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Console L, Scalise M, Salerno S, Scanga R, Giudice D, De Bartolo L, Tonazzi A, Indiveri C. N-glycosylation is crucial for trafficking and stability of SLC3A2 (CD98). Sci Rep 2022; 12:14570. [PMID: 36028562 PMCID: PMC9418156 DOI: 10.1038/s41598-022-18779-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 08/18/2022] [Indexed: 11/30/2022] Open
Abstract
The type II glycoprotein CD98 (SLC3A2) is a membrane protein with pleiotropic roles in cells, ranging from modulation of inflammatory processes, host–pathogen interactions to association with membrane transporters of the SLC7 family. The recent resolution of CD98 structure in complex with LAT1 showed that four Asn residues, N365, N381, N424, N506, harbour N-glycosylation moieties. Then, the role of N-glycosylation on CD98 trafficking and stability was investigated by combining bioinformatics, site-directed mutagenesis and cell biology approach. Single, double, triple and quadruple mutants of the four Asn exhibited altered electrophoretic mobility, with apparent molecular masses from 95 to 70 kDa. The quadruple mutant displayed a single band of 70 kDa corresponding to the unglycosylated protein. The presence in the membrane and the trafficking of CD98 were evaluated by a biotinylation assay and a brefeldin assay, respectively. Taken together, the results highlighted that the quadruple mutation severely impaired both the stability and the trafficking of CD98 to the plasma membrane. The decreased presence of CD98 at the plasma membrane, correlated with a lower presence of LAT1 (SLC7A5) and its transport activity. This finding opens new perspectives for human therapy. Indeed, the inhibition of CD98 trafficking would act synergistically with LAT1 inhibitors that are under clinical trial for anticancer therapy.
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Affiliation(s)
- Lara Console
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via Bucci 4C, 87036, Arcavacata di Rende, Italy
| | - Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via Bucci 4C, 87036, Arcavacata di Rende, Italy
| | - Simona Salerno
- CNR Institute on Membrane Technology, National Research Council of Italy (CNR-ITM), Via P. Bucci, cubo 17/C, 87036, Rende, Italy
| | - Raffaella Scanga
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via Bucci 4C, 87036, Arcavacata di Rende, Italy
| | - Deborah Giudice
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via Bucci 4C, 87036, Arcavacata di Rende, Italy
| | - Loredana De Bartolo
- CNR Institute on Membrane Technology, National Research Council of Italy (CNR-ITM), Via P. Bucci, cubo 17/C, 87036, Rende, Italy
| | - Annamaria Tonazzi
- CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), Via Amendola 122/O, 70126, Bari, Italy
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Via Bucci 4C, 87036, Arcavacata di Rende, Italy. .,CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), Via Amendola 122/O, 70126, Bari, Italy.
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Zhang Y, Hu H, Liu W, Yan SM, Li Y, Tan L, Chen Y, Liu J, Peng Z, Yuan Y, Huang W, Yu F, He X, Li B, Zhang H. Amino acids and RagD potentiate mTORC1 activation in CD8 + T cells to confer antitumor immunity. J Immunother Cancer 2021; 9:e002137. [PMID: 33883257 PMCID: PMC8061841 DOI: 10.1136/jitc-2020-002137] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/17/2021] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND In the tumor microenvironment, tumor cells are able to suppress antitumor immunity by competing for essential nutrients, including amino acids. However, whether amino acid depletion modulates the activity of CD8+ tumor-infiltrating lymphocytes (TILs) is unclear. METHOD In this study, we evaluated the roles of amino acids and the Rag complex in regulating mammalian target of rapamycin complex 1 (mTORC1) signaling in CD8+ TILs. RESULTS We discovered that the Rag complex, particularly RagD, was crucial for CD8+ T-cell antitumor immunity. RagD expression was positively correlated with the antitumor response of CD8+ TILs in both murine syngeneic tumor xenografts and clinical human colon cancer samples. On RagD deficiency, CD8+ T cells were rendered more dysfunctional, as demonstrated by attenuation of mTORC1 signaling and reductions in proliferation and cytokine secretion. Amino acids maintained RagD-mediated mTORC1 translocation to the lysosome, thereby achieving maximal mTORC1 activity in CD8+ T cells. Moreover, the limited T-cell access to leucine (LEU), overshadowed by tumor cell amino acid consumption, led to impaired RagD-dependent mTORC1 activity. Finally, combined with antiprogrammed cell death protein 1 antibody, LEU supplementation improved T-cell immunity in MC38 tumor-bearing mice in vivo. CONCLUSION Our results revealed that robust signaling of amino acids by RagD and downstream mTORC1 signaling were crucial for T-cell receptor-initiated antitumor immunity. The characterization the role of RagD and LEU in nutrient mTORC1 signaling in TILs might suggest potential therapeutic strategies based on the manipulation of RagD and its upstream pathway.
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Affiliation(s)
- Yiwen Zhang
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Hongrong Hu
- Department of Biochemistry, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
- Sun Yat-sen University Cancer Center, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Weiwei Liu
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Shu-Mei Yan
- Sun Yat-sen University Cancer Center, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Yuzhuang Li
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Likai Tan
- Institute of Immunology, Hannover Medical School, Hannover, Niedersachsen, Germany
| | - Yingshi Chen
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Jun Liu
- School of Medicine, Sun Yat-sen University, Shenzhen, China
| | - Zhilin Peng
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Yaochang Yuan
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Wenjing Huang
- Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong, China
| | - Fei Yu
- Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong, China
| | - Xin He
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Bo Li
- Department of Biochemistry, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Hui Zhang
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
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Almutairi SM, Ali AK, He W, Yang DS, Ghorbani P, Wang L, Fullerton MD, Lee SH. Interleukin-18 up-regulates amino acid transporters and facilitates amino acid-induced mTORC1 activation in natural killer cells. J Biol Chem 2019; 294:4644-4655. [PMID: 30696773 DOI: 10.1074/jbc.ra118.005892] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 01/16/2019] [Indexed: 12/29/2022] Open
Abstract
Upon inflammation, natural killer (NK) cells undergo metabolic changes to support their high energy demand for effector function and proliferation. The metabolic changes are usually accompanied by an increase in the expression of nutrient transporters, leading to increased nutrient uptake. Among various cytokines inducing NK cell proliferation, the mechanisms underlying the effect of interleukin (IL)-18 in promoting NK cell proliferation are not completely understood. Here, we demonstrate that IL-18 is a potent cytokine that can enhance the expression of the nutrient transporter CD98/LAT1 for amino acids independently of the mTORC1 pathway and thereby induce a dramatic metabolic change associated with increased proliferation of NK cells. Notably, treatment of IL-18-stimulated NK cells with leucine activates the metabolic sensor mTORC1, indicating that the high expression of amino acid transporters induces amino acid-driven mTORC1 activation. Inhibition of the amino acid transporter CD98/LAT1 abrogated the leucine-driven mTORC1 activation and reduced NK cell effector function. Taken together, our study identified a novel role of IL-18 in up-regulating nutrient transporters on NK cells and thereby inducing metabolic changes, including the mTORC1 activation by amino acids.
