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Gurevich VV. Arrestins: A Small Family of Multi-Functional Proteins. Int J Mol Sci 2024; 25:6284. [PMID: 38892473 PMCID: PMC11173308 DOI: 10.3390/ijms25116284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2024] [Revised: 05/24/2024] [Accepted: 05/31/2024] [Indexed: 06/21/2024] Open
Abstract
The first member of the arrestin family, visual arrestin-1, was discovered in the late 1970s. Later, the other three mammalian subtypes were identified and cloned. The first described function was regulation of G protein-coupled receptor (GPCR) signaling: arrestins bind active phosphorylated GPCRs, blocking their coupling to G proteins. It was later discovered that receptor-bound and free arrestins interact with numerous proteins, regulating GPCR trafficking and various signaling pathways, including those that determine cell fate. Arrestins have no enzymatic activity; they function by organizing multi-protein complexes and localizing their interaction partners to particular cellular compartments. Today we understand the molecular mechanism of arrestin interactions with GPCRs better than the mechanisms underlying other functions. However, even limited knowledge enabled the construction of signaling-biased arrestin mutants and extraction of biologically active monofunctional peptides from these multifunctional proteins. Manipulation of cellular signaling with arrestin-based tools has research and likely therapeutic potential: re-engineered proteins and their parts can produce effects that conventional small-molecule drugs cannot.
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A Modeling and Analysis Study Reveals That CaMKII in Synaptic Plasticity Is a Dominant Affecter in CaM Systems in a T286 Phosphorylation-Dependent Manner. Molecules 2022; 27:molecules27185974. [PMID: 36144710 PMCID: PMC9501549 DOI: 10.3390/molecules27185974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/18/2022] [Accepted: 08/25/2022] [Indexed: 11/17/2022] Open
Abstract
NMDAR-dependent synaptic plasticity in the hippocampus consists of two opposing forces: long-term potentiation (LTP), which strengthens synapses and long-term depression (LTD), which weakens synapses. LTP and LTD are associated with memory formation and loss, respectively. Synaptic plasticity is controlled at a molecular level by Ca2+-mediated protein signaling. Here, Ca2+ binds the protein, calmodulin (CaM), which modulates synaptic plasticity in both directions. This is because Ca2+-bound CaM activates both LTD-and LTP-inducing proteins. Understanding how CaM responds to Ca2+ signaling and how this translates into synaptic plasticity is therefore important to understanding synaptic plasticity induction. In this paper, CaM activation by Ca2+ and calmodulin binding to downstream proteins was mathematically modeled using differential equations. Simulations were monitored with and without theoretical knockouts and, global sensitivity analyses were performed to determine how Ca2+/CaM signaling occurred at various Ca2+ signals when CaM levels were limiting. At elevated stimulations, the total CaM pool rapidly bound to its protein binding targets which regulate both LTP and LTD. This was followed by CaM becoming redistributed from low-affinity to high-affinity binding targets. Specifically, CaM was redistributed away from LTD-inducing proteins to bind the high-affinity LTP-inducing protein, calmodulin-dependent kinase II (CaMKII). In this way, CaMKII acted as a dominant affecter and repressed activation of opposing CaM-binding protein targets. The model thereby showed a novel form of CaM signaling by which the two opposing pathways crosstalk indirectly. The model also found that CaMKII can repress cAMP production by repressing CaM-regulated proteins, which catalyze cAMP production. The model also found that at low Ca2+ stimulation levels, typical of LTD induction, CaM signaling was unstable and is therefore unlikely to alone be enough to induce synaptic depression. Overall, this paper demonstrates how limiting levels of CaM may be a fundamental aspect of Ca2+ regulated signaling which allows crosstalk among proteins without requiring directly interaction.
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Giles J, Lopez V, McConnaha E, Hayden M, Kragenbring C, Carli D, Wauson E, Tran QK. Regulation of basal autophagy by calmodulin availability. FEBS J 2022; 289:5322-5340. [PMID: 35285161 DOI: 10.1111/febs.16432] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Revised: 01/17/2022] [Accepted: 03/10/2022] [Indexed: 01/18/2023]
Abstract
Macroautophagy (hereafter autophagy) is a process that degrades cellular components to maintain homeostasis. The Ca2+ sensor calmodulin (CaM) regulates numerous cell functions but is a limiting factor due to its insufficient availability for all target proteins. However, evidence that CaM availability regulates basal autophagy is lacking. Here, we have tested this hypothesis. CaM antagonists W-7, trifluoperazine and CGS9343b cause autophagosome accumulation and inhibit basal autophagic flux in the same manner as does chloroquine. These reagents promote the activity of AMP-activated protein kinase (AMPK) but not that of the mechanistic target of rapamycin (mTOR). Competitive binding assays using CaM sensors with different Ca2+ dependencies showed that chloroquine directly binds CaM in a Ca2+ -dependent fashion. The CaM antagonists have disparate effects on cytoplasmic Ca2+ , triggering from none to robust signals, indicating that their consistent inhibition of autophagy is due to inhibition of CaM and not Ca2+ . Chelating intracellular Ca2+ reduces the effect of the CaM antagonists to accumulate LC3-II, indicating that they do so by inhibiting CaM-dependent activities at basal Ca2+ level. The CaM antagonists cause lysosomal alkalinisation. Consistently, buffering CaM with a high-affinity CaM-binding protein that binds CaM at resting Ca2+ level increases lysosomal pH. Enhanced CaM buffering using a chimeric protein that contains two high-affinity CaM-binding sites that can collectively bind CaM at a large range of Ca2+ further increases lysosomal pH and increases LC3-II accumulation and AMPK activity, but not that of mTOR. These data demonstrate that CaM availability is required for basal autophagy.
