation by isoproterenol was neither mimicked by expression of an activated mutant of G alpha s, nor by treatment with PKA-stimulating agents. Moreover, pretreatment of COS-7 with a permeable cAMP analog, 8-Br-cAMP, markedly decreased MAP kinase activation by either isoproterenol or epidermal growth factor. Thus, in COS-7 cells cAMP and PKA do not appear to mediate MAP kinase activation by beta-adrenergic receptors. Signaling from beta-adrenergic receptors to MAP kinase was inhibited by transfection of a chimeric molecule consisting of the CD8 receptor and the carboxyl terminus of the beta-adrenergic receptor kinase, which includes the beta gamma-binding domain. MAP kinase activation by isoproterenol was not affected by depletion of protein kinase C, but it was completely abolished by expression of Ras-inhibiting molecules. We conclude that signaling from beta-adrenergic receptors to MAP kinase involves an activating signal mediated by beta gamma subunits acting on a Ras-dependent pathway and a G alpha s-induced inhibitory signal mediated by cAMP and PKA. The balance between these two opposing mechanisms of regulation would be expected to control the MAP kinase response to beta-adrenergic agonists as well as to other biologically active agents known to act on Gs coupled receptors, including a number of hormones, neurotransmitters, and lipid mediators.
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Affiliation(s)
- P Crespo
- Molecular Signaling Unit, NIDR, National Institutes of Health, Bethesda, Maryland 20892, USA
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46
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Indolfi C, Avvedimento EV, Rapacciuolo A, Di Lorenzo E, Esposito G, Stabile E, Feliciello A, Mele E, Giuliano P, Condorelli G. Inhibition of cellular ras prevents smooth muscle cell proliferation after vascular injury in vivo. Nat Med 1995; 1:541-5. [PMID: 7585120 DOI: 10.1038/nm0695-541] [Citation(s) in RCA: 165] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Proliferation of smooth muscle cells of the arterial wall in response to local injury is an important aetiologic factor of vascular proliferative disorders such as atherosclerosis and restenosis after angioplasty. Ras proteins are key transducers of mitogenic signals from membrane to nucleus in many cell types. We investigated the role of ras proteins in the vascular response to arterial injury by inactivating cellular ras of rats in which the common carotid artery was subjected to balloon injury. DNA vectors expressing ras transdominant negative mutants, which interfere with ras function, reduced neointimal formation after injury. Our results indicate a key role for ras in smooth muscle cell proliferation and show that the local delivery of transdominant negative mutants of ras in vivo might prevent some of the acute vascular injury caused by balloon injury.
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MESH Headings
- Animals
- Carotid Artery Injuries
- Carotid Artery, Common/drug effects
- Carotid Artery, Common/pathology
- Catheterization/adverse effects
- Cell Division/drug effects
- Cell Division/genetics
- DNA, Recombinant/genetics
- DNA, Recombinant/therapeutic use
- Genes, ras
- Genetic Therapy
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/injuries
- Muscle, Smooth, Vascular/pathology
- Point Mutation
- Protein Serine-Threonine Kinases/antagonists & inhibitors
- Protein Serine-Threonine Kinases/genetics
- Proto-Oncogene Proteins/antagonists & inhibitors
- Proto-Oncogene Proteins/genetics
- Proto-Oncogene Proteins c-raf
- Proto-Oncogene Proteins p21(ras)/antagonists & inhibitors
- Proto-Oncogene Proteins p21(ras)/genetics
- Rats
- Rats, Wistar
- Recombinant Fusion Proteins
- Transfection
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Affiliation(s)
- C Indolfi
- Cattedra di Cardiologia, Università degli Studi di Napoli Federico II, Italy
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47
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Reuter CW, Catling AD, Jelinek T, Weber MJ. Biochemical analysis of MEK activation in NIH3T3 fibroblasts. Identification of B-Raf and other activators. J Biol Chem 1995; 270:7644-55. [PMID: 7706312 DOI: 10.1074/jbc.270.13.7644] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Numerous potential activators of MEK have been identified, including c-Raf-1, B-Raf, c-Mos, and a family of MEK kinases. However, little information gives insight into the activators actually utilized in vivo. To address this, we have used column chromatography and a coupled MEK activation assay to identify in NIH3T3 cells, two major MEK activators, and a third insulin-specific activator. The first MEK activator has an apparent M(r) of 40,000-50,000, was immunologically distinct from A-Raf, B-Raf, c-Raf-1, c-MEKK, c-Mos, MEK1, and MEK2, and was rapidly activated by serum, platelet-derived growth factor (PDGF), insulin, thrombin, and phorbol ester. The second MEK activator was identified as B-Raf. Activation of 93-95 kDa B-Raf was observed in column fractions and B-Raf immunoprecipitates from cytosolic and particulate fractions after stimulation with serum or PDGF, but not insulin. c-Raf-1 from cytosol did not exhibit MEK activator activity; however, c-Raf-1 immunoprecipitates from the particulate fraction revealed MEK activator activity that was enhanced after stimulation with PDGF or phorbol ester, but not serum or insulin. Both c-Mos and c-MEKK were present in NIH3T3 fibroblasts but did not show MEK activator activity. These data provide direct evidence that 93-95-kDa B-Raf isozymes and an unidentified 40-50-kDa MEK activator are major agonist-specific MEK activators in NIH3T3 fibroblasts.
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Affiliation(s)
- C W Reuter
- Department of Microbiology, University of Virginia Health Sciences Center, School of Medicine, Charlottesville 22908, USA
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48
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White MA, Nicolette C, Minden A, Polverino A, Van Aelst L, Karin M, Wigler MH. Multiple Ras functions can contribute to mammalian cell transformation. Cell 1995; 80:533-41. [PMID: 7867061 DOI: 10.1016/0092-8674(95)90507-3] [Citation(s) in RCA: 575] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We have developed a generalized approach, using two hybrid interactions, to isolate Ha-Ras effector loop mutations that separate the ability of Ha-Ras to interact with different downstream effectors. These mutations attenuate or eliminate Ha-ras(G12V) transformation of mammalian cells, but retain complementary activity, as demonstrated by synergistic induction of foci of growth-transformed cells, and by the ability to activate different downstream components. The transformation defect of Ha-ras(G12V, E37G) is rescued by a mutant, raf1, that restores interaction. These results indicate that multiple cellular components, including Raf1, are activated by Ha-Ras and contribute to Ha-Ras-induced mammalian cell transformation.
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Affiliation(s)
- M A White
- Cold Spring Harbor Laboratory, New York 11724
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49
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Denton RM, Tavaré JM. Does mitogen-activated-protein kinase have a role in insulin action? The cases for and against. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 227:597-611. [PMID: 7867619 DOI: 10.1111/j.1432-1033.1995.tb20179.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The discovery of the mitogen-activated protein (MAP) kinase family of protein kinases has sparked off an intensive effort to elucidate their role in the regulation of many cellular processes. These protein kinases were originally identified based on their rapid activation by insulin. In this review we concentrate on examining the evidence for and against a role for the MAP kinases Erk-1 and Erk-2 in mediating the effects of insulin. While there is good evidence in favour of a direct role for MAP kinase in the growth-promoting effects of insulin and the regulation of Glut-1 and c-fos expression, and AP-1 transcriptional complex activity, this is by no means conclusive. MAP kinase may also play a role in the control of mRNA translation by insulin. On the other hand, the evidence suggests that MAP kinase is not sufficient for the acute regulation of glucose transport (Glut-4 translocation), glycogen synthesis, acetyl-CoA carboxylase or pyruvate dehydrogenase activity. The findings suggest that insulin may utilise at least three distinct signalling pathways which do not involve MAP kinase.
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Affiliation(s)
- R M Denton
- Department of Biochemistry, School of Medical Sciences, University of Bristol, England
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50
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Peraldi P, Frödin M, Barnier JV, Calleja V, Scimeca JC, Filloux C, Calothy G, Van Obberghen E. Regulation of the MAP kinase cascade in PC12 cells: B-Raf activates MEK-1 (MAP kinase or ERK kinase) and is inhibited by cAMP. FEBS Lett 1995; 357:290-6. [PMID: 7835430 DOI: 10.1016/0014-5793(94)01376-c] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In PC12 cells, cAMP stimulates the MAP kinase pathway by an unknown mechanism. Firstly, we examined the role of calcium ion mobilization and of protein kinase C in cAMP-stimulated MAP kinase activation. We show that cAMP stimulates p44mapk independently of these events. Secondly, we studied the role of B-Raf in this process. We observed that NGF, PMA and cAMP induce the phosphorylation of B-Raf as well as an upward shift in its electrophoretic mobility. We show that B-Raf is activated following NGF and PMA treatment of PC12 cells, and that it can phosphorylate and activate MEK-1. However, cAMP inhibits B-Raf autokinase activity as well as its ability to phosphorylate and activate MEK-1. This inhibition is likely to be due to a direct effect since we found that PKA phosphorylates B-Raf in vitro. Further, we show that B-Raf binds to p21ras, but more important, this binding to p21ras is virtually abolished with B-Raf from PC12 cells treated with CPT-cAMP. Hence, these data indicate that the PKA-mediated phosphorylation of B-Raf hampers its interaction with p21ras, which is responsible for the PKA-mediated decrease in B-Raf activity. Finally, our work suggests that in PC12 cells, cAMP stimulates MAP kinase through the activation of an unidentified MEK kinase and/or the inhibition of a MEK phosphatase.
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Affiliation(s)
- P Peraldi
- INSERM U 145, Faculté de Médecine, Nice, France
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