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Affiliation(s)
- Saeedah Musaed Almutairi
- From the Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and.,Botany and Microbiology Department, College of Sciences, King Saud University, Riyadh 11451, Saudi Arabia
| | - Alaa Kassim Ali
- From the Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - William He
- From the Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Doo-Seok Yang
- From the Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Peyman Ghorbani
- From the Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Lisheng Wang
- From the Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Morgan D Fullerton
- From the Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
| | - Seung-Hwan Lee
- From the Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada and
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Ablack JNG, Metz PJ, Chang JT, Cantor JM, Ginsberg MH. Ubiquitylation of CD98 limits cell proliferation and clonal expansion. J Cell Sci 2015; 128:4273-8. [PMID: 26493331 PMCID: PMC4712820 DOI: 10.1242/jcs.178129] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 10/19/2015] [Indexed: 01/02/2023] Open
Abstract
CD98 heavy chain (SLC3A2) facilitates lymphocyte clonal expansion that enables adaptive immunity; however, increased expression of CD98 is also a feature of both lymphomas and leukemias and represents a potential therapeutic target in these diseases. CD98 is transcriptionally regulated and ectopic expression of the membrane-associated RING-CH (MARCH) E3 ubiquitin ligases MARCH1 or MARCH8 leads to ubiquitylation and lysosomal degradation of CD98. Here, we examined the potential role of ubiquitylation in regulating CD98 expression and cell proliferation. We report that blocking ubiquitylation by use of a catalytically inactive MARCH or by creating a ubiquitylation-resistant CD98 mutant, prevents MARCH-induced CD98 downregulation in HeLa cells. March1-null T cells display increased CD98 expression. Similarly, T cells expressing ubiquitylation-resistant CD98 manifest increased proliferation in vitro and clonal expansion in vivo. Thus, ubiquitylation and the resulting downregulation of CD98 can limit cell proliferation and clonal expansion.
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Affiliation(s)
- Jailal N G Ablack
- Department of Medicine, University of California San Diego, La Jolla, CA 92093-0726, USA
| | - Patrick J Metz
- Department of Medicine, University of California San Diego, La Jolla, CA 92093-0726, USA
| | - John T Chang
- Department of Medicine, University of California San Diego, La Jolla, CA 92093-0726, USA
| | - Joseph M Cantor
- Department of Medicine, University of California San Diego, La Jolla, CA 92093-0726, USA
| | - Mark H Ginsberg
- Department of Medicine, University of California San Diego, La Jolla, CA 92093-0726, USA
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5
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Sinclair LV, Rolf J, Emslie E, Shi YB, Taylor PM, Cantrell DA. Control of amino-acid transport by antigen receptors coordinates the metabolic reprogramming essential for T cell differentiation. Nat Immunol 2013; 14:500-8. [PMID: 23525088 PMCID: PMC3672957 DOI: 10.1038/ni.2556] [Citation(s) in RCA: 648] [Impact Index Per Article: 58.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 01/24/2013] [Indexed: 12/13/2022]
Abstract
T lymphocytes must regulate nutrient uptake to meet the metabolic demands of an immune response. Here we show that the intracellular supply of large neutral amino acids (LNAAs) in T cells was regulated by pathogens and the T cell antigen receptor (TCR). T cells responded to antigen by upregulating expression of many amino-acid transporters, but a single System L ('leucine-preferring system') transporter, Slc7a5, mediated uptake of LNAAs in activated T cells. Slc7a5-null T cells were unable to metabolically reprogram in response to antigen and did not undergo clonal expansion or effector differentiation. The metabolic catastrophe caused by loss of Slc7a5 reflected the requirement for sustained uptake of the LNAA leucine for activation of the serine-threonine kinase complex mTORC1 and for expression of the transcription factor c-Myc. Control of expression of the System L transporter by pathogens is thus a critical metabolic checkpoint for T cells.
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Affiliation(s)
- Linda V Sinclair
- Division of Cell Signalling and Immunology, University of Dundee, Dundee, UK
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Roy SG, Stevens MW, So L, Edinger AL. Reciprocal effects of rab7 deletion in activated and neglected T cells. Autophagy 2013; 9:1009-23. [PMID: 23615463 DOI: 10.4161/auto.24468] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Mouse models lacking proteins essential for autophagosome formation have demonstrated that autophagy plays a critical role in T cell development and activation. To better understand the function of autophagy in quiescent and activated lymphocytes, we have generated a mouse deficient in rab7 selectively in T cells and compared the effects of blocking autophagy at an early (atg5(-/-)) or late (rab7(-/-)) stage on T cell biology. rab7(-/-) murine embryonic fibroblasts (MEFs) and T cells generated from these mice exhibit a profound block in autophagosome degradation and are as sensitive as atg5(-/-) cells to extracellular nutrient limitation. Rab7(flox/flox)CD4-Cre(+) mice lacking the RAB7 protein in both CD4 and CD8 T cells had reduced numbers of peripheral T cells, but this defect was not as severe as in Atg5(flox/flox)CD4-Cre(+) mice despite efficient rab7 deletion and inhibition of autophagic flux. This difference may stem from the reduced ROS generation and enhanced survival of rab7(-/-) T cells compared with wild-type and atg5(-/-) T cells in the absence of cytokine stimulation. rab7(-/-) and atg5(-/-) T cells exhibited similar defects in proliferation both following antibody-mediated T cell receptor (TCR) cross-linking and using a more physiologic activation protocol, allogeneic stimulation. Interestingly, autophagy was not required to provide building blocks for the upregulation of nutrient transporter proteins immediately following activation. Together, these studies suggest that autophagosome degradation is required for the survival of activated T cells, but that loss of rab7 is better tolerated in naïve T cells than the loss of atg5.
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Affiliation(s)
- Saurabh Ghosh Roy
- Department of Developmental and Cell Biology; University of California, Irvine; Irvine, CA USA
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Abstract
mTOR is an evolutionarily conserved serine/threonine kinase that plays a critical role in cell growth and metabolism by sensing different environmental cues. There is a growing appreciation of mTOR in immunology for its role in integrating diverse signals from the immune microenvironment and coordinating the functions of immune cells and their metabolism. In CD8 T cells, mTOR has shown to influence cellular commitment to effector versus memory programming; in CD4 T cells, mTOR integrates environmental cues that instruct effector cell differentiation. In this review, we summarize and discuss recent advances in the field, with a focus on the mechanisms through which mTOR regulates cellular and humoral immunity. Further understanding will enable the manipulation of mTOR signaling to direct the biological functions of immune cells, which holds great potential for improving immune therapies and vaccination against infections and cancer.
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8
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Cantor JM, Ginsberg MH. CD98 at the crossroads of adaptive immunity and cancer. J Cell Sci 2012; 125:1373-82. [PMID: 22499670 DOI: 10.1242/jcs.096040] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Adaptive immunity, a vertebrate specialization, adds memory and exquisite specificity to the basic innate immune responses present in invertebrates while conserving metabolic resources. In adaptive immunity, antigenic challenge requires extremely rapid proliferation of rare antigen-specific lymphocytes to produce large, clonally expanded effector populations that neutralize pathogens. Rapid proliferation and resulting clonal expansion are dependent on CD98, a protein whose well-conserved orthologs appear restricted to vertebrates. Thus, CD98 supports lymphocyte clonal expansion to enable protective adaptive immunity, an advantage that could account for the presence of CD98 in vertebrates. CD98 supports lymphocyte clonal expansion by amplifying integrin signals that enable proliferation and prevent apoptosis. These integrin-dependent signals can also provoke cancer development and invasion, anchorage-independence and the rapid proliferation of tumor cells. CD98 is highly expressed in many cancers and contributes to formation of tumors in experimental models. Strikingly, vertebrates, which possess highly conserved CD98 proteins, CD98-binding integrins and adaptive immunity, also display propensity towards invasive and metastatic tumors. In this Commentary, we review the roles of CD98 in lymphocyte biology and cancer. We suggest that the CD98 amplification of integrin signaling in adaptive immunity provides survival benefits to vertebrates, which, in turn, bear the price of increased susceptibility to cancer.
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Affiliation(s)
- Joseph M Cantor
- Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA
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9
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Homeostatic and innate immune responses: role of the transmembrane glycoprotein CD98. Cell Mol Life Sci 2012; 69:3015-26. [PMID: 22460579 DOI: 10.1007/s00018-012-0963-z] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2011] [Revised: 02/14/2012] [Accepted: 03/12/2012] [Indexed: 12/11/2022]
Abstract
The transmembrane glycoprotein CD98 is a potential regulator of multiple functions, including integrin signaling and amino acid transport. Abnormal expression or function of CD98 and disruption of the interactions between CD98 and its binding partners result in defects in cell homeostasis and immune responses. Indeed, expression of CD98 has been correlated with diseases such as inflammation and tumor metastasis. Modulation of CD98 expression and/or function therefore represents a promising therapeutic strategy for the treatment and prevention of such pathologies. Herein, we review the role of CD98 with focus on its functional importance in homeostasis and immune responses, which could help to better understand the pathogenesis of CD98-associated diseases.
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Nguyen HTT, Dalmasso G, Yan Y, Laroui H, Dahan S, Mayer L, Sitaraman SV, Merlin D. MicroRNA-7 modulates CD98 expression during intestinal epithelial cell differentiation. J Biol Chem 2009; 285:1479-89. [PMID: 19892711 DOI: 10.1074/jbc.m109.057141] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The transmembrane glycoprotein CD98 regulates multiple cellular functions, including extracellular signaling, epithelial cell adhesion/polarity, amino acid transport, and cell-cell interactions. MicroRNAs post-transcriptionally regulate gene expression, thereby functioning as modulators of numerous cellular processes, such as cell differentiation, proliferation, and apoptosis. Here, we investigated if microRNAs regulate CD98 expression during intestinal epithelial cell differentiation and inflammation. We found that microRNA-7 repressed CD98 expression in Caco2-BBE cells by directly targeting the 3'-untranslated region of human CD98 mRNA. Expression of CD98 was decreased, whereas that of microRNA-7 was increased in well-differentiated Caco2-BBE cells compared with undifferentiated cells. Undifferentiated crypt cells isolated from mouse jejunum showed higher CD98 levels and lower levels of mmu-microRNA-706, a murine original microRNA candidate for CD98, than well-differentiated villus cells. Importantly, microRNA-7 decreased Caco2-BBE cell attachment on laminin-1, and CD98 overexpression recovered this inhibition, suggesting that microRNA-7 modulates epithelial cell adhesion to extracellular matrix, which in turn could affect proliferation and differentiation during the migration of enterocytes across the crypt-villus axis, by regulating CD98 expression. In a pathological context, the pro-inflammatory cytokine interleukin 1-beta increased CD98 expression in Caco2-BBE cells by decreasing microRNA-7 levels. Consistent with the in vitro findings, microRNA-7 levels were decreased in actively inflamed Crohn disease colonic tissues, where CD98 expression was up-regulated, compared with normal tissues. Together, these results reveal a novel mechanism underlying regulation of CD98 expression during patho-physiological states. This study raises microRNAs as a promising target for therapeutic modulations of CD98 expression in intestinal inflammatory disorders.
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Affiliation(s)
- Hang Thi Thu Nguyen
- Department of Medicine, Division of Digestive Diseases, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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Jones RG, Thompson CB. Tumor suppressors and cell metabolism: a recipe for cancer growth. Genes Dev 2009; 23:537-48. [PMID: 19270154 DOI: 10.1101/gad.1756509] [Citation(s) in RCA: 754] [Impact Index Per Article: 50.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Growing tumors face two major metabolic challenges-how to meet the bioenergetic and biosynthetic demands of increased cell proliferation, and how to survive environmental fluctuations in external nutrient and oxygen availability when tumor growth outpaces the delivery capabilities of the existing vasculature. Cancer cells display dramatically altered metabolic circuitry that appears to directly result from the oncogenic mutations selected during the tumorigenic process. An emerging theme in cancer biology is that many of the genes that can initiate tumorigenesis are intricately linked to metabolic regulation. In turn, it appears that a number of well-established tumor suppressors play critical roles in suppressing growth and/or proliferation when intracellular supplies of essential metabolites become reduced. In this review, we consider the potential role of tumor suppressors as metabolic regulators.
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Affiliation(s)
- Russell G Jones
- Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec, H3A 1A3, Canada.
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Kelly AP, Finlay DK, Hinton HJ, Clarke RG, Fiorini E, Radtke F, Cantrell DA. Notch-induced T cell development requires phosphoinositide-dependent kinase 1. EMBO J 2007; 26:3441-50. [PMID: 17599070 PMCID: PMC1933393 DOI: 10.1038/sj.emboj.7601761] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Accepted: 05/24/2007] [Indexed: 12/17/2022] Open
Abstract
Phosphoinositide-dependent kinase l (PDK1) phosphorylates and activates multiple AGC serine kinases, including protein kinase B (PKB), p70Ribosomal S6 kinase (S6K) and p90Ribosomal S6 kinase (RSK). PDK1 is required for thymocyte differentiation and proliferation, and herein, we explore the molecular basis for these essential functions of PDK1 in T lymphocyte development. A key finding is that PDK1 is required for the expression of key nutrient receptors in T cell progenitors: CD71 the transferrin receptor and CD98 a subunit of L-amino acid transporters. PDK1 is also essential for Notch-mediated trophic and proliferative responses in thymocytes. A PDK1 mutant PDK1 L155E, which supports activation of PKB but no other AGC kinases, can restore CD71 and CD98 expression in pre-T cells and restore thymocyte differentiation. However, PDK1 L155E is insufficient for thymocyte proliferation. The role of PDK1 in thymus development thus extends beyond its ability to regulate PKB. In addition, PDK1 phosphorylation of AGC kinases such as S6K and RSK is also necessary for thymocyte development.
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Affiliation(s)
- April P Kelly
- College of Life Science, Division of Cell Biology & Immunology, MSI/WTB complex, University of Dundee, Dundee, UK
| | - David K Finlay
- College of Life Science, Division of Cell Biology & Immunology, MSI/WTB complex, University of Dundee, Dundee, UK
| | | | - Rosie G Clarke
- College of Life Science, Division of Cell Biology & Immunology, MSI/WTB complex, University of Dundee, Dundee, UK
| | - Emma Fiorini
- The Ludwig Institute for Cancer Research, University of Lausanne, Epalinges, Switzerland
| | - Freddy Radtke
- Life Science Department, Swiss Institute for Experimental Cancer Research (ISREC), Ecole Polytechnique, Fédérale de Lausanne (EPFL), Epalinges, Switzerland
| | - Doreen A Cantrell
- College of Life Science, Division of Cell Biology & Immunology, MSI/WTB complex, University of Dundee, Dundee, UK
- Division of Cell Biology and Immunology, MSI/WTB complex, University of Dundee, Dundee, DD1 5EH, UK. Tel.: +44 1382 385047; Fax: +44 1382 385783; E-mail:
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Radu CG, Shu CJ, Shelly SM, Phelps ME, Witte ON. Positron emission tomography with computed tomography imaging of neuroinflammation in experimental autoimmune encephalomyelitis. Proc Natl Acad Sci U S A 2007; 104:1937-42. [PMID: 17261805 PMCID: PMC1783904 DOI: 10.1073/pnas.0610544104] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
2-[(18)F]Fluoro-2-deoxy-d-glucose positron emission tomography ([(18)F]FDG PET) detection of the up-regulated glycolysis associated with malignant transformation is a noninvasive imaging technique used extensively in cancer diagnosis. Although striking similarities exist in glucose transport and metabolism between tumor cells and activated immune cells, the potential use of [(18)F]FDG PET for the diagnosis and evaluation of autoimmune disorders has not been systematically investigated. Here we ask whether [(18)F]FDG PET in conjunction with computed tomography (CT) could be used to monitor a complex autoimmune disorder such as murine experimental autoimmune encephalomyelitis (EAE) and whether this approach is sensitive enough to evaluate therapeutic interventions. We found that (i) coregistration of metabolic (i.e., microPET) and high-resolution anatomical (i.e., CT) images allows serial quantification of glycolysis with [(18)F]FDG in various spinal column segments; (ii) [(18)F]FDG PET/CT can detect the increased glycolysis associated with paralysis-causing inflammatory infiltrates in the spinal cord; and (iii) the [(18)F]FDG measure of glycolysis in the spinal cord is sensitive to systemic immunosuppressive therapy. These results highlight the potential use of serial [(18)F]FDG PET/CT imaging to monitor neuroinflammation in EAE and suggest that similar approaches could be applied to the diagnosis and evaluation of other autoimmune and inflammatory disorders in animal models and in humans.
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Affiliation(s)
- Caius G. Radu
- Departments of *Molecular and Medical Pharmacology and
| | - Chengyi J. Shu
- Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine
| | | | - Michael E. Phelps
- Departments of *Molecular and Medical Pharmacology and
- Institute for Molecular Medicine
| | - Owen N. Witte
- Departments of *Molecular and Medical Pharmacology and
- Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine
- Institute for Molecular Medicine
- Institute for Stem Cell Biology and Medicine, and
- Howard Hughes Medical Institute, University of California, Los Angeles, CA 90095
- To whom correspondence should be addressed at:
Howard Hughes Medical Institute, University of California at Los Angeles, 675 Charles E. Young Drive South, 5-748 MRL Building, Los Angeles, CA 90095-1662. E-mail:
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14
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La P, Schnepp RW, D Petersen C, C Silva A, Hua X. Tumor suppressor menin regulates expression of insulin-like growth factor binding protein 2. Endocrinology 2004; 145:3443-50. [PMID: 15044367 PMCID: PMC2858565 DOI: 10.1210/en.2004-0124] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Multiple endocrine neoplasia type I (MEN1) is an inherited tumor syndrome characterized by development of tumors in multiple endocrine organs. The gene mutated in MEN1 patients, Men1, encodes a nuclear protein, menin. Menin interacts with several transcription factors and inhibits their activities. However, it is unclear whether menin is essential for the repression of the expression of endogenous genes. Here, using menin-null cells, we show that menin is essential for repression of the endogenous IGFBP-2, a gene that can regulate cell proliferation. Additionally, complementation of menin-null cells with wild-type menin, but not with a MEN1 disease-related point mutant, restores the function of menin in repressing IGFBP-2. Consistent with this, the promoter of IGFBP-2 is repressed by wild-type menin, but not by a MEN1-related point mutant. Menin also alters the structure of the chromatin surrounding the promoter of the IGFBP-2 gene, as demonstrated by the deoxyribonuclease I hypersensitivity assay. Furthermore, nuclear localization signals in menin are crucial for repressing the expression of IGFBP-2. Together, these results suggest that menin regulates the expression of the endogenous IGFBP-2 gene at least in part through the promoter of IGFBP-2.
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Affiliation(s)
- Ping La
- Abramson Family Cancer Research Institute, Department of Cancer Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6160, USA
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15
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Hyde R, Taylor PM, Hundal HS. Amino acid transporters: roles in amino acid sensing and signalling in animal cells. Biochem J 2003; 373:1-18. [PMID: 12879880 PMCID: PMC1223487 DOI: 10.1042/bj20030405] [Citation(s) in RCA: 261] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Amino acid availability regulates cellular physiology by modulating gene expression and signal transduction pathways. However, although the signalling intermediates between nutrient availability and altered gene expression have become increasingly well documented, how eukaryotic cells sense the presence of either a nutritionally rich or deprived medium is still uncertain. From recent studies it appears that the intracellular amino acid pool size is particularly important in regulating translational effectors, thus, regulated transport of amino acids across the plasma membrane represents a means by which the cellular response to amino acids could be controlled. Furthermore, evidence from studies with transportable amino acid analogues has demonstrated that flux through amino acid transporters may act as an initiator of nutritional signalling. This evidence, coupled with the substrate selectivity and sensitivity to nutrient availability classically associated with amino acid transporters, plus the recent discovery of transporter-associated signalling proteins, demonstrates a potential role for nutrient transporters as initiators of cellular nutrient signalling. Here, we review the evidence supporting the idea that distinct amino acid "receptors" function to detect and transmit certain nutrient stimuli in higher eukaryotes. In particular, we focus on the role that amino acid transporters may play in the sensing of amino acid levels, both directly as initiators of nutrient signalling and indirectly as regulators of external amino acid access to intracellular receptor/signalling mechanisms.
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Affiliation(s)
- Russell Hyde
- Division of Molecular Physiology, MSI/WTB Complex, University of Dundee, Scotland, UK
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16
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Nii T, Segawa H, Taketani Y, Tani Y, Ohkido M, Kishida S, Ito M, Endou H, Kanai Y, Takeda E. Molecular events involved in up-regulating human Na+-independent neutral amino acid transporter LAT1 during T-cell activation. Biochem J 2001; 358:693-704. [PMID: 11535130 PMCID: PMC1222103 DOI: 10.1042/0264-6021:3580693] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We investigated the regulation of system-L amino acid transporter (LAT1) during T-cell activation. In quiescent T-cells, L-leucine transport is mediated mainly by the system-L amino acid transport system and is increased significantly during T-cell activation by PMA and ionomycin. In quiescent T-cells, the LAT1 protein was heterocomplexed with 4F2 heavy chain (4F2hc) in the plasma membrane. During T-cell activation, the amounts of 4F2hc and LAT1 heterocomplex were significantly elevated compared with those in quiescent T-cells. In addition, by Northern-blot analysis, these increments were found to be due to elevated levels of LAT1 and 4F2hc mRNA. Transient expression of constructs comprising various LAT1 gene promoter fragments, which contained all three of the GC boxes, was sufficient for promoting luciferase expression in Jurkat T-cells, but the promoter of the LAT1 gene did not respond to PMA and ionomycin. Similar observations were observed in the human 4F2hc gene promoter. In nuclear run-on assay, the LAT1 and 4F2hc genes were actively transcribed even in quiescent T-cells, but the low levels of both transcripts were shown to be the result of a block to transcription elongation within the exon 1 intron 1 regions. These findings indicated that a removal of the block to mRNA elongation stimulates the induction of system-L amino acid transporter gene transcripts (LAT1 and 4F2hc) in activated T-cells.
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Affiliation(s)
- T Nii
- Department of Clinical Nutrition, School of Medicine, Tokushima University, Kuramoto-cho 3, Tokushima City 770-8503, Japan
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17
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Bröer S, Bröer A, Hamprecht B. Expression of the surface antigen 4F2hc affects system-L-like neutral-amino-acid-transport activity in mammalian cells. Biochem J 1997; 324 ( Pt 2):535-41. [PMID: 9182715 PMCID: PMC1218463 DOI: 10.1042/bj3240535] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Mammalian cells possess a variety of amino acid-transport systems with overlapping substrate specificity. System L is one of the major amino acid-transport systems of non-epithelial cells. By expression cloning we have recently demonstrated that the surface antigen 4F2hc (CD98) is a necessary component for expression of system-L-like amino acid-transport activity in C6-BU-1 rat glioma cells [Bröer, Bröer and Hamprecht (1995) Biochem. J. 312, 863-870]. 4F2hc mRNA was detected in CHO cells, COS cells, activated lymphocytes isolated from mouse spleen and primary cultures of astrocytes. In all these cell types, Na+-independent isoleucine transport was mediated by system L. No contribution of system y+L to isoleucine or arginine transport was detected in C6-BU-1 cells. In lymphocytes, both system-L-like amino acid-transport activity and 4F2hc mRNA levels increased after treatment with phorbol ester plus ionomycin. Antisense oligonucleotides caused modest inhibition of Na+-independent isoleucine transport in C6-BU-1 cells and primary cultures of astroglial cells, whereas arginine transport was unaffected. Overexpression of 4F2hc cDNA in CHO cells resulted in an increase in Na+-independent isoleucine transport.
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Affiliation(s)
- S Bröer
- Physiologisch-chemisches Institut der Universität, Hoppe-Seyler-Str. 4, D-72076 Tübingen, Germany
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18
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Functional analysis of the human adenosine deaminase gene thymic regulatory region and its ability to generate position-independent transgene expression. Mol Cell Biol 1992. [PMID: 1508212 DOI: 10.1128/mcb.12.9.4170] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We previously observed that human ADA gene expression, required for the intrathymic maturation of T cells, is controlled by first-intron sequences. Used as a cis activator, the intron generates copy-dependent reporter expression in transgenic thymocytes, and we here dissect its critical determinants. Of six DNase I-hypersensitive sites (HS sites) in the intron, only HS III was a transfection-active classic enhancer in T cells. The enhancer contains a critical core region, ACATGGCAGTTGGTGGTGGAGGGGAACA, that interacts with at least two factors, ADA-NF1 and ADA-NF2. Activity of the core is strongly augmented by adjacent elements contained within a 200-bp domain corresponding to the limits of HS III hypersensitivity. These core-adjacent sequences include consensus matches for recognition by the AP-1, TCF-1 alpha, mu E, and Ets transcription factor families. In contrast, considerably more extensive sequences flanking the enhancer domain were required for position-independent and copy-proportional expression in transgenic mouse thymocytes. The additionally required upstream segment encompassed the nonenhancer HS II site. The required downstream segment, composed largely of Alu-repetitive DNA, was non-DNase I hypersensitive. Transgenes that lacked either segment were subject to strong positional effects. Among these variably expressing lines, the expression level correlated with the degree of hypersensitivity at HS III. This finding suggests that formation of hypersensitivity is normally facilitated by the flanking segments. These results delineate a complex thymic regulatory region within the intron and indicate that a series of interactions is necessary for the enhancer domain to function consistently within chromatin.
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19
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Aronow BJ, Silbiger RN, Dusing MR, Stock JL, Yager KL, Potter SS, Hutton JJ, Wiginton DA. Functional analysis of the human adenosine deaminase gene thymic regulatory region and its ability to generate position-independent transgene expression. Mol Cell Biol 1992; 12:4170-85. [PMID: 1508212 PMCID: PMC360321 DOI: 10.1128/mcb.12.9.4170-4185.1992] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We previously observed that human ADA gene expression, required for the intrathymic maturation of T cells, is controlled by first-intron sequences. Used as a cis activator, the intron generates copy-dependent reporter expression in transgenic thymocytes, and we here dissect its critical determinants. Of six DNase I-hypersensitive sites (HS sites) in the intron, only HS III was a transfection-active classic enhancer in T cells. The enhancer contains a critical core region, ACATGGCAGTTGGTGGTGGAGGGGAACA, that interacts with at least two factors, ADA-NF1 and ADA-NF2. Activity of the core is strongly augmented by adjacent elements contained within a 200-bp domain corresponding to the limits of HS III hypersensitivity. These core-adjacent sequences include consensus matches for recognition by the AP-1, TCF-1 alpha, mu E, and Ets transcription factor families. In contrast, considerably more extensive sequences flanking the enhancer domain were required for position-independent and copy-proportional expression in transgenic mouse thymocytes. The additionally required upstream segment encompassed the nonenhancer HS II site. The required downstream segment, composed largely of Alu-repetitive DNA, was non-DNase I hypersensitive. Transgenes that lacked either segment were subject to strong positional effects. Among these variably expressing lines, the expression level correlated with the degree of hypersensitivity at HS III. This finding suggests that formation of hypersensitivity is normally facilitated by the flanking segments. These results delineate a complex thymic regulatory region within the intron and indicate that a series of interactions is necessary for the enhancer domain to function consistently within chromatin.
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Affiliation(s)
- B J Aronow
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati Children's Hospital, Ohio 45229
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20
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Ho IC, Leiden JM. The T alpha 2 nuclear protein binding site from the human T cell receptor alpha enhancer functions as both a T cell-specific transcriptional activator and repressor. J Exp Med 1990; 172:1443-9. [PMID: 2230652 PMCID: PMC2188681 DOI: 10.1084/jem.172.5.1443] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
T cell-specific expression of the human T cell receptor alpha (TCR-alpha) gene is regulated by the interaction of variable region promoter elements with a transcriptional enhancer that is located 4.5 kb 3' of the TCR-alpha constant region (C alpha) gene segment. The minimal TCR-alpha enhancer is composed of two nuclear protein binding sites, T alpha 1 and T alpha 2, that are both required for the T cell-specific activity of the enhancer. The T alpha 1 binding site contains a consensus cAMP response element (CRE), and binds a set of ubiquitous nuclear proteins. The T alpha 2 binding site does not contain known transcriptional enhancer motifs. However, it binds at least two nuclear protein complexes, one of which is T cell specific. We now report that although the T alpha 2 nuclear protein binding site displays transcriptional activator activity in the context of the TCR-alpha enhancer, this site alone can function as a potent, T cell-specific transcriptional repressor when positioned either upstream, or downstream of several heterologous promoter and enhancer elements. These results demonstrate that a single nuclear protein binding site can function as a T cell-specific transcriptional activator or repressor element, depending upon the context in which it is located.
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MESH Headings
- Base Sequence
- Binding Sites/physiology
- Cell Line
- Enhancer Elements, Genetic/genetics
- Enhancer Elements, Genetic/physiology
- Gene Expression/drug effects
- Gene Expression/physiology
- Genes, Regulator/genetics
- Genes, Regulator/physiology
- Humans
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology
- Molecular Sequence Data
- Nuclear Proteins/genetics
- Nuclear Proteins/metabolism
- Promoter Regions, Genetic/genetics
- Promoter Regions, Genetic/physiology
- Protein Binding
- Receptors, Antigen, T-Cell/genetics
- Receptors, Antigen, T-Cell/metabolism
- Receptors, Antigen, T-Cell/physiology
- T-Lymphocytes/physiology
- T-Lymphocytes/ultrastructure
- Transcription, Genetic/drug effects
- Transcription, Genetic/genetics
- Transcription, Genetic/physiology
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Affiliation(s)
- I C Ho
- Howard Hughes Medical Institute, University of Michigan Medical Center, Ann Arbor 48109
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21
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Identification and functional characterization of the human T-cell receptor beta gene transcriptional enhancer: common nuclear proteins interact with the transcriptional regulatory elements of the T-cell receptor alpha and beta genes. Mol Cell Biol 1990. [PMID: 2144610 DOI: 10.1128/mcb.10.10.5486] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A transcriptional enhancer has been mapped to a region 5.5 kilobases 3' of the C beta 2 gene in the human T-cell receptor (TCR) beta-chain locus. Transient transfections allowed localization of enhancer activity to a 480-base-pair HincII-XbaI restriction enzyme fragment. The TCR beta enhancer was active on both the minimal simian virus 40 promoter and a TCR beta variable gene promoter in both TCR alpha/beta + and TCR gamma/delta + T cells. It displayed significantly less activity in Epstein-Barr virus-transformed B cells and K562 chronic myelogenous leukemia cells and no activity in HeLa fibroblasts. DNA sequence analysis revealed that the enhancer contains a consensus immunoglobulin kappa E2 motif, as well as an AP-1-binding site and a cyclic AMP response element. DNase I footprint analyses using Jurkat T-cell nuclear extracts allowed the identification of five nuclear protein-binding sites, T beta 1 to T beta 5, within the enhancer element. Deletion and in vitro mutagenesis studies demonstrated that the T beta 2- and T beta 3- and T beta 4-binding sites are each required for full transcriptional enhancer activity. In contrast, deletion of the T beta 1- and T beta 5-binding sites had essentially no effect on enhancer function. Electrophoretic mobility shift assays demonstrated that TCR alpha/beta + and TCR gamma/delta + T cells expressed T beta 2-, T beta 3-, and T beta 4-binding activities. In contrast, non-T-cell lines, in which the enhancer was inactive, each lacked expression of at least one of these binding activities. TCR alpha and beta gene expression may be regulated by a common set of T-cell nuclear proteins in that the T beta 2 element binding a set of cyclic AMP response element-binding proteins that are also bound by the T alpha 1 element of the human TCR alpha enhancer and the decamer element present in a large number of human and murine TCR beta promoters. Similarly, the T beta 5 TCR beta-enhancer element and the T alpha 2 TCR alpha-enhancer element bind at least one common T-cell nuclear protein. Taken together, these results suggest that TCR beta gene expression is regulated by the interaction of multiple T cell nuclear proteins with a transcriptional enhancer element located 3' of the C beta 2 gene and that some of these proteins may be involved in the coordinate regulation of TCR alpha and beta gene expression.
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22
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Gottschalk LR, Leiden JM. Identification and functional characterization of the human T-cell receptor beta gene transcriptional enhancer: common nuclear proteins interact with the transcriptional regulatory elements of the T-cell receptor alpha and beta genes. Mol Cell Biol 1990; 10:5486-95. [PMID: 2144610 PMCID: PMC361259 DOI: 10.1128/mcb.10.10.5486-5495.1990] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
A transcriptional enhancer has been mapped to a region 5.5 kilobases 3' of the C beta 2 gene in the human T-cell receptor (TCR) beta-chain locus. Transient transfections allowed localization of enhancer activity to a 480-base-pair HincII-XbaI restriction enzyme fragment. The TCR beta enhancer was active on both the minimal simian virus 40 promoter and a TCR beta variable gene promoter in both TCR alpha/beta + and TCR gamma/delta + T cells. It displayed significantly less activity in Epstein-Barr virus-transformed B cells and K562 chronic myelogenous leukemia cells and no activity in HeLa fibroblasts. DNA sequence analysis revealed that the enhancer contains a consensus immunoglobulin kappa E2 motif, as well as an AP-1-binding site and a cyclic AMP response element. DNase I footprint analyses using Jurkat T-cell nuclear extracts allowed the identification of five nuclear protein-binding sites, T beta 1 to T beta 5, within the enhancer element. Deletion and in vitro mutagenesis studies demonstrated that the T beta 2- and T beta 3- and T beta 4-binding sites are each required for full transcriptional enhancer activity. In contrast, deletion of the T beta 1- and T beta 5-binding sites had essentially no effect on enhancer function. Electrophoretic mobility shift assays demonstrated that TCR alpha/beta + and TCR gamma/delta + T cells expressed T beta 2-, T beta 3-, and T beta 4-binding activities. In contrast, non-T-cell lines, in which the enhancer was inactive, each lacked expression of at least one of these binding activities. TCR alpha and beta gene expression may be regulated by a common set of T-cell nuclear proteins in that the T beta 2 element binding a set of cyclic AMP response element-binding proteins that are also bound by the T alpha 1 element of the human TCR alpha enhancer and the decamer element present in a large number of human and murine TCR beta promoters. Similarly, the T beta 5 TCR beta-enhancer element and the T alpha 2 TCR alpha-enhancer element bind at least one common T-cell nuclear protein. Taken together, these results suggest that TCR beta gene expression is regulated by the interaction of multiple T cell nuclear proteins with a transcriptional enhancer element located 3' of the C beta 2 gene and that some of these proteins may be involved in the coordinate regulation of TCR alpha and beta gene expression.
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Affiliation(s)
- L R Gottschalk
- Howard Hughes Medical Institute, University of Michigan Medical Center, Ann Arbor 48109-0650
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23
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The first intron of the 4F2 heavy-chain gene contains a transcriptional enhancer element that binds multiple nuclear proteins. Mol Cell Biol 1989. [PMID: 2761540 DOI: 10.1128/mcb.9.6.2588] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We utilized the human 4F2 heavy-chain (4F2HC) gene as a model system to study the regulation of inducible gene expression during normal human T-cell activation. Previous studies have demonstrated that 4F2HC gene expression is induced during normal T-cell activation and that the activity of the gene is regulated, at least in part, by the interaction of a constitutively active 5'-flanking housekeeping promoter and a phorbol ester-responsive transcriptional attenuator element located in the exon 1-intron 1 region of the gene. We now report that 4F2HC intron 1 contains a transcriptional enhancer element which is active on a number of heterologous promoters in a variety of murine and human cells. This enhancer element has been mapped to a 187-base-pair RsaI-AluI fragment from 4F2HC intron 1. DNase I footprinting and gel mobility shift analyses demonstrated that this fragment contains two nuclear protein-binding sites (NF-4FA and NF-4FB) which flank a consensus binding site for the inducible AP-1 transcription factor. Deletion analysis showed that the NF-4FA, NF-4FB, and AP-1 sequences are each necessary for full enhancer activity. Murine 4F2HC intron 1 displayed enhancer activity similar to that of its human counterpart. Comparison of the sequences of human and murine 4F2HC intron 1s demonstrated that the NF-4FA, NF-4FB, and AP-1 sequence motifs have been highly conserved during mammalian evolution.
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24
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Ho IC, Yang LH, Morle G, Leiden JM. A T-cell-specific transcriptional enhancer element 3' of C alpha in the human T-cell receptor alpha locus. Proc Natl Acad Sci U S A 1989; 86:6714-8. [PMID: 2788889 PMCID: PMC297916 DOI: 10.1073/pnas.86.17.6714] [Citation(s) in RCA: 136] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
A transcriptional enhancer element has been identified 4.5 kilobases 3' of C alpha (constant region alpha chain) in the human T-cell receptor (TCR) alpha-chain locus. This enhancer is active on both a TCR V alpha (variable region alpha chain) promoter and the minimal simian virus 40 promotor in TCR alpha/beta Jurkat and EL4 cells but is inactive on a V alpha promoter in human TCR gamma/delta PEER and Molt-13 cells, clone 13 B cells, and HeLa fibroblasts. The enhancer has been localized to a 116-base-pair BstXI/Dra I restriction enzyme fragment, which lacks immunoglobulin octamer and kappa B enhancer motifs but does contain a consensus cAMP-response element (CRE). DNase I footprint analyses demonstrated that the minimal enhancer contains two binding sites for Jurkat nuclear proteins. One of these sites corresponds to the CRE, while the other does not correspond to a known transcriptional enhancer motif. These data support a model in which TCR alpha gene transcription is regulated by a unique set of cis-acting sequences and trans-acting factors, which are differentially active in cells of the TCR alpha/beta lineage. In addition, the TCR alpha enhancer may play a role in activating oncogene expression in T-lymphoblastoid tumors that have previously been shown to display chromosomal translocations into the human TCR alpha locus.
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Affiliation(s)
- I C Ho
- Howard Hughes Medical Institute, University of Michigan Medical Center, Ann Arbor 48109
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25
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Karpinski BA, Yang LH, Cacheris P, Morle GD, Leiden JM. The first intron of the 4F2 heavy-chain gene contains a transcriptional enhancer element that binds multiple nuclear proteins. Mol Cell Biol 1989; 9:2588-97. [PMID: 2761540 PMCID: PMC362331 DOI: 10.1128/mcb.9.6.2588-2597.1989] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
We utilized the human 4F2 heavy-chain (4F2HC) gene as a model system to study the regulation of inducible gene expression during normal human T-cell activation. Previous studies have demonstrated that 4F2HC gene expression is induced during normal T-cell activation and that the activity of the gene is regulated, at least in part, by the interaction of a constitutively active 5'-flanking housekeeping promoter and a phorbol ester-responsive transcriptional attenuator element located in the exon 1-intron 1 region of the gene. We now report that 4F2HC intron 1 contains a transcriptional enhancer element which is active on a number of heterologous promoters in a variety of murine and human cells. This enhancer element has been mapped to a 187-base-pair RsaI-AluI fragment from 4F2HC intron 1. DNase I footprinting and gel mobility shift analyses demonstrated that this fragment contains two nuclear protein-binding sites (NF-4FA and NF-4FB) which flank a consensus binding site for the inducible AP-1 transcription factor. Deletion analysis showed that the NF-4FA, NF-4FB, and AP-1 sequences are each necessary for full enhancer activity. Murine 4F2HC intron 1 displayed enhancer activity similar to that of its human counterpart. Comparison of the sequences of human and murine 4F2HC intron 1s demonstrated that the NF-4FA, NF-4FB, and AP-1 sequence motifs have been highly conserved during mammalian evolution.
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Affiliation(s)
- B A Karpinski
- Howard Hughes Medical Institute, University of Michigan Medical Center, Ann Arbor 48109
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26
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Abstract
The small (40S) subunit of eukaryotic ribosomes is believed to bind initially at the capped 5'-end of messenger RNA and then migrate, stopping at the first AUG codon in a favorable context for initiating translation. The first-AUG rule is not absolute, but there are rules for breaking the rule. Some anomalous observations that seemed to contradict the scanning mechanism now appear to be artifacts. A few genuine anomalies remain unexplained.
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Affiliation(s)
- M Kozak
- Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260
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