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Affiliation(s)
- Jennifer Giles
- Department of Physiology & Pharmacology, Des Moines University College of Osteopathic Medicine, IA, USA
| | - Vanessa Lopez
- Department of Physiology & Pharmacology, Des Moines University College of Osteopathic Medicine, IA, USA
| | - Elizabeth McConnaha
- Department of Physiology & Pharmacology, Des Moines University College of Osteopathic Medicine, IA, USA
| | - Matthew Hayden
- Department of Physiology & Pharmacology, Des Moines University College of Osteopathic Medicine, IA, USA
| | - Caleb Kragenbring
- Department of Physiology & Pharmacology, Des Moines University College of Osteopathic Medicine, IA, USA
| | - David Carli
- Department of Physiology & Pharmacology, Des Moines University College of Osteopathic Medicine, IA, USA
| | - Eric Wauson
- Department of Physiology & Pharmacology, Des Moines University College of Osteopathic Medicine, IA, USA
| | - Quang-Kim Tran
- Department of Physiology & Pharmacology, Des Moines University College of Osteopathic Medicine, IA, USA
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4
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Endothelial regulation of calmodulin expression and eNOS-calmodulin interaction in vascular smooth muscle. Mol Cell Biochem 2022; 477:1489-1498. [PMID: 35171400 DOI: 10.1007/s11010-022-04391-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 02/10/2022] [Indexed: 10/19/2022]
Abstract
Calmodulin (CaM) is a Ca2+ sensor protein that is required for numerous vascular smooth muscle cell (VSMC) functions. Since CaM is not expressed enough for its many target proteins, factors that modulate its expression and interactions with targets in VSMCs can have extensive effects on vascular functions. VSMCs receive many regulatory inputs from endothelial cells (ECs). However, it is unknown if ECs regulate vascular functions via controlling expression of CaM and its interactions in VSMCs. In this work, we tested the hypothesis that ECs also affect VSMC signaling via regulation of CaM expression and interactions with its target proteins in VSMCs. Using ECs and VSMCs isolated from the same vessels and grown in a co-culture system, we observed that the presence of proliferating ECs significantly upregulates total CaM expression in VSMCs. An imaging module was devised to concurrently measure free Ca2+ and CaM levels in VSMCs in co-culture with ECs. Using indo-1/AM and a CaM biosensor built from a modified CaM-binding sequence of endothelial nitric oxide synthase (eNOS), this system revealed that in response to a generic Ca2+ signal, free Ca2+-bound CaM level is enhanced ~ threefold in VSMCs in co-culture with proliferating ECs. Interestingly, VSMCs express eNOS and eNOS-CaM association in response to the same Ca2+ stimulus is also enhanced ~ threefold in VSMCs co-cultured with ECs. Mechanistically, the endothelium-dependent upregulation of CaM in VSMCs is not affected by inhibition of NO production or endothelin receptors but is prevented by inhibition of vascular endothelial growth factor receptors. Consistently, VEGF-A level is upregulated in VSMCs co-cultured with proliferating ECs. These data indicate a new role of the endothelium in regulating vascular functions via upregulating CaM and its interactions in VSMCs.
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Kaster K, Patton J, Clayton S, Wauson E, Giles J, Tran QK. A novel assay to assess the effects of estrogen on the cardiac calmodulin binding equilibrium. Life Sci 2022; 290:120247. [PMID: 34954214 PMCID: PMC8779721 DOI: 10.1016/j.lfs.2021.120247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 12/08/2021] [Accepted: 12/14/2021] [Indexed: 02/03/2023]
Abstract
AIMS The Ca2+-binding protein calmodulin (CaM) modulates numerous target proteins but is produced insufficiently to bind all of them, generating a limiting CaM equilibrium. Menopause increases cardiac morbidity; however, it is unknown if the cardiac CaM equilibrium is affected by estrogen. We devised an assay to assess the effects of ovariectomy and estrogen treatment on the cardiac CaM equilibrium. MATERIALS AND METHODS Sprague-Dawley rats received sham surgery or ovariectomy, followed by 2-week treatment with vehicle or 17β-estradiol. Ca2+-saturated left ventricular (LV) lysates were processed through CaM sepharose columns, which retained CaM-binding proteins unoccupied by endogenous CaM. Eluants therefrom were subjected to a competitive binding assay against purified CaM and a CaM biosensor to assess the amounts of unoccupied CaM-binding sites. LV cellular composition was assessed by immunohistochemistry. KEY FINDINGS LV eluants processed from sham animals reduce biosensor response by ~32%, indicating baseline presence of unoccupied CaM-binding sites and a limiting CaM equilibrium. Ovariectomy exacerbates the limiting CaM equilibrium, reducing biosensor response by ~65%. 17β-estradiol treatment equalizes the difference between sham and ovariectomized animals. These changes reflect whole tissue responses and are not mirrored by changes in total surface areas of cardiomyocytes and fibroblasts. Consistently, Ca2+-dependent, but not Ca2+-independent, interaction between CaM and the cardiac inositol trisphosphate receptor (IP3R) is reduced following ovariectomy and is restored by subsequent 17β-estradiol treatment. SIGNIFICANCE Our assay provides a new parameter to assess tissue CaM equilibrium. The exacerbated limiting CaM equilibrium following estrogen loss may contribute to cardiac morbidity and is prevented by estrogen treatment.
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Affiliation(s)
- Kyle Kaster
- Department of Physiology & Pharmacology, Des Moines University Osteopathic Medical Center, IA 50312, United States
| | - John Patton
- Department of Physiology & Pharmacology, Des Moines University Osteopathic Medical Center, IA 50312, United States
| | - Sarah Clayton
- Department of Physiology & Pharmacology, Des Moines University Osteopathic Medical Center, IA 50312, United States
| | - Eric Wauson
- Department of Physiology & Pharmacology, Des Moines University Osteopathic Medical Center, IA 50312, United States
| | - Jennifer Giles
- Department of Physiology & Pharmacology, Des Moines University Osteopathic Medical Center, IA 50312, United States
| | - Quang-Kim Tran
- Department of Physiology & Pharmacology, Des Moines University Osteopathic Medical Center, IA 50312, United States.
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Petazzi RA, Aji AK, Chiantia S. Fluorescence microscopy methods for the study of protein oligomerization. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2020; 169:1-41. [DOI: 10.1016/bs.pmbts.2019.12.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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7
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Janovič T, Stojaspal M, Veverka P, Horáková D, Hofr C. Human Telomere Repeat Binding Factor TRF1 Replaces TRF2 Bound to Shelterin Core Hub TIN2 when TPP1 Is Absent. J Mol Biol 2019; 431:3289-3301. [DOI: 10.1016/j.jmb.2019.05.038] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 05/22/2019] [Accepted: 05/23/2019] [Indexed: 12/17/2022]
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8
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Ng XW, Sampath K, Wohland T. Fluorescence Correlation and Cross-Correlation Spectroscopy in Zebrafish. Methods Mol Biol 2019; 1863:67-105. [PMID: 30324593 DOI: 10.1007/978-1-4939-8772-6_5] [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] [Indexed: 02/10/2023]
Abstract
There has been increasing interest in biophysical studies on live organisms to gain better insights into physiologically relevant biological events at the molecular level. Zebrafish (Danio rerio) is a viable vertebrate model to study such events due to its genetic and evolutionary similarities to humans, amenability to less invasive fluorescence techniques owing to its transparency and well-characterized genetic manipulation techniques. Fluorescence techniques used to probe biomolecular dynamics and interactions of molecules in live zebrafish embryos are therefore highly sought-after to bridge molecular and developmental events. Fluorescence correlation and cross-correlation spectroscopy (FCS and FCCS) are two robust techniques that provide molecular level information on dynamics and interactions respectively. Here, we detail the steps for applying confocal FCS and FCCS, in particular single-wavelength FCCS (SW-FCCS), in live zebrafish embryos, beginning with sample preparation, instrumentation, calibration, and measurements on the FCS/FCCS instrument and ending with data analysis.
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Affiliation(s)
- Xue Wen Ng
- Department of Chemistry and Centre for Bioimaging Sciences, National University of Singapore, Singapore, Singapore
| | - Karuna Sampath
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, UK
| | - Thorsten Wohland
- Department of Chemistry and Centre for Bioimaging Sciences, National University of Singapore, Singapore, Singapore. .,Department of Biological Sciences, National University of Singapore, Singapore, Singapore.
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Ehlers K, Clements R, VerMeer M, Giles J, Tran QK. Novel regulations of the angiotensin II receptor type 1 by calmodulin. Biochem Pharmacol 2018; 152:187-200. [PMID: 29605626 DOI: 10.1016/j.bcp.2018.03.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Accepted: 03/27/2018] [Indexed: 01/10/2023]
Abstract
The angiotensin II receptor type 1 (AT1R) mediates many Ca2+-dependent actions of angiotensin II (AngII). Calmodulin (CaM) is a key transducer of Ca2+ signals in cells. Two locations on the receptor's submembrane domains (SMD) 3 and 4 are known to interact with CaM. However, the binding sites for CaM, biochemical properties of the interactions, and their functional impact are not fully understood. Using a FRET-based screening method, we identified a new binding site for CaM on SMD2 (a.a. 125-141), in addition to SMD3 and the juxtamembranous region of SMD4 (SMD4JM, a.a., 309-327). Simultaneous measurements of CaM binding and free Ca2+ show that the interactions are Ca2+-dependent, with disparate Kd and EC50(Ca2+) values within the physiological range of cytoplasmic Ca2+. Full interaction between CaM and SMD3 requires the entire domain (a.a. 215-242) and has an EC50(Ca2+) value in the range of resting cytoplasmic Ca2+, suggesting AT1R-CaM interaction can occur in resting conditions in cells. AngII induces robust ERK1/2 phosphorylation in primary vascular smooth muscle cells. This effect is suppressed by AT1R inhibitor losartan and virtually abolished by CaM antagonist W-7. AngII-induced ERK1/2 phosphorylation is suppressed in cells expressing mutant AT1R with reduced CaM binding at each identified binding domain. AngII triggers transient Ca2+ signals in cells expressing wild-type AT1R. These signals are reduced in cells expressing mutant AT1R with reduced CaM binding at SMD3 or SMD4JM, but are very slow-rising, low amplitude signal in cells expressing AT1R with reduced CaM binding at SMD2. The data indicate that CaM interactions with AT1R can occur at various domains, with different affinities, at different physiological Ca2+ levels, and are important for AT1R-mediated signaling.
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Affiliation(s)
- Kevin Ehlers
- Department of Physiology & Pharmacology, Des Moines University Osteopathic Medical Center, 3200 Grand Avenue, Des Moines, IA 50312, United States
| | - Robert Clements
- Department of Physiology & Pharmacology, Des Moines University Osteopathic Medical Center, 3200 Grand Avenue, Des Moines, IA 50312, United States
| | - Mark VerMeer
- Department of Physiology & Pharmacology, Des Moines University Osteopathic Medical Center, 3200 Grand Avenue, Des Moines, IA 50312, United States
| | - Jennifer Giles
- Department of Physiology & Pharmacology, Des Moines University Osteopathic Medical Center, 3200 Grand Avenue, Des Moines, IA 50312, United States
| | - Quang-Kim Tran
- Department of Physiology & Pharmacology, Des Moines University Osteopathic Medical Center, 3200 Grand Avenue, Des Moines, IA 50312, United States.
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Schwille P. There and back again: from the origin of life to single molecules. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2018; 47:493-498. [PMID: 29569181 PMCID: PMC5982444 DOI: 10.1007/s00249-018-1295-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 03/08/2018] [Accepted: 03/13/2018] [Indexed: 11/27/2022]
Abstract
What is life? There is hardly a more fundamental question raised by aspiring researchers, and one less prone to ever be answered in a scientifically satisfying way. In the long, productive and highly influential period of research following his Nobel-recognised work on relaxation kinetics, Manfred Eigen made seminal contributions towards a quantifiable definition of life, with a strong focus on its evolutionary character. In the last years of his time as an active researcher, however, he devoted himself to another, purely experimental topic: the detection and analysis of single biomolecules in aqueous solution. In this short review, I will give an overview of the groundbreaking contributions to the field of single molecule research made by Eigen and coworkers, and show that both, in its intrinsic motivation, and in its consequences, single molecule research strongly relates to the question of the physical-chemical essence of life. In fact, research on living systems with single molecule sensitivity will always refer the researcher to the question of the simplest possible representation, and thus the origin, of any biological phenomenon.
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Affiliation(s)
- Petra Schwille
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152, Martinsried, Germany.
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Kaliszewski MJ, Shi X, Hou Y, Lingerak R, Kim S, Mallory P, Smith AW. Quantifying membrane protein oligomerization with fluorescence cross-correlation spectroscopy. Methods 2018; 140-141:40-51. [PMID: 29448037 DOI: 10.1016/j.ymeth.2018.02.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 12/17/2017] [Accepted: 02/07/2018] [Indexed: 01/27/2023] Open
Abstract
Fluorescence cross-correlation spectroscopy (FCCS) is an advanced fluorescence technique that can quantify protein-protein interactions in vivo. Due to the dynamic, heterogeneous nature of the membrane, special considerations must be made to interpret FCCS data accurately. In this study, we describe a method to quantify the oligomerization of membrane proteins tagged with two commonly used fluorescent probes, mCherry (mCH) and enhanced green (eGFP) fluorescent proteins. A mathematical model is described that relates the relative cross-correlation value (fc) to the degree of oligomerization. This treatment accounts for mismatch in the confocal volumes, combinatoric effects of using two fluorescent probes, and the presence of non-fluorescent probes. Using this model, we calculate a ladder of fc values which can be used to determine the oligomer state of membrane proteins from live-cell experimental data. Additionally, a probabilistic mathematical simulation is described to resolve the affinity of different dimeric and oligomeric protein controls.
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Affiliation(s)
| | - Xiaojun Shi
- Department of Chemistry, University of Akron, Akron, OH 44325, USA
| | - Yixuan Hou
- Food Animal Health Research Program, Ohio Agriculture Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, OH 44691, USA
| | - Ryan Lingerak
- Department of Biology, University of Akron, Akron, OH 44325, USA
| | - Soyeon Kim
- Department of Chemistry, University of Akron, Akron, OH 44325, USA
| | - Paul Mallory
- Department of Chemistry, University of Akron, Akron, OH 44325, USA
| | - Adam W Smith
- Department of Chemistry, University of Akron, Akron, OH 44325, USA.
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12
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Heidarinejad M, Nakamura H, Inoue T. Stimulation-induced changes in diffusion and structure of calmodulin and calmodulin-dependent protein kinase II proteins in neurons. Neurosci Res 2018; 136:13-32. [PMID: 29395358 DOI: 10.1016/j.neures.2018.01.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2017] [Revised: 01/11/2018] [Accepted: 01/11/2018] [Indexed: 11/28/2022]
Abstract
Calcium/calmodulin-dependent protein kinase II (CaMKII) and calmodulin (CaM) play essential roles in synaptic plasticity, which is an elementary process of learning and memory. In this study, fluorescence correlation spectroscopy (FCS) revealed diffusion properties of CaM, CaMKIIα and CaMKIIβ proteins in human embryonic kidney 293 (HEK293) cells and hippocampal neurons. A simultaneous multiple-point FCS recording system was developed on a random-access two-photon microscope, which facilitated efficient analysis of molecular dynamics in neuronal compartments. The diffusion of CaM in neurons was slower than that in HEK293 cells at rest, while the diffusion in stimulated neurons was accelerated and indistinguishable from that in HEK293 cells. This implied that activity-dependent binding partners of CaM exist in neurons, which slow down the diffusion at rest. Diffusion properties of CaMKIIα and β proteins implied that major populations of these proteins exist as holoenzymatic forms. Upon stimulation of neurons, the diffusion of CaMKIIα and β proteins became faster with reduced particle brightness, indicating drastic structural changes of the proteins such as dismissal from holoenzyme structure and further fragmentation.
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Affiliation(s)
- Morteza Heidarinejad
- Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan.
| | - Hideki Nakamura
- Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan.
| | - Takafumi Inoue
- Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan.
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13
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Suppression of store-operated Ca2+ entry by activation of GPER: contribution to a clamping effect on endothelial Ca2+ signaling. Biochem J 2017; 474:3627-3642. [DOI: 10.1042/bcj20170630] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 09/15/2017] [Accepted: 09/18/2017] [Indexed: 12/20/2022]
Abstract
The G protein-coupled estrogen receptor 1 (GPER, formerly also known as GPR30) modulates many Ca2+-dependent activities in endothelial cells. However, the underlying mechanisms are poorly understood. We recently reported that GPER acts to prolong cytoplasmic Ca2+ signals by interacting with and promoting inhibitory phosphorylation of the plasma membrane Ca2+-ATPase. In the present study, we examined the role of GPER activation in modulating store-operated Ca2+ entry (SOCE) via effects on the stromal interaction molecule 1 (STIM1). GPER activation by agonist G-1 reduces the peak but prolongs the plateau of bradykinin-induced Ca2+ signals in primary endothelial cells. G-1 dose-dependently inhibits thapsigargin-induced SOCE measured by the Mn2+ quenching method. GPER heterologous expression reduces SOCE, which is further pronounced by G-1 treatment. Consistently, GPER gene silencing in endothelial cells is associated with an increase in SOCE. Treatment with G-1 reduces puncta formation by STIM1 triggered by the activation of SOCE. The effect of GPER activation to inhibit SOCE is not affected by combined nonphosphorylatable substitutions at serines 486 and 668 on STIM1, but is substantially reduced by similar substitutions at serines 575, 608 and 621. Taken together with our recently reported inhibitory actions of GPER on Ca2+ efflux, the current data contribute to a model in which GPER acts to clamp agonist-induced cytoplasmic Ca2+ signals. Kinetic modeling based on current and reported data is used to estimate the overall effect of GPER activation on point activity of endothelial nitric oxide synthase during the time course of agonist-induced total Ca2+ signals.
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14
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Johnson CK, Harms GS. Tracking and localization of calmodulin in live cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2017-26. [DOI: 10.1016/j.bbamcr.2016.04.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 04/19/2016] [Accepted: 04/20/2016] [Indexed: 01/20/2023]
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15
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Hoffman L, Wang X, Sanabria H, Cheung MS, Putkey JA, Waxham MN. Relative Cosolute Size Influences the Kinetics of Protein-Protein Interactions. Biophys J 2016; 109:510-20. [PMID: 26244733 DOI: 10.1016/j.bpj.2015.06.043] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 05/29/2015] [Accepted: 06/22/2015] [Indexed: 12/18/2022] Open
Abstract
Protein signaling occurs in crowded intracellular environments, and while high concentrations of macromolecules are postulated to modulate protein-protein interactions, analysis of their impact at each step of the reaction pathway has not been systematically addressed. Potential cosolute-induced alterations in target association are particularly important for a signaling molecule like calmodulin (CaM), where competition among >300 targets governs which pathways are selectively activated. To explore how high concentrations of cosolutes influence CaM-target affinity and kinetics, we methodically investigated each step of the CaM-target binding mechanism under crowded or osmolyte-rich environments mimicked by ficoll-70, dextran-10, and sucrose. All cosolutes stabilized compact conformers of CaM and modulated association kinetics by affecting diffusion and rates of conformational change; however, the results showed that differently sized molecules had variable effects to enhance or impede unique steps of the association pathway. On- and off-rates were modulated by all cosolutes in a compensatory fashion, producing little change in steady-state affinity. From this work insights were gained on how high concentrations of inert crowding agents and osmolytes fit into a kinetic framework to describe protein-protein interactions relevant for cellular signaling.
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Affiliation(s)
- Laurel Hoffman
- Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Texas
| | - Xu Wang
- Department of Biochemistry and Molecular Biology, University of Texas Medical School at Houston, Houston, Texas
| | - Hugo Sanabria
- Department of Physics and Astronomy, Clemson University, Clemson, South Carolina
| | - Margaret S Cheung
- Department of Physics, University of Houston, Houston, Texas; The Center for Theoretical Biological Physics, Rice University, Houston, Texas
| | - John A Putkey
- Department of Biochemistry and Molecular Biology, University of Texas Medical School at Houston, Houston, Texas
| | - M Neal Waxham
- Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Texas.
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16
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Tran QK, Firkins R, Giles J, Francis S, Matnishian V, Tran P, VerMeer M, Jasurda J, Burgard MA, Gebert-Oberle B. Estrogen Enhances Linkage in the Vascular Endothelial Calmodulin Network via a Feedforward Mechanism at the G Protein-coupled Estrogen Receptor 1. J Biol Chem 2016; 291:10805-23. [PMID: 26987903 DOI: 10.1074/jbc.m115.697334] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Indexed: 12/13/2022] Open
Abstract
Estrogen exerts many effects on the vascular endothelium. Calmodulin (CaM) is the transducer of Ca(2+) signals and is a limiting factor in cardiovascular tissues. It is unknown whether and how estrogen modifies endothelial functions via the network of CaM-dependent proteins. Here we show that 17β-estradiol (E2) up-regulates total CaM level in endothelial cells. Concurrent measurement of Ca(2+) and Ca(2+)-CaM indicated that E2 also increases free Ca(2+)-CaM. Pharmacological studies, gene silencing, and receptor expression-specific cell studies indicated that the G protein-coupled estrogen receptor 1 (GPER/GPR30) mediates these effects via transactivation of EGFR and subsequent MAPK activation. The outcomes were then examined on four distinct members of the intracellular CaM target network, including GPER/GPR30 itself and estrogen receptor α, the plasma membrane Ca(2+)-ATPase (PMCA), and endothelial nitric-oxide synthase (eNOS). E2 substantially increases CaM binding to estrogen receptor α and GPER/GPR30. Mutations that reduced CaM binding to GPER/GPR30 in separate binding domains do not affect GPER/GPR30-Gβγ preassociation but decrease GPER/GPR30-mediated ERK1/2 phosphorylation. E2 increases CaM-PMCA association, but the expected stimulation of Ca(2+) efflux is reversed by E2-stimulated tyrosine phosphorylation of PMCA. These effects sustain Ca(2+) signals and promote Ca(2+)-dependent CaM interactions with other CaM targets. Consequently, E2 doubles CaM-eNOS interaction and also promotes dual phosphorylation of eNOS at Ser-617 and Ser-1179. Calculations using in-cell and in vitro data revealed substantial individual and combined contribution of these effects to total eNOS activity. Taken together, E2 generates a feedforward loop via GPER/GPR30, which enhances Ca(2+)/CaM signals and functional linkage in the endothelial CaM target network.
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Affiliation(s)
- Quang-Kim Tran
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Rachel Firkins
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Jennifer Giles
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Sarah Francis
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Vahe Matnishian
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Phuong Tran
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Mark VerMeer
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Jake Jasurda
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Michelle Ann Burgard
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
| | - Briana Gebert-Oberle
- From the Department of Physiology and Pharmacology, College of Osteopathic Medicine, Des Moines University, Des Moines, Iowa 50312
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17
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Goossens K, Prior M, Pacheco V, Willbold D, Müllen K, Enderlein J, Hofkens J, Gregor I. Accurate Diffusion Coefficients of Organosoluble Reference Dyes in Organic Media Measured by Dual-Focus Fluorescence Correlation Spectroscopy. ACS NANO 2015; 9:7360-7373. [PMID: 26144863 DOI: 10.1021/acsnano.5b02371] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Dual-focus fluorescence correlation spectroscopy (2fFCS) is a versatile method to determine accurate diffusion coefficients of fluorescent species in an absolute, reference-free manner. Whereas (either classical or dual-focus) FCS has been employed primarily in the life sciences and thus in aqueous environments, it is increasingly being used in materials chemistry, as well. These measurements are often performed in nonaqueous media such as organic solvents. However, the diffusion coefficients of reference dyes in organic solvents are not readily available. For this reason we determined the translational diffusion coefficients of several commercially available organosoluble fluorescent dyes by means of 2fFCS. The selected dyes and organic solvents span the visible spectrum and a broad range of refractive indices, respectively. The diffusion coefficients can be used as absolute reference values for the calibration of experimental FCS setups, allowing quantitative measurements to be performed. We show that reliable information about the hydrodynamic dimensions of the fluorescent species (including noncommercial compounds) within organic media can be extracted from the 2fFCS data.
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Affiliation(s)
- Karel Goossens
- †KU Leuven, Department of Chemistry, Celestijnenlaan 200F (PO Box 2404), 3001 Heverlee, Belgium
- ‡Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), 101-dong, UNIST-gil 50, Eonyang-eup, Ulju-gun, Ulsan 689-798, Republic of Korea
| | - Mira Prior
- §Georg August University, Third Institute of Physics, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Victor Pacheco
- ⊥Research Centre Jülich, Institute of Complex Systems: Structural Biochemistry (ICS-6), Wilhelm-Johnen-Straße, 52425 Jülich, Germany
- ∥Albert Ludwigs University, Institute for Macromolecular Chemistry, Hermann-Staudinger-Haus, Stefan-Meier-Straße 31, 79104 Freiburg, Germany
| | - Dieter Willbold
- ⊥Research Centre Jülich, Institute of Complex Systems: Structural Biochemistry (ICS-6), Wilhelm-Johnen-Straße, 52425 Jülich, Germany
- #Heinrich Heine University, Institute for Physical Biology, Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Klaus Müllen
- ∇Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Jörg Enderlein
- §Georg August University, Third Institute of Physics, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Johan Hofkens
- †KU Leuven, Department of Chemistry, Celestijnenlaan 200F (PO Box 2404), 3001 Heverlee, Belgium
| | - Ingo Gregor
- §Georg August University, Third Institute of Physics, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
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18
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Neurogranin regulates CaM dynamics at dendritic spines. Sci Rep 2015; 5:11135. [PMID: 26084473 PMCID: PMC4471661 DOI: 10.1038/srep11135] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 05/18/2015] [Indexed: 11/18/2022] Open
Abstract
Calmodulin (CaM) plays a key role in synaptic function and plasticity due to its ability to mediate Ca2+ signaling. Therefore, it is essential to understand the dynamics of CaM at dendritic spines. In this study we have explored CaM dynamics using live-cell confocal microscopy and fluorescence recovery after photobleaching (FRAP) to study CaM diffusion. We find that only a small fraction of CaM in dendritic spines is immobile. Furthermore, the diffusion rate of CaM was regulated by neurogranin (Ng), a CaM-binding protein enriched at dendritic spines. Interestingly, Ng did not influence the immobile fraction of CaM at recovery plateau. We have previously shown that Ng enhances synaptic strength in a CaM-dependent manner. Taken together, these data indicate that Ng-mediated enhancement of synaptic strength is due to its ability to target, rather than sequester, CaM within dendritic spines.
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19
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Orban-Glaß I, Voskoboynikova N, Busch KB, Klose D, Rickert C, Mosslehy W, Roder F, Wilkens V, Piehler J, Engelhard M, Steinhoff HJ, Klare JP. Clustering and dynamics of phototransducer signaling domains revealed by site-directed spin labeling electron paramagnetic resonance on SRII/HtrII in membranes and nanodiscs. Biochemistry 2014; 54:349-62. [PMID: 25489970 DOI: 10.1021/bi501160q] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In halophilic archaea the photophobic response is mediated by the membrane-embedded 2:2 photoreceptor/-transducer complex SRII/HtrII, the latter being homologous to the bacterial chemoreceptors. Both systems bias the rotation direction of the flagellar motor via a two-component system coupled to an extended cytoplasmic signaling domain formed by a four helical antiparallel coiled-coil structure. For signal propagation by the HAMP domains connecting the transmembrane and cytoplasmic domains, it was suggested that a two-state thermodynamic equilibrium found for the first HAMP domain in NpSRII/NpHtrII is shifted upon activation, yet signal propagation along the coiled-coil transducer remains largely elusive, including the activation mechanism of the coupled kinase CheA. We investigated the dynamic and structural properties of the cytoplasmic tip domain of NpHtrII in terms of signal transduction and putative oligomerization using site-directed spin labeling electron paramagnetic resonance spectroscopy. We show that the cytoplasmic tip domain of NpHtrII is engaged in a two-state equilibrium between a dynamic and a compact conformation like what was found for the first HAMP domain, thus strengthening the assumption that dynamics are the language of signal transfer. Interspin distance measurements in membranes and on isolated 2:2 photoreceptor/transducer complexes in nanolipoprotein particles provide evidence that archaeal photoreceptor/-transducer complexes analogous to chemoreceptors form trimers-of-dimers or higher-order assemblies even in the absence of the cytoplasmic components CheA and CheW, underlining conservation of the overall mechanistic principles underlying archaeal phototaxis and bacterial chemotaxis systems. Furthermore, our results revealed a significant influence of the NpHtrII signaling domain on the NpSRII photocycle kinetics, providing evidence for a conformational coupling of SRII and HtrII in these complexes.
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Affiliation(s)
- Ioan Orban-Glaß
- Macromolecular Structure Group, Department of Physics, University of Osnabrück , Barbarastrasse 7, 49076 Osnabrück, Germany
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20
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Suthari P, P HK, Doddi S, Bangal PR. Investigation of supramolecular stoichiometry and dynamic for inclusion complex of water soluble porphyrin with cucurbit[7]uril by fluorescence correlation spectroscopy. J Photochem Photobiol A Chem 2014. [DOI: 10.1016/j.jphotochem.2014.04.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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21
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Tran QK, VerMeer M. Biosensor-based approach identifies four distinct calmodulin-binding domains in the G protein-coupled estrogen receptor 1. PLoS One 2014; 9:e89669. [PMID: 24586950 PMCID: PMC3931812 DOI: 10.1371/journal.pone.0089669] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 01/22/2014] [Indexed: 01/24/2023] Open
Abstract
The G protein-coupled estrogen receptor 1 (GPER) has been demonstrated to participate in many cellular functions, but its regulatory inputs are not clearly understood. Here we describe a new approach that identifies GPER as a calmodulin-binding protein, locates interaction sites, and characterizes their binding properties. GPER coimmunoprecipitates with calmodulin in primary vascular smooth muscle cells under resting conditions, which is enhanced upon acute treatment with either specific ligands or a Ca(2+)-elevating agent. To confirm direct interaction and locate the calmodulin-binding domain(s), we designed a series of FRET biosensors that consist of enhanced cyan and yellow fluorescent proteins flanking each of GPER's submembrane domains (SMDs). Responses of these biosensors showed that all four submembrane domains directly bind calmodulin. Modifications of biosensor linker identified domains that display the strongest calmodulin-binding affinities and largest biosensor dynamics, including a.a. 83-93, 150-175, 242-259, 330-351, corresponding respectively to SMDs 1, 2, 3, and the juxta-membranous section of SMD4. These biosensors bind calmodulin in a strictly Ca(2+)-dependent fashion and with disparate affinities in the order SMD2>SMD4>SMD3>SMD1, apparent K d values being 0.44 ± 0.03, 1.40 ± 0.16, 8.01 ± 0.29, and 136.62 ± 6.56 µM, respectively. Interestingly, simultaneous determinations of biosensor responses and suitable Ca(2+) indicators identified separate Ca(2+) sensitivities for their interactions with calmodulin. SMD1-CaM complexes display a biphasic Ca(2+) response, representing two distinct species (SMD1 sp1 and SMD1 sp2) with drastically different Ca(2+) sensitivities. The Ca(2+) sensitivities of CaM-SMDs interactions follow the order SMD1sp1>SMD4>SMD2>SMD1sp2>SMD3, EC50(Ca(2+)) values being 0.13 ± 0.02, 0.75 ± 0.05, 2.38 ± 0.13, 3.71 ± 0.13, and 5.15 ± 0.25 µM, respectively. These data indicate that calmodulin may regulate GPER-dependent signaling at the receptor level through multiple interaction sites. FRET biosensors represent a simple method to identify unknown calmodulin-binding domains in G protein-coupled receptors and to quantitatively assess binding properties.
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Affiliation(s)
- Quang-Kim Tran
- Department of Physiology & Pharmacology, Des Moines University Osteopathic Medical Center, Des Moines, Iowa, United States of America
- * E-mail:
| | - Mark VerMeer
- Department of Physiology & Pharmacology, Des Moines University Osteopathic Medical Center, Des Moines, Iowa, United States of America
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22
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Ly S, Altman R, Petrlova J, Lin Y, Hilt S, Huser T, Laurence TA, Voss JC. Binding of apolipoprotein E inhibits the oligomer growth of amyloid-β peptide in solution as determined by fluorescence cross-correlation spectroscopy. J Biol Chem 2013; 288:11628-35. [PMID: 23430745 DOI: 10.1074/jbc.m112.411900] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
One of the primary neuropathological hallmarks of Alzheimer disease is the presence of extracellular amyloid plaques resulting from the aggregation of amyloid-β (Aβ) peptides. The intrinsic disorder of the Aβ peptide drives self-association and progressive reordering of the conformation in solution, and this dynamic distribution of Aβ complicates biophysical studies. This property poses a challenge for understanding the interaction of Aβ with apolipoprotein E (apoE). ApoE plays a pivotal role in the aggregation and clearance of Aβ peptides in the brain, and the ε4 allele of APOE is the most significant known genetic modulator of Alzheimer risk. Understanding the interaction between apoE and Aβ will provide insight into the mechanism by which different apoE isoforms determine Alzheimer disease risk. Here we applied alternating laser excitation fluorescence cross-correlation spectroscopy to observe the single molecule interaction of Aβ with apoE in the hydrated state. The diffusion time of freely diffusing Aβ in the absence of apoE shows significant self-aggregation, whereas in the presence of apoE, binding of the protein results in a more stable complex. These results show that apoE slows down the oligomerization of Aβ in solution and provide direct insight into the process by which apoE influences the deposition and clearance of Aβ peptides in the brain. Furthermore, by developing an approach to remove signals arising from very large Aβ aggregates, we show that real-time single particle observations provide access to information regarding the fraction of apoE bound and the stoichiometry of apoE and Aβ in the complex.
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Affiliation(s)
- Sonny Ly
- Physical and Life Science Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
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23
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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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24
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Bacia K, Petrášek Z, Schwille P. Correcting for spectral cross-talk in dual-color fluorescence cross-correlation spectroscopy. Chemphyschem 2012; 13:1221-31. [PMID: 22344749 PMCID: PMC3495304 DOI: 10.1002/cphc.201100801] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 12/29/2011] [Indexed: 11/07/2022]
Abstract
Dual-color fluorescence cross-correlation spectroscopy (dcFCCS) allows one to quantitatively assess the interactions of mobile molecules labeled with distinct fluorophores. The technique is widely applied to both reconstituted and live-cell biological systems. A major drawback of dcFCCS is the risk of an artifactual false-positive or overestimated cross-correlation amplitude arising from spectral cross-talk. Cross-talk can be reduced or prevented by fast alternating excitation, but the technology is not easily implemented in standard commercial setups. An experimental strategy is devised that does not require specialized hardware and software for recognizing and correcting for cross-talk in standard dcFCCS. The dependence of the cross-talk on particle concentrations and brightnesses is quantitatively confirmed. Moreover, it is straightforward to quantitatively correct for cross-talk using quickly accessible parameters, that is, the measured (apparent) fluorescence count rates and correlation amplitudes. Only the bleed-through ratio needs to be determined in a calibration measurement. Finally, the limitations of cross-talk correction and its influence on experimental error are explored.
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Affiliation(s)
- Kirsten Bacia
- HALOmem, University of Halle, Kurt-Mothes-Str. 3, 06120 Halle, Germany.
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25
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Schmidt H. Three functional facets of calbindin D-28k. Front Mol Neurosci 2012; 5:25. [PMID: 22435048 PMCID: PMC3304297 DOI: 10.3389/fnmol.2012.00025] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 02/14/2012] [Indexed: 11/13/2022] Open
Abstract
Many neurons of the vertebrate central nervous system (CNS) express the Ca2+ binding protein calbindin D-28k (CB), including important projection neurons like cerebellar Purkinje cells but also neocortical interneurons. CB has moderate cytoplasmic mobility and comprises at least four EF-hands that function in Ca2+ binding with rapid to intermediate kinetics and affinity. Classically it was viewed as a pure Ca2+ buffer important for neuronal survival. This view was extended by showing that CB is a critical determinant in the control of synaptic Ca2+ dynamics, presumably with strong impact on plasticity and information processing. Already 30 years ago, in vitro studies suggested that CB could have an additional Ca2+ sensor function, like its prominent acquaintance calmodulin (CaM). More recent work substantiated this hypothesis, revealing direct CB interactions with several target proteins. Different from a classical sensor, however, CB appears to interact with its targets both, in its Ca2+-loaded and Ca2+-free forms. Finally, CB has been shown to be involved in buffered transport of Ca2+, in neurons but also in kidney. Thus, CB serves a threefold function as buffer, transporter and likely as a non-canonical sensor.
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Affiliation(s)
- Hartmut Schmidt
- Medical Faculty, Carl-Ludwig Institute for Physiology, University of Leipzig Leipzig, Germany.
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26
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Strömqvist J, Johansson S, Xu L, Ohsugi Y, Andersson K, Muto H, Kinjo M, Höglund P, Widengren J. A modified FCCS procedure applied to Ly49A-MHC class I cis-interaction studies in cell membranes. Biophys J 2011; 101:1257-69. [PMID: 21889464 PMCID: PMC3164190 DOI: 10.1016/j.bpj.2011.06.057] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 06/10/2011] [Accepted: 06/27/2011] [Indexed: 11/23/2022] Open
Abstract
The activity of natural killer (NK) cells is regulated by a fine-tuned balance between activating and inhibitory receptors. Dual-color fluorescence cross-correlation spectroscopy (FCCS) was used to directly demonstrate a so-called cis-interaction between a member of the inhibitory NK cell receptor family Ly49 (Ly49A), and its ligand, the major histocompatibility complex (MHC) class I, within the plasma membrane of the same cell. By a refined FCCS model, calibrated by positive and negative control experiments on cells from the same lymphoid cell line, concentrations and diffusion coefficients of free and interacting proteins could be determined on a collection of cells. Using the intrinsic intercellular variation of their expression levels for titration, it was found that the fraction of Ly49A receptors bound in cis increase with increasing amounts of MHC class I ligand. This increase shows a tendency to be more abrupt than for a diffusion limited - three dimensional bimolecular reaction, which most likely reflects the two-dimensional confinement of the reaction. For the Ly49A- MHC class I interaction it indicates that within a critical concentration range the local concentration level of MHC class I can provide a distinct regulation mechanism of the NK cell activity.
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Affiliation(s)
- Johan Strömqvist
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, AlbaNova University Center, Stockholm, Sweden
| | - Sofia Johansson
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, AlbaNova University Center, Stockholm, Sweden
| | - Lei Xu
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, AlbaNova University Center, Stockholm, Sweden
| | - Yu Ohsugi
- Laboratory of Supramolecular Biophysics, Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan
| | - Katja Andersson
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Hideki Muto
- Laboratory of Supramolecular Biophysics, Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan
| | - Masataka Kinjo
- Laboratory of Supramolecular Biophysics, Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan
| | - Petter Höglund
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Jerker Widengren
- Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, AlbaNova University Center, Stockholm, Sweden
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Colocalization of protein kinase A with adenylyl cyclase enhances protein kinase A activity during induction of long-lasting long-term-potentiation. PLoS Comput Biol 2011; 7:e1002084. [PMID: 21738458 PMCID: PMC3127802 DOI: 10.1371/journal.pcbi.1002084] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Accepted: 04/27/2011] [Indexed: 11/25/2022] Open
Abstract
The ability of neurons to differentially respond to specific temporal and spatial input patterns underlies information storage in neural circuits. One means of achieving spatial specificity is to restrict signaling molecules to particular subcellular compartments using anchoring molecules such as A-Kinase Anchoring Proteins (AKAPs). Disruption of protein kinase A (PKA) anchoring to AKAPs impairs a PKA-dependent form of long term potentiation (LTP) in the hippocampus. To investigate the role of localized PKA signaling in LTP, we developed a stochastic reaction-diffusion model of the signaling pathways leading to PKA activation in CA1 pyramidal neurons. Simulations investigated whether the role of anchoring is to locate kinases near molecules that activate them, or near their target molecules. The results show that anchoring PKA with adenylyl cyclase (which produces cAMP that activates PKA) produces significantly greater PKA activity, and phosphorylation of both inhibitor-1 and AMPA receptor GluR1 subunit on S845, than when PKA is anchored apart from adenylyl cyclase. The spatial microdomain of cAMP was smaller than that of PKA suggesting that anchoring PKA near its source of cAMP is critical because inactivation by phosphodiesterase limits diffusion of cAMP. The prediction that the role of anchoring is to colocalize PKA near adenylyl cyclase was confirmed by experimentally rescuing the deficit in LTP produced by disruption of PKA anchoring using phosphodiesterase inhibitors. Additional experiments confirm the model prediction that disruption of anchoring impairs S845 phosphorylation produced by forskolin-induced synaptic potentiation. Collectively, these results show that locating PKA near adenylyl cyclase is a critical function of anchoring. The hippocampus is a part of the cerebral cortex involved in formation of certain types of long term memories. Activity-dependent change in the strength of neuronal connections in the hippocampus, known as synaptic plasticity, is one mechanism used to store memories. The ability to form crisp and distinguishable memories of different events implies that learning produces plasticity of specific and distinct subsets of synapses within each neuron. Synaptic activity leads to production of intracellular signaling molecules, which ultimately cause changes in the properties of the synapses. The requirement for synaptic specificity seems incompatible with the diffusibility of intracellular signaling molecules. Anchoring proteins restrict signaling molecules to particular subcellular compartments thereby combating the indiscriminate spread of intracellular signaling molecules. To investigate whether the critical function of anchoring proteins is to localize proteins near their activators or their targets, we developed a stochastic reaction-diffusion model of signaling pathways leading to synaptic plasticity in hippocampal neurons. Simulations demonstrate that colocalizing proteins with their activator molecules is more important due to inactivation mechanisms that limit the spatial extent of the activator molecules.
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28
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Dilipkumar S, Diaspro A, Mondal PP. Spatial filter based 3D resolution improvement and polarization properties of multiphoton multiple-excitation-spot-optical microscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2011; 82:063705. [PMID: 21721700 DOI: 10.1063/1.3600795] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Three-dimensional (3D) resolution improvement in multi-photon multiple-excitation-spot-optical microscopy is proposed. Specially designed spatial filter is employed for improving the overall 3D resolution of the imaging system. An improvement up to a factor of 14.5 and sub-femto liter volume excitation is achieved. The system shows substantial sidelobe reduction (<4%) due to the non-linear intensity dependence of multiphoton process. Polarization effect on x-oriented and freely rotating dipoles shows dramatic change in the field distribution at the focal-plane. The resulting point-spread function has the ability to produce several strongly localized polarization dependent field patterns which may find applications in optical engineering and bioimaging.
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Affiliation(s)
- Shilpa Dilipkumar
- Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560012, India
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29
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Chen A, Eberle MM, Lunt EJ, Liu S, Leake K, Rudenko MI, Hawkins AR, Schmidt H. Dual-color fluorescence cross-correlation spectroscopy on a planar optofluidic chip. LAB ON A CHIP 2011; 11:1502-1506. [PMID: 21340094 DOI: 10.1039/c0lc00401d] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Fluorescence cross-correlation spectroscopy (FCCS) is a highly sensitive fluorescence technique with distinct advantages in many bioanalytical applications involving interaction and binding of multiple components. Due to the use of multiple beams, bulk optical FCCS setups require delicate and complex alignment procedures. We demonstrate the first implementation of dual-color FCCS on a planar, integrated optofluidic chip based on liquid-core waveguides that can guide liquid and light simultaneously. In this configuration, the excitation beams are delivered in predefined locations and automatically aligned within the excitation waveguides. We implement two canonical applications of FCCS in the optofluidic lab-on-chip environment: particle colocalization and binding/dissociation dynamics. Colocalization is demonstrated in the detection and discrimination of single-color and double-color fluorescently labeled nanobeads. FCCS in combination with fluorescence resonance energy transfer (FRET) is used to detect the denaturation process of double-stranded DNA at nanomolar concentration.
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Affiliation(s)
- A Chen
- School of Engineering, University of California Santa Cruz, Santa Cruz, CA 95064, USA
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Lionnet T, Wu B, Grünwald D, Singer RH, Larson DR. Nuclear physics: quantitative single-cell approaches to nuclear organization and gene expression. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2011; 75:113-26. [PMID: 21502409 PMCID: PMC3145213 DOI: 10.1101/sqb.2010.75.057] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The internal workings of the nucleus remain a mystery. A list of component parts exists, and in many cases their functional roles are known for events such as transcription, RNA processing, or nuclear export. Some of these components exhibit structural features in the nucleus, regions of concentration or bodies that have given rise to the concept of functional compartmentalization--that there are underlying organizational principles to be described. In contrast, a picture is emerging in which transcription appears to drive the assembly of the functional components required for gene expression, drawing from pools of excess factors. Unifying this seemingly dual nature requires a more rigorous approach, one in which components are tracked in time and space and correlated with onset of specific nuclear functions. In this chapter, we anticipate tools that will address these questions and provide the missing kinetics of nuclear function. These tools are based on analyzing the fluctuations inherent in the weak signals of endogenous nuclear processes and determining values for them. In this way, it will be possible eventually to provide a computational model describing the functional relationships of essential components.
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Affiliation(s)
- T Lionnet
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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31
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Schwille P, Ries J. Principles and Applications of Fluorescence Correlation Spectroscopy (FCS). BIOPHOTONICS: SPECTROSCOPY, IMAGING, SENSING, AND MANIPULATION 2011. [DOI: 10.1007/978-90-481-9977-8_4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Photounbinding of calmodulin from a family of CaM binding peptides. PLoS One 2010; 5:e14050. [PMID: 21124984 PMCID: PMC2987815 DOI: 10.1371/journal.pone.0014050] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Accepted: 09/30/2010] [Indexed: 12/29/2022] Open
Abstract
Background Recent studies have shown that fluorescently labeled antibodies can be dissociated from their antigen by illumination with laser light. The mechanism responsible for the photounbinding effect, however, remains elusive. Here, we give important insights into the mechanism of photounbinding and show that the effect is not restricted to antibody/antigen binding. Methodology/Principal Findings We present studies of the photounbinding of labeled calmodulin (CaM) from a set of CaM-binding peptides with different affinities to CaM after one- and two-photon excitation. We found that the photounbinding effect becomes stronger with increasing binding affinity. Our observation that photounbinding can be influenced by using free radical scavengers, that it does not occur with either unlabeled protein or non-fluorescent quencher dyes, and that it becomes evident shortly after or with photobleaching suggest that photounbinding and photobleaching are closely linked. Conclusions/Significance The experimental results exclude surface effects, or heating by laser irradiation as potential causes of photounbinding. Our data suggest that free radicals formed through photobleaching may cause a conformational change of the CaM which lowers their binding affinity with the peptide or its respective binding partner.
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Lobe specific Ca2+-calmodulin nano-domain in neuronal spines: a single molecule level analysis. PLoS Comput Biol 2010; 6:e1000987. [PMID: 21085618 PMCID: PMC2978734 DOI: 10.1371/journal.pcbi.1000987] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2010] [Accepted: 10/04/2010] [Indexed: 01/07/2023] Open
Abstract
Calmodulin (CaM) is a ubiquitous Ca2+ buffer and second messenger that affects cellular function as diverse as cardiac excitability, synaptic plasticity, and gene transcription. In CA1 pyramidal neurons, CaM regulates two opposing Ca2+-dependent processes that underlie memory formation: long-term potentiation (LTP) and long-term depression (LTD). Induction of LTP and LTD require activation of Ca2+-CaM-dependent enzymes: Ca2+/CaM-dependent kinase II (CaMKII) and calcineurin, respectively. Yet, it remains unclear as to how Ca2+ and CaM produce these two opposing effects, LTP and LTD. CaM binds 4 Ca2+ ions: two in its N-terminal lobe and two in its C-terminal lobe. Experimental studies have shown that the N- and C-terminal lobes of CaM have different binding kinetics toward Ca2+ and its downstream targets. This may suggest that each lobe of CaM differentially responds to Ca2+ signal patterns. Here, we use a novel event-driven particle-based Monte Carlo simulation and statistical point pattern analysis to explore the spatial and temporal dynamics of lobe-specific Ca2+-CaM interaction at the single molecule level. We show that the N-lobe of CaM, but not the C-lobe, exhibits a nano-scale domain of activation that is highly sensitive to the location of Ca2+ channels, and to the microscopic injection rate of Ca2+ ions. We also demonstrate that Ca2+ saturation takes place via two different pathways depending on the Ca2+ injection rate, one dominated by the N-terminal lobe, and the other one by the C-terminal lobe. Taken together, these results suggest that the two lobes of CaM function as distinct Ca2+ sensors that can differentially transduce Ca2+ influx to downstream targets. We discuss a possible role of the N-terminal lobe-specific Ca2+-CaM nano-domain in CaMKII activation required for the induction of synaptic plasticity. Calmodulin is a versatile Ca2+ signal mediator and a buffer in a wide variety of body organs including the heart and brain. In the brain, calmodulin regulates intracellular molecular processes that change the strength of connectivity between neurons, thus contributing to various brain functions including memory formation. The exact molecular mechanism as to how calmodulin regulates these processes is not yet known. Interestingly, in other excitable tissues, including the heart, each of two lobes of calmodulin responds differentially toward Ca2+ influx and toward its target molecules (e.g., ion channels). This way, calmodulin precisely controls the Ca2+ dynamics of the cell. We wish to test if a similar mechanism may be operational in neurons so that two lobes of calmodulin interact differentially with Ca2+ ions to activate different downstream molecