1
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Kranjčević JK, Čonkaš J, Ozretić P. The Role of Estrogen and Estrogen Receptors in Head and Neck Tumors. Cancers (Basel) 2024; 16:1575. [PMID: 38672656 PMCID: PMC11049451 DOI: 10.3390/cancers16081575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 04/12/2024] [Accepted: 04/18/2024] [Indexed: 04/21/2024] Open
Abstract
Head and neck squamous cell carcinoma (HNSCC) is the most common histological form of head and neck tumors (HNTs), which originate from the epithelium of the lips and oral cavity, pharynx, larynx, salivary glands, nasal cavity, and sinuses. The main risk factors include consumption of tobacco in all forms and alcohol, as well as infections with high-risk human papillomaviruses or the Epstein-Barr virus. Regardless of the etiological agent, the risk of developing different types of HNTs is from two to more than six times higher in males than in females. The reason for such disparities probably lies in a combination of both biological and psychosocial factors. Therefore, it is hypothesized that exposure to female sex hormones, primarily estrogen, provides women with protection against the formation and metastasis of HNTs. In this review, we synthesized available knowledge on the role of estrogen and estrogen receptors (ERs) in the development and progression of HNTs, with special emphasis on membrane ERs, which are much less studied. We can summarize that in addition to epidemiologic studies unequivocally pointing to the protective effect of estrogen in women, an increased expression of both nuclear ERs, ERα, and ERβ, and membrane ERs, ERα36, GPER1, and NaV1.2, was present in different types of HNSCC, for which anti-estrogens could be used as an effective therapeutic approach.
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Affiliation(s)
| | | | - Petar Ozretić
- Laboratory for Hereditary Cancer, Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia (J.Č.)
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2
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Goelzer M, Goelzer J, Ferguson ML, Neu CP, Uzer G. Nuclear envelope mechanobiology: linking the nuclear structure and function. Nucleus 2021; 12:90-114. [PMID: 34455929 PMCID: PMC8432354 DOI: 10.1080/19491034.2021.1962610] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 07/26/2021] [Accepted: 07/27/2021] [Indexed: 01/10/2023] Open
Abstract
The nucleus, central to cellular activity, relies on both direct mechanical input as well as its molecular transducers to sense external stimuli and respond by regulating intra-nuclear chromatin organization that determines cell function and fate. In mesenchymal stem cells of musculoskeletal tissues, changes in nuclear structures are emerging as a key modulator of their differentiation and proliferation programs. In this review we will first introduce the structural elements of the nucleoskeleton and discuss the current literature on how nuclear structure and signaling are altered in relation to environmental and tissue level mechanical cues. We will focus on state-of-the-art techniques to apply mechanical force and methods to measure nuclear mechanics in conjunction with DNA, RNA, and protein visualization in living cells. Ultimately, combining real-time nuclear deformations and chromatin dynamics can be a powerful tool to study mechanisms of how forces affect the dynamics of genome function.
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Affiliation(s)
- Matthew Goelzer
- Materials Science and Engineering, Boise State University, Boise, ID, US
| | | | - Matthew L. Ferguson
- Biomolecular Science, Boise State University, Boise, ID, US
- Physics, Boise State University, Boise, ID, US
| | - Corey P. Neu
- Paul M. Rady Department of Mechanical Engineering, University of Colorado, Boulder, CO, US
| | - Gunes Uzer
- Mechanical and Biomedical Engineering, Boise State University, Boise, ID, US
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3
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Auer JMT, Stoddart JJ, Christodoulou I, Lima A, Skouloudaki K, Hall HN, Vukojević V, Papadopoulos DK. Of numbers and movement - understanding transcription factor pathogenesis by advanced microscopy. Dis Model Mech 2020; 13:dmm046516. [PMID: 33433399 PMCID: PMC7790199 DOI: 10.1242/dmm.046516] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Transcription factors (TFs) are life-sustaining and, therefore, the subject of intensive research. By regulating gene expression, TFs control a plethora of developmental and physiological processes, and their abnormal function commonly leads to various developmental defects and diseases in humans. Normal TF function often depends on gene dosage, which can be altered by copy-number variation or loss-of-function mutations. This explains why TF haploinsufficiency (HI) can lead to disease. Since aberrant TF numbers frequently result in pathogenic abnormalities of gene expression, quantitative analyses of TFs are a priority in the field. In vitro single-molecule methodologies have significantly aided the identification of links between TF gene dosage and transcriptional outcomes. Additionally, advances in quantitative microscopy have contributed mechanistic insights into normal and aberrant TF function. However, to understand TF biology, TF-chromatin interactions must be characterised in vivo, in a tissue-specific manner and in the context of both normal and altered TF numbers. Here, we summarise the advanced microscopy methodologies most frequently used to link TF abundance to function and dissect the molecular mechanisms underlying TF HIs. Increased application of advanced single-molecule and super-resolution microscopy modalities will improve our understanding of how TF HIs drive disease.
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Affiliation(s)
- Julia M T Auer
- MRC Human Genetics Unit, University of Edinburgh, Edinburgh EH4 1XU, UK
| | - Jack J Stoddart
- MRC Human Genetics Unit, University of Edinburgh, Edinburgh EH4 1XU, UK
| | | | - Ana Lima
- MRC Human Genetics Unit, University of Edinburgh, Edinburgh EH4 1XU, UK
| | | | - Hildegard N Hall
- MRC Human Genetics Unit, University of Edinburgh, Edinburgh EH4 1XU, UK
| | - Vladana Vukojević
- Center for Molecular Medicine (CMM), Department of Clinical Neuroscience, Karolinska Institutet, 17176 Stockholm, Sweden
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4
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Fadel L, Rehó B, Volkó J, Bojcsuk D, Kolostyák Z, Nagy G, Müller G, Simandi Z, Hegedüs É, Szabó G, Tóth K, Nagy L, Vámosi G. Agonist binding directs dynamic competition among nuclear receptors for heterodimerization with retinoid X receptor. J Biol Chem 2020; 295:10045-10061. [PMID: 32513869 DOI: 10.1074/jbc.ra119.011614] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 06/05/2020] [Indexed: 12/16/2022] Open
Abstract
Retinoid X receptor (RXR) plays a pivotal role as a transcriptional regulator and serves as an obligatory heterodimerization partner for at least 20 other nuclear receptors (NRs). Given a potentially limiting/sequestered pool of RXR and simultaneous expression of several RXR partners, we hypothesized that NRs compete for binding to RXR and that this competition is directed by specific agonist treatment. Here, we tested this hypothesis on three NRs: peroxisome proliferator-activated receptor gamma (PPARγ), vitamin D receptor (VDR), and retinoic acid receptor alpha (RARα). The evaluation of competition relied on a nuclear translocation assay applied in a three-color imaging model system by detecting changes in heterodimerization between RXRα and one of its partners (NR1) in the presence of another competing partner (NR2). Our results indicated dynamic competition between the NRs governed by two mechanisms. First, in the absence of agonist treatment, there is a hierarchy of affinities between RXRα and its partners in the following order: RARα > PPARγ > VDR. Second, upon agonist treatment, RXRα favors the liganded partner. We conclude that recruiting RXRα by the liganded NR not only facilitates a stimulus-specific cellular response but also might impede other NR pathways involving RXRα.
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Affiliation(s)
- Lina Fadel
- Department of Biophysics and Cell Biology, Doctoral School of Molecular Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Bálint Rehó
- Department of Biophysics and Cell Biology, Doctoral School of Molecular Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Julianna Volkó
- Department of Biophysics and Cell Biology, Doctoral School of Molecular Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Dóra Bojcsuk
- Department of Biochemistry and Molecular Biology, Doctoral School of Molecular Cell and Immune Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Zsuzsanna Kolostyák
- Department of Biochemistry and Molecular Biology, Doctoral School of Molecular Cell and Immune Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Gergely Nagy
- Department of Biochemistry and Molecular Biology, Doctoral School of Molecular Cell and Immune Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Gabriele Müller
- Biophysics of Macromolecules, German Cancer Research Center, Heidelberg, Germany
| | - Zoltan Simandi
- Department of Biochemistry and Molecular Biology, Doctoral School of Molecular Cell and Immune Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Éva Hegedüs
- Department of Biophysics and Cell Biology, Doctoral School of Molecular Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Gábor Szabó
- Department of Biophysics and Cell Biology, Doctoral School of Molecular Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Katalin Tóth
- Biophysics of Macromolecules, German Cancer Research Center, Heidelberg, Germany
| | - Laszlo Nagy
- Department of Biochemistry and Molecular Biology, Doctoral School of Molecular Cell and Immune Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary .,Johns Hopkins University School of Medicine, Department of Medicine and Biological Chemistry, Institute for Fundamental Biomedical Research, Johns Hopkins All Children's Hospital, Saint Petersburg, Florida, USA
| | - György Vámosi
- Department of Biophysics and Cell Biology, Doctoral School of Molecular Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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5
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Royer CA. Characterizing proteins in their cellular environment: Examples of recent advances in quantitative fluorescence microscopy. Protein Sci 2019; 28:1210-1221. [PMID: 31012169 DOI: 10.1002/pro.3630] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2019] [Revised: 04/20/2019] [Accepted: 04/22/2019] [Indexed: 11/12/2022]
Abstract
Quantitative characterization of protein interactions, both intramolecular and intermolecular, is crucial in understanding the mechanisms and regulation of their function. In recent years, it has become possible to obtain such information on protein systems in live cells, from bacteria to mammalian cell lines. This review discusses recent advances in measuring protein folding, absolute concentration, oligomerization, diffusion, transport, and organization at super-resolution.
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Affiliation(s)
- Catherine A Royer
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, New York, 12180
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6
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Papini C, Royer CA. Scanning number and brightness yields absolute protein concentrations in live cells: a crucial parameter controlling functional bio-molecular interaction networks. Biophys Rev 2018; 10:87-96. [PMID: 29383593 DOI: 10.1007/s12551-017-0394-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 12/29/2017] [Indexed: 12/27/2022] Open
Abstract
Biological function results from properly timed bio-molecular interactions that transduce external or internal signals, resulting in any number of cellular fates, including triggering of cell-state transitions (division, differentiation, transformation, apoptosis), metabolic homeostasis and adjustment to changing physical or nutritional environments, amongst many more. These bio-molecular interactions can be modulated by chemical modifications of proteins, nucleic acids, lipids and other small molecules. They can result in bio-molecular transport from one cellular compartment to the other and often trigger specific enzyme activities involved in bio-molecular synthesis, modification or degradation. Clearly, a mechanistic understanding of any given high level biological function requires a quantitative characterization of the principal bio-molecular interactions involved and how these may change dynamically. Such information can be obtained using fluctation analysis, in particular scanning number and brightness, and used to build and test mechanistic models of the functional network to define which characteristics are the most important for its regulation.
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Affiliation(s)
- Christina Papini
- Program in Biochemistry and Biophysics, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Catherine A Royer
- Program in Biochemistry and Biophysics, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA.
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA.
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7
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Tiwari M, Oasa S, Yamamoto J, Mikuni S, Kinjo M. A Quantitative Study of Internal and External Interactions of Homodimeric Glucocorticoid Receptor Using Fluorescence Cross-Correlation Spectroscopy in a Live Cell. Sci Rep 2017; 7:4336. [PMID: 28659593 PMCID: PMC5489515 DOI: 10.1038/s41598-017-04499-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 05/18/2017] [Indexed: 01/16/2023] Open
Abstract
Glucocorticoid receptor (GRα) is a well-known ligand-dependent transcription-regulatory protein. The classic view is that unliganded GRα resides in the cytoplasm, relocates to the nucleus after ligand binding, and then associates with a specific DNA sequence, namely a glucocorticoid response element (GRE), to activate a specific gene as a homodimer. It is still a puzzle, however, whether GRα forms the homodimer in the cytoplasm or in the nucleus before DNA binding or after that. To quantify the homodimerization of GRα, we constructed the spectrally different fluorescent protein tagged hGRα and applied fluorescence cross-correlation spectroscopy. First, the dissociation constant (Kd) of mCherry2-fused hGRα or EGFP-fused hGRα was determined in vitro. Then, Kd of wild-type hGRα was found to be 3.00 μM in the nucleus, which was higher than that in vitro. Kd of a DNA-binding-deficient mutant was 3.51 μM in the nucleus. This similarity indicated that GRα homodimerization was not necessary for DNA binding but could take place on GRE by means of GRE as a scaffold. Moreover, cytoplasmic homodimerization was also observed using GRα mutated in the nuclear localization signal. These findings support the existence of a dynamic monomer pathway and regulation of GRα function both in the cytoplasm and nucleus.
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Affiliation(s)
- Manisha Tiwari
- Laboratory of Molecular Cell Dynamics, Faculty of Advanced Life Science, Hokkaido University, Sapporo, 001-0021, Japan
| | - Sho Oasa
- Laboratory of Molecular Cell Dynamics, Faculty of Advanced Life Science, Hokkaido University, Sapporo, 001-0021, Japan
| | - Johtaro Yamamoto
- Laboratory of Molecular Cell Dynamics, Faculty of Advanced Life Science, Hokkaido University, Sapporo, 001-0021, Japan
| | - Shintaro Mikuni
- Laboratory of Molecular Cell Dynamics, Faculty of Advanced Life Science, Hokkaido University, Sapporo, 001-0021, Japan
| | - Masataka Kinjo
- Laboratory of Molecular Cell Dynamics, Faculty of Advanced Life Science, Hokkaido University, Sapporo, 001-0021, Japan.
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8
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Jalaguier S, Teyssier C, Nait Achour T, Lucas A, Bonnet S, Rodriguez C, Elarouci N, Lapierre M, Cavaillès V. Complex regulation of LCoR signaling in breast cancer cells. Oncogene 2017; 36:4790-4801. [PMID: 28414308 PMCID: PMC5562849 DOI: 10.1038/onc.2017.97] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 01/18/2017] [Accepted: 02/24/2017] [Indexed: 12/15/2022]
Abstract
Ligand-dependent corepressor (LCoR) is a transcriptional repressor of ligand-activated estrogen receptors (ERs) and other transcription factors that acts both by recruiting histone deacetylases and C-terminal binding proteins. Here, we first studied LCOR gene expression in breast cancer cell lines and tissues. We detected two mRNAs variants, LCoR and LCoR2 (which encodes a truncated LCoR protein). Their expression was highly correlated and localized in discrete nuclear foci. LCoR and LCoR2 strongly repressed transcription, inhibited estrogen-induced target gene expression and decreased breast cancer cell proliferation. By mutagenesis analysis, we showed that the helix-turn-helix domain of LCoR is required for these effects. Using in vitro interaction, coimmunoprecipitation, proximity ligation assay and confocal microscopy experiments, we found that receptor-interacting protein of 140 kDa (RIP140) is a LCoR and LCoR2 partner and that this interaction requires the HTH domain of LCoR and RIP140 N- and C-terminal regions. By increasing or silencing LCoR and RIP140 expression in human breast cancer cells, we then showed that RIP140 is necessary for LCoR inhibition of gene expression and cell proliferation. Moreover, LCoR and RIP140 mRNA levels were strongly correlated in breast cancer cell lines and biopsies. In addition, RIP140 positively regulated LCoR expression in human breast cancer cells and in transgenic mouse models. Finally, their expression correlated with overall survival of patients with breast cancer. Taken together, our results provide new insights into the mechanism of action of LCoR and RIP140 and highlight their strong interplay for the control of gene expression and cell proliferation in breast cancer cells.
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Affiliation(s)
- S Jalaguier
- IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, France.,INSERM, U1194, Montpellier, France.,Université de Montpellier, Montpellier, France.,Institut régional du Cancer de Montpellier, Montpellier, France
| | - C Teyssier
- IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, France.,INSERM, U1194, Montpellier, France.,Université de Montpellier, Montpellier, France.,Institut régional du Cancer de Montpellier, Montpellier, France
| | - T Nait Achour
- IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, France.,INSERM, U1194, Montpellier, France.,Université de Montpellier, Montpellier, France.,Institut régional du Cancer de Montpellier, Montpellier, France
| | - A Lucas
- IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, France.,INSERM, U1194, Montpellier, France.,Université de Montpellier, Montpellier, France.,Institut régional du Cancer de Montpellier, Montpellier, France
| | - S Bonnet
- IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, France.,INSERM, U1194, Montpellier, France.,Université de Montpellier, Montpellier, France.,Institut régional du Cancer de Montpellier, Montpellier, France
| | - C Rodriguez
- IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, France.,INSERM, U1194, Montpellier, France.,Université de Montpellier, Montpellier, France.,Institut régional du Cancer de Montpellier, Montpellier, France
| | - N Elarouci
- Programme Cartes d'Identité des Tumeurs (CIT), Ligue Nationale Contre Le Cancer, Paris, France
| | - M Lapierre
- IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, France.,INSERM, U1194, Montpellier, France.,Université de Montpellier, Montpellier, France.,Institut régional du Cancer de Montpellier, Montpellier, France
| | - V Cavaillès
- IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, France.,INSERM, U1194, Montpellier, France.,Université de Montpellier, Montpellier, France.,Institut régional du Cancer de Montpellier, Montpellier, France
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9
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Zhao ZW, White MD, Bissiere S, Levi V, Plachta N. Quantitative imaging of mammalian transcriptional dynamics: from single cells to whole embryos. BMC Biol 2016; 14:115. [PMID: 28010727 PMCID: PMC5180410 DOI: 10.1186/s12915-016-0331-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Probing dynamic processes occurring within the cell nucleus at the quantitative level has long been a challenge in mammalian biology. Advances in bio-imaging techniques over the past decade have enabled us to directly visualize nuclear processes in situ with unprecedented spatial and temporal resolution and single-molecule sensitivity. Here, using transcription as our primary focus, we survey recent imaging studies that specifically emphasize the quantitative understanding of nuclear dynamics in both time and space. These analyses not only inform on previously hidden physical parameters and mechanistic details, but also reveal a hierarchical organizational landscape for coordinating a wide range of transcriptional processes shared by mammalian systems of varying complexity, from single cells to whole embryos.
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Affiliation(s)
- Ziqing W Zhao
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), 61 Biopolis Drive, Singapore, 138673, Singapore
| | - Melanie D White
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), 61 Biopolis Drive, Singapore, 138673, Singapore
| | - Stephanie Bissiere
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), 61 Biopolis Drive, Singapore, 138673, Singapore
| | - Valeria Levi
- Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Conicet, Buenos Aires, C1428EHA, Argentina
| | - Nicolas Plachta
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), 61 Biopolis Drive, Singapore, 138673, Singapore.
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10
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Lubec G, Korz V. Concerted Gene Expression of Hippocampal Steroid Receptors during Spatial Learning in Male Wistar Rats: A Correlation Analysis. Front Behav Neurosci 2016; 10:94. [PMID: 27242463 PMCID: PMC4868845 DOI: 10.3389/fnbeh.2016.00094] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 04/29/2016] [Indexed: 11/29/2022] Open
Abstract
Adrenal and gonadal steroid receptor activities are significantly involved and interact in the regulation of learning, memory and stress. Thus, a coordinated expression of steroid receptor genes during a learning task can be expected. Although coexpression of steroid receptors in response to behavioral tasks has been reported the correlative connection is unclear. According to the inverted U-shape model of the impact of stress upon learning and memory we hypothesized that glucocorticoid (GR) receptor expression should be correlated to corticosterone levels in a linear or higher order manner. Other cognition modulating steroid receptors like estrogen receptors (ER) should be correlated to GR receptors in a quadratic manner, which describes a parabola and thus a U-shaped connection. Therefore, we performed a correlational meta-analyis of data of a previous study (Meyer and Korz, 2013a) of steroid receptor gene expressions during spatial learning, which provides a sufficient data basis in order to perform such correlational connections. In that study male rats of different ages were trained in a spatial holeboard or remained untrained and the hippocampal gene expression of different steroid receptors as well as serum corticosterone levels were measured. Expressions of mineralocorticoid (MR) and GR receptors were positively and linearly correlated with blood serum corticosterone levels in spatially trained but not in untrained animals. Training induced a cubic (best fit) relationship between mRNA levels of estrogen receptor α (ERα) and androgen receptor (AR) with MR mRNA. GR gene expression was linearly correlated with MR expression under both conditions. ERα m RNA levels were negatively and linearily and MR and GR gene expressions were cubicely correlated with reference memory errors (RME). Due to only three age classes correlations with age could not be performed. The findings support the U-shape theory of steroid receptor interaction, however the cubic fit suggest a more complex situation, which mechanisms may be revealed in further studies.
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Affiliation(s)
- Gert Lubec
- Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna Vienna, Austria
| | - Volker Korz
- Department of Pediatrics, Medical University of Vienna Vienna, Austria
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11
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Determination of the Dissociation Constant of the NFκB p50/p65 Heterodimer in Living Cells Using Fluorescence Cross-Correlation Spectroscopy. Methods Mol Biol 2015; 1228:173-86. [DOI: 10.1007/978-1-4939-1680-1_14] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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12
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Sase S, Meyer K, Lubec G, Korz V. Different expression of membrane-bound and cytosolic hippocampal steroid receptor complexes during spatial training in young male rats. Eur Neuropsychopharmacol 2014; 24:1819-27. [PMID: 25258178 DOI: 10.1016/j.euroneuro.2014.09.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 07/31/2014] [Accepted: 09/03/2014] [Indexed: 10/24/2022]
Abstract
Brain steroid receptors are involved in mediating stress responses and cognitive processes throughfast non-genomic signaling of membrane-bound receptors or through the slower genomic actions of cytosolic receptors. Although the contribution of these different pathways in the formation and maintenance of memories has been widely discussed, little is known about the regulation of membrane versus cytosolic receptors during a learning task. Besides the relatively well studied corticosterone-binding glucocorticoid (GR) and mineralocorticoid (MR) receptors, sex steroid hormone receptors, such as the androgen and estrogen (ERα and ERβ) receptors, have also been shown to be involved in the regulation of stress and cognition. Moreover, the latter receptors are known to be functional in both sexes. Therefore, we studied the expression of hippocampal receptors in both cellular fractions during spatial learning in male rats. Membrane and cytosolic GR were shown to be downregulated after memory acquisition and unaffected after consolidation, whereas membrane MR was upregulated after both learning phases and unaffected in the cytosol. Cytosolic ERα was downregulated after both phases and unaffected in the membrane. The remaining receptors were not regulated. The data suggest a specific role of MR and ERα during training as fast and slow mediators, respectively.
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Affiliation(s)
- Sunetra Sase
- University of Vienna, Department of Pediatrics, Vienna, Austria
| | - Katrin Meyer
- Leibniz Institute for Neurobiology, Magdeburg, Germany; University of Magdeburg, Institute of Biology, Leipziger Str. 44, 39120 Magdeburg, Germany
| | - Gert Lubec
- University of Vienna, Department of Pediatrics, Vienna, Austria
| | - Volker Korz
- University of Magdeburg, Institute of Biology, Leipziger Str. 44, 39120 Magdeburg, Germany; Center for Behavioral Brain Sciences, Magdeburg, Germany.
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13
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Recent applications of fluorescence correlation spectroscopy in live systems. FEBS Lett 2014; 588:3571-84. [PMID: 24726724 DOI: 10.1016/j.febslet.2014.03.056] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2014] [Revised: 03/29/2014] [Accepted: 03/31/2014] [Indexed: 11/20/2022]
Abstract
Fluorescence correlation spectroscopy (FCS) is a widely used technique in biophysics and has helped address many questions in the life sciences. It provides important advantages compared to other fluorescence and biophysical methods. Its single molecule sensitivity allows measuring proteins within biological samples at physiological concentrations without the need of overexpression. It provides quantitative data on concentrations, diffusion coefficients, molecular transport and interactions even in live organisms. And its reliance on simple fluorescence intensity and its fluctuations makes it widely applicable. In this review we focus on applications of FCS in live samples, with an emphasis on work in the last 5 years, in the hope to provide an overview of the present capabilities of FCS to address biologically relevant questions.
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14
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Hink MA. Quantifying intracellular dynamics using fluorescence fluctuation spectroscopy. PROTOPLASMA 2014; 251:307-316. [PMID: 24420265 DOI: 10.1007/s00709-013-0602-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 12/12/2013] [Indexed: 06/03/2023]
Abstract
Originally developed for the field of physical chemistry, fluorescence fluctuation spectroscopy (FFS) has evolved to a family of methods to quantify concentrations, diffusion rates and interactions of fluorescently labelled molecules. The possibility to measure at the nanomolar concentration level and to combine these techniques with microscopy allow to study biological processes with high sensitivity in the living cell. In this review, the basic principles, challenges and recent developments of the most common FFS methods are being discussed and illustrated by intracellular applications.
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Affiliation(s)
- Mark A Hink
- Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy (LCAM), Swammerdam Institute for Life Sciences (SILS), University of Amsterdam, Sciencepark 904, 1098 XH, Amsterdam, The Netherlands,
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15
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Moutin E, Compan V, Raynaud F, Clerté C, Bouquier N, Labesse G, Ferguson ML, Fagni L, Royer CA, Perroy J. Stoichiometry of scaffold complexes in living neurons - DLC2 as a dimerization engine for GKAP. J Cell Sci 2014; 127:3451-62. [DOI: 10.1242/jcs.145748] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Quantitative spatio-temporal characterization of protein interactions in living cells remains a major challenge facing modern biology. We have investigated in living neurons the spatial dependence of the stoichiometry of interactions between two core proteins of the NMDA receptor-associated scaffolding complex, GKAP and DLC2, using a novel variation of Fluorescence Fluctuation Microscopy called two-photon scanning Number and Brightness (sN&B). We found that dimerization of DLC2 was required for its interaction with GKAP, which in turn potentiated GKAP self-association. In dendritic shaft, the DLC2-GKAP hetero-oligomeric complexes were composed mainly of 2 DLC2 and 2 GKAP monomers, while in spines, the hetero-complexes were much larger, with an average of ∼16 DLC2 and ∼13 GKAP. Disruption of the GKAP-DLC2 interaction strongly destabilized the oligomers, decreasing the spine-preferential localization of GKAP and inhibiting NMDA receptor activity. Hence, DLC2 serves a hub function in the control of glutamatergic transmission via ordering of GKAP-containing complexes in dendritic spines. Beyond illuminating the role of DLC2–GKAP interactions in glutamergic signalling, these data underscore the power of the sN&B approach for quantitative spatio-temporal imaging of other important protein complexes.
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16
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Abstract
Fluorescence cross-correlation spectroscopy (FCCS) is a single-molecule sensitive technique to quantitatively study interactions among fluorescently tagged biomolecules. Besides the initial implementation as dual-color FCCS (DC-FCCS), FCCS has several powerful derivatives, including single-wavelength FCCS (SW-FCCS), two-photon FCCS (TP-FCCS), and pulsed interleaved excitation FCCS (PIE-FCCS). However, to apply FCCS successfully, one needs to be familiar with procedures ranging from fluorescent labeling, instrumentation setup and alignment, sample preparation, and data analysis. Here, we describe the procedures to apply FCCS in various biological samples ranging from live cells to in vivo measurements, with the focus on DC-FCCS and SW-FCCS.
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17
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Hendrix J, Lamb DC. Implementation and application of pulsed interleaved excitation for dual-color FCS and RICS. Methods Mol Biol 2014; 1076:653-682. [PMID: 24108649 DOI: 10.1007/978-1-62703-649-8_30] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Pulsed interleaved excitation (PIE) employs pulsed laser sources that are interleaved such that differentially colored fluorophores can be measured or imaged quasi-simultaneously in the absence of spectral crosstalk. PIE improves the robustness and reduces data analysis complexity of many fluorescence techniques, such as fluorescence cross-correlation spectroscopy (FCCS) and raster image cross-correlation spectroscopy (ccRICS), two methods used for quantitative investigation of molecular interactions in vitro and in living cells. However, as PIE is most often used for fluorescence fluctuation spectroscopy and burst analysis experiments and utilizes time-correlated single-photon counting detection and advanced optoelectronics, it has remained a technique that is mostly used by specialized single-molecule research groups. This protocols chapter provides an accessible overview of PIE for anyone considering implementing the method on a homebuilt or commercial microscope. We give details on the instrumentation, data collection and analysis software, on how to properly set up and align a PIE microscope, and finally, on how to perform proper dual-color FCS and RICS experiments.
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Affiliation(s)
- Jelle Hendrix
- Physical Chemistry, Department of Chemistry, Munich Center for Integrated Protein Science (CiPSM) and Center for Nanoscience (CeNS), Ludwig-Maximilian-Universität München, Munich, Germany
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18
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Meyer K, Korz V. Estrogen receptor α functions in the regulation of motivation and spatial cognition in young male rats. PLoS One 2013; 8:e79303. [PMID: 24236119 PMCID: PMC3827345 DOI: 10.1371/journal.pone.0079303] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Accepted: 09/22/2013] [Indexed: 11/24/2022] Open
Abstract
Estrogenic functions in regulating behavioral states such as motivation, mood, anxiety, and cognition are relatively well documented in female humans and animals. In males, however, although the entire enzymatic machinery for producing estradiol and the corresponding receptors are present, estrogenic functions have been largely neglected. Therefore, and as a follow-up study to previous research, we sub-chronically applied a specific estrogen receptor α (ERα) antagonist in young male rats before and during a spatial learning task (holeboard). The male rats showed a dose-dependent increase in motivational, but not cognitive, behavior. The expression of hippocampal steroid receptor genes, such as glucocorticoid (GR), mineralocorticoid (MR), androgen (AR), and the estrogen receptor ERα but not ERβ was dose-dependently reduced. The expression of the aromatase but not the brain-derived neurotrophic factor (BDNF) encoding gene was also suppressed. Reduced gene expression and increased behavioral performance converged at an antagonist concentration of 7.4 µmol. The hippocampal and blood serum hormone levels (corticosterone, testosterone, and 17β-estradiol) did not differ between the experimental groups and controls. We conclude that steroid receptors (and BDNF) act in a concerted, network-like manner to affect behavior and mutual gene expression. Therefore, the isolated view on single receptor types is probably insufficient to explain steroid effects on behavior. The steroid network may keep motivation in homeostasis by supporting and constraining the behavioral expression of motivation.
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Affiliation(s)
- Katrin Meyer
- Leibniz Institute for Neurobiology, Magdeburg, Germany
- Institute for Biology, Otto-von-Guericke University, Magdeburg, Germany
| | - Volker Korz
- Institute for Biology, Otto-von-Guericke University, Magdeburg, Germany
- Center for Behavioral Neuroscience, Magdeburg, Germany
- * E-mail:
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19
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Herrick-Davis K, Grinde E, Cowan A, Mazurkiewicz JE. Fluorescence correlation spectroscopy analysis of serotonin, adrenergic, muscarinic, and dopamine receptor dimerization: the oligomer number puzzle. Mol Pharmacol 2013; 84:630-42. [PMID: 23907214 DOI: 10.1124/mol.113.087072] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The issue of G protein-coupled receptor (GPCR) oligomer status has not been resolved. Although many studies have provided evidence in favor of receptor-receptor interactions, there is no consensus as to the exact oligomer size of class A GPCRs. Previous studies have reported monomers, dimers, tetramers, and higher-order oligomers. In the present study, this issue was examined using fluorescence correlation spectroscopy (FCS) with photon counting histogram (PCH) analysis, a sensitive method for monitoring diffusion and oligomer size of plasma membrane proteins. Six different class A GPCRs were selected from the serotonin (5-HT2A), adrenergic (α1b-AR and β2-AR), muscarinic (M1 and M2), and dopamine (D1) receptor families. Each GPCR was C-terminally labeled with green fluorescent protein (GFP) or yellow fluorescent protein (YFP) and expressed in human embryonic kidney 293 cells. FCS provided plasma membrane diffusion coefficients on the order of 7.5 × 10(-9) cm(2)/s. PCH molecular brightness analysis was used to determine the GPCR oligomer size. Known monomeric (CD-86) and dimeric (CD-28) receptors with GFP and YFP tags were used as controls to determine the molecular brightness of monomers and dimers. PCH analysis of fluorescence-tagged GPCRs revealed molecular brightness values that were twice the monomeric controls and similar to the dimeric controls. Reduced χ(2) analyses of the PCH data best fit a model for a homogeneous population of homodimers, without tetramers or higher-order oligomers. The homodimer configuration was unaltered by agonist treatment and was stable over a 10-fold range of receptor expression level. The results of this study demonstrate that biogenic amine receptors freely diffusing within the plasma membrane are predominantly homodimers.
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Affiliation(s)
- Katharine Herrick-Davis
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York (K.H.-D., E.G., J.E.M.); and Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut (A.C.)
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20
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Docquier A, Garcia A, Savatier J, Boulahtouf A, Bonnet S, Bellet V, Busson M, Margeat E, Jalaguier S, Royer C, Balaguer P, Cavaillès V. Negative regulation of estrogen signaling by ERβ and RIP140 in ovarian cancer cells. Mol Endocrinol 2013; 27:1429-41. [PMID: 23885094 DOI: 10.1210/me.2012-1351] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
In hormone-dependent tissues such as breast and ovary, tumorigenesis is associated with an altered expression ratio between the two estrogen receptor (ER) subtypes. In this study, we investigated the effects of ERβ ectopic expression on 17β-estradiol (E2)-induced transactivation and cell proliferation in ERα-positive BG1 ovarian cancer cells. As expected, ERβ expression strongly decreased the mitogenic effect of E2, significantly reduced E2-dependent transcriptional responses (both on a stably integrated estrogen response element [ERE] reporter gene and on E2-induced mRNAs), and strongly enhanced the formation of ER heterodimers as evidenced by chromatin immunoprecipitation analysis. Inhibition by the ERα-selective ligand propyl pyrazole triol was less marked than with the pan-agonist (E2) or the ERβ-selective (8β-vinyl-estradiol) ligands, indicating that ERβ activation reinforced the inhibitory effects of ERβ. Interestingly, in E2-stimulated BG1 cells, ERβ was more efficient than ERα to regulate the expression of receptor-interacting protein 140 (RIP140), a major ERα transcriptional corepressor. In addition, we found that the RIP140 protein interacted better with ERβ than with ERα (both in vitro and in intact cells by fluorescence cross-correlation spectroscopy). Moreover, RIP140 recruitment on the stably integrated reporter ERE was increased upon ERβ overexpression, and ERβ activity was more sensitive to repression by RIP140. Finally, small interfering RNA-mediated knockdown of RIP140 expression abolished the repressive effect exerted by activated ERβ on the regulation of ERE-controlled transcription by estrogens. Altogether, these data demonstrate the inhibitory effects of ERβ on estrogen signaling in ovarian cancer cells and the key role that RIP140 plays in this phenomenon.
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Affiliation(s)
- Aurélie Docquier
- Institut de Recherche en Cancérologie de Montpellier, INSERM, U896, Montpellier F-34298, France
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21
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Tiwari M, Mikuni S, Muto H, Kinjo M. Determination of dissociation constant of the NFκB p50/p65 heterodimer using fluorescence cross-correlation spectroscopy in the living cell. Biochem Biophys Res Commun 2013; 436:430-5. [PMID: 23751347 DOI: 10.1016/j.bbrc.2013.05.121] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Accepted: 05/29/2013] [Indexed: 12/29/2022]
Abstract
Two-laser-beam fluorescence cross-correlation spectroscopy (FCCS) is promising technique that provides quantitative information about the interactions of biomolecules. The p50/p65 heterodimer is the most abundant and well understood of the NFκB dimers in most cells. However, the quantitative value of affinity, namely the K(d), for the heterodimer in living cells is not known yet. To quantify the heterodimerization of the IPT domain of p50/p65 in the living cell, we used two-laser-beam FCCS. The K(d) values of mCherry2- and EGFP-fused p50 and p65 were determined to be 0.46 μM in the cytoplasm and 1.06 μM in the nucleus of the living cell. These results suggest the different binding affinities of the p50/p65 heterodimer in the cytoplasm and nucleus of the living cell and different complex formation in each region.
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Affiliation(s)
- Manisha Tiwari
- Laboratory of Molecular Cell Dynamics, Faculty of Advanced Life Science, Hokkaido University, Sapporo 001-0021, Japan
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22
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Meyer K, Korz V. Age dependent differences in the regulation of hippocampal steroid hormones and receptor genes: relations to motivation and cognition in male rats. Horm Behav 2013; 63:376-84. [PMID: 23238103 DOI: 10.1016/j.yhbeh.2012.12.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Revised: 11/28/2012] [Accepted: 12/03/2012] [Indexed: 11/16/2022]
Abstract
Estrogen and estrogenic functions are age-dependently involved in the modulation of learning, memory and mood in female humans and animals. However, the investigation of estrogenic effects in males has been largely neglected. Therefore, we investigated the hippocampal gene expression of estrogen receptors α and β (ERα, β) in 8-week-old, 12-week-old and 24-week-old male rats. To control for possible interactions between the expression of the estrogen receptor genes and other learning-related steroid receptors, androgen receptors (AR), corticosterone-binding glucocorticoid receptors (GR) and mineralocorticoid receptors (MR) were also measured. Furthermore, the concentrations of the ligands 17β-estradiol, testosterone and corticosterone were measured. The spatial training was conducted in a hole-board. The 8-week-old rats exhibited higher levels of general activity and exploration during the training and performed best with respect to spatial learning and memory, whereas no difference was found between the 12-week-old and 24-week-old rats. The trained 8-week-old rats exhibited increased gene expression of ERα compared with the untrained rats in this age group as well as the trained 12-week-old and 24-week-old rats. The concentrations of estradiol and testosterone, however, were generally higher in the 24-week-old rats than in the 8-week-old and 12-week-old rats. The ERα mRNA concentrations correlated positively with behavior that indicate general learning motivation. These results suggest a specific role of ERα in the age-related differences in motivation and subsequent success in the task. Thus, estrogen and estrogenic functions may play a more prominent role in young male behavior and development than has been previously assumed.
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Affiliation(s)
- K Meyer
- Leibniz Institute for Neurobiology, Brenneckestr. 6, 39118 Magdeburg, Germany.
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23
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Jameson DM, James NG, Albanesi JP. Fluorescence fluctuation spectroscopy approaches to the study of receptors in live cells. Methods Enzymol 2013; 519:87-113. [PMID: 23280108 DOI: 10.1016/b978-0-12-405539-1.00003-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Communication between cells and their environment, including other cells, is often mediated by cell surface receptors. Fluorescence methodologies are among the most important techniques used to study receptors and their interactions, and in the past decade, fluorescence fluctuation spectroscopy (FFS) approaches have been increasingly utilized. In this overview, we illustrate how diverse FFS approaches have been used to elucidate important aspects of receptor systems, including interactions of receptors with their ligands and receptor oligomerization and clustering. We also describe the most popular methods used to introduce fluorescent moieties into the biological systems. Finally, specific attention will be given to cell maintenance and transfection strategies especially as related to microscopy studies.
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Affiliation(s)
- David M Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA.
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24
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Weidemann T, Schwille P. Dual-color fluorescence cross-correlation spectroscopy with continuous laser excitation in a confocal setup. Methods Enzymol 2013; 518:43-70. [PMID: 23276535 DOI: 10.1016/b978-0-12-388422-0.00003-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Fluorescence correlation spectroscopy evaluates local signal fluctuations arising from stochastic movements of fluorescent particles in solution. The measured fluctuating signal is correlated in time and analyzed with appropriate model functions containing the parameters that describe the underlying molecular behavior. The dual-color extension, fluorescence cross-correlation spectroscopy (FCCS) allows for a comparison between spectrally well-separated channels to extract codiffusion events that reflect interactions between differently labeled molecules. In addition to solution measurements, FCCS can be applied with subcellular resolution and is therefore a very promising approach for a quantitative biochemical assessment of molecular networks in living cells. To derive thermodynamic and kinetic reaction parameters, the influence of a number of other factors like background noise, illumination intensity profiles, photophysical processes, and cross talk between the channels have to be treated. Here, we provide a roadmap to derive binding reaction data with dual-color FCCS using continuous wave laser excitation, as it is now accessible with many state-of-the-art confocal microscopes.
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Affiliation(s)
- Thomas Weidemann
- Biophysics/BIOTEC, Technische Universität Dresden, Dresden, Germany.
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25
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26
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Herrick-Davis K, Grinde E, Lindsley T, Cowan A, Mazurkiewicz JE. Oligomer size of the serotonin 5-hydroxytryptamine 2C (5-HT2C) receptor revealed by fluorescence correlation spectroscopy with photon counting histogram analysis: evidence for homodimers without monomers or tetramers. J Biol Chem 2012; 287:23604-14. [PMID: 22593582 PMCID: PMC3390635 DOI: 10.1074/jbc.m112.350249] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 04/05/2012] [Indexed: 11/06/2022] Open
Abstract
Fluorescence correlation spectroscopy (FCS) and photon counting histogram (PCH) are techniques with single molecule sensitivity that are well suited for examining the biophysical properties of protein complexes in living cells. In the present study, FCS and PCH were applied to determine the diffusion coefficient and oligomeric size of G-protein-coupled receptors. FCS was used to record fluctuations in fluorescence intensity arising from fluorescence-tagged 5-hydroxytryptamine 2C (5-HT(2C)) receptors diffusing within the plasma membrane of HEK293 cells and rat hippocampal neurons. Autocorrelation analysis yielded diffusion coefficients ranging from 0.8 to 1.2 μm(2)/s for fluorescence-tagged receptors. Because the molecular brightness of a fluorescent protein is directly proportional to the number of fluorescent proteins traveling together within a protein complex, it can be used to determine the oligomeric size of the protein complex. FCS and PCH analysis of fluorescence-tagged 5-HT(2C) receptors provided molecular brightness values that were twice that of GFP and YFP monomeric controls, similar to a dimeric GFP control, and unaltered by 5-HT. Bimolecular fluorescence complementation of the N- and C-terminal halves of YFP attached to 5-HT(2C) receptors was observed in endoplasmic reticulum/Golgi and plasma membranes with a brightness equal to monomeric YFP. When GFP-tagged 5-HT(2C) receptors were co-expressed with a large excess of untagged, non-fluorescent 5-HT(2C) receptors, the molecular brightness was reduced by half. PCH analysis of the FCS data were best described by a one-component dimer model without monomers or tetramers. Therefore, it is concluded that 5-HT(2C) receptors freely diffusing within the plasma membrane are dimeric.
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MESH Headings
- Animals
- Cell Membrane/drug effects
- Cell Membrane/metabolism
- Cells, Cultured
- Diffusion/drug effects
- Endoplasmic Reticulum/metabolism
- Fluorescence
- Golgi Apparatus/metabolism
- Green Fluorescent Proteins/chemistry
- Green Fluorescent Proteins/genetics
- Green Fluorescent Proteins/metabolism
- HEK293 Cells
- Hippocampus/cytology
- Humans
- Luminescent Proteins/chemistry
- Luminescent Proteins/genetics
- Luminescent Proteins/metabolism
- Microscopy, Confocal
- Mutation
- Neurons/cytology
- Neurons/drug effects
- Neurons/metabolism
- Protein Multimerization
- Protein Transport/drug effects
- Rats
- Rats, Sprague-Dawley
- Receptor, Serotonin, 5-HT2C/chemistry
- Receptor, Serotonin, 5-HT2C/genetics
- Receptor, Serotonin, 5-HT2C/metabolism
- Serotonin/pharmacology
- Spectrometry, Fluorescence/methods
- Transfection
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Affiliation(s)
- Katharine Herrick-Davis
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York 12208, USA.
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27
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Navaratnarajah P, Steele BL, Redinbo MR, Thompson NL. Rifampicin-independent interactions between the pregnane X receptor ligand binding domain and peptide fragments of coactivator and corepressor proteins. Biochemistry 2011; 51:19-31. [PMID: 22185585 DOI: 10.1021/bi2011674] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The pregnane X receptor (PXR), a member of the nuclear receptor superfamily, regulates the expression of drug-metabolizing enzymes in a ligand-dependent manner. The conventional view of nuclear receptor action is that ligand binding enhances the receptor's affinity for coactivator proteins, while decreasing its affinity for corepressors. To date, however, no known rigorous biophysical studies have been conducted to investigate the interaction among PXR, its coregulators, and ligands. In this work, steady-state total internal reflection fluorescence microscopy (TIRFM) and total internal reflection with fluorescence recovery after photobleaching were used to measure the thermodynamics and kinetics of the interaction between the PXR ligand binding domain and a peptide fragment of the steroid receptor coactivator-1 (SRC-1) in the presence and absence of the established PXR agonist, rifampicin. Equilibrium dissociation and dissociation rate constants of ~5 μM and ~2 s(-1), respectively, were obtained in the presence and absence of rifampicin, indicating that the ligand does not enhance the affinity of the PXR and SRC-1 fragments. Additionally, TIRFM was used to examine the interaction between PXR and a peptide fragment of the corepressor protein, the silencing mediator for retinoid and thyroid receptors (SMRT). An equilibrium dissociation constant of ~70 μM was obtained for SMRT in the presence and absence of rifampicin. These results strongly suggest that the mechanism of ligand-dependent activation in PXR differs significantly from that seen in many other nuclear receptors.
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Affiliation(s)
- Punya Navaratnarajah
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599-7260, United States
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28
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Absolute quantification of gene expression in individual bacterial cells using two-photon fluctuation microscopy. Anal Biochem 2011; 419:250-9. [PMID: 21907700 DOI: 10.1016/j.ab.2011.08.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 08/08/2011] [Accepted: 08/10/2011] [Indexed: 11/22/2022]
Abstract
Quantification of promoter activity or protein expression in gene regulatory networks is generally achieved via measurement of fluorescent protein (FP) intensity, which is related to the true FP concentration by an unknown scaling factor, thereby limiting analysis and interpretation. Here, using approaches originally developed for eukaryotic cells, we show that two-photon (2p) fluorescence fluctuation microscopy, specifically scanning number and brightness (sN&B) analysis, can be applied to determine the absolute concentrations of diffusing FPs in live bacterial cells. First, we demonstrate the validity of the approach, despite the small size of the bacteria, using the central pixels and spatial averaging. We established the lower detection limit at or below 75 nM (~3 molecules of FP/vol(ex)) and the upper detection limit at approximately 10 μM, which can be extended using intensity measurements. We found that the uncertainty inherent in our measurements (<5%) was smaller than the high cell-cell variations observed for stochastic leakage from FP fusions of the lac promoter in the repressed state or the 10 to 25% variation observed on induction. This demonstrates that a reliable and absolute measure of transcriptional noise can be made using our approach, which should make it particularly appropriate for the investigation of stochasticity in gene expression networks.
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29
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Padilla-Parra S, Audugé N, Coppey-Moisan M, Tramier M. Dual-color fluorescence lifetime correlation spectroscopy to quantify protein-protein interactions in live cell. Microsc Res Tech 2011; 74:788-93. [DOI: 10.1002/jemt.21015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Accepted: 03/15/2011] [Indexed: 12/12/2022]
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30
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Fluorescence Correlation and Cross-Correlation Spectroscopy Using Fluorescent Proteins for Measurements of Biomolecular Processes in Living Organisms. FLUORESCENT PROTEINS II 2011. [DOI: 10.1007/4243_2011_16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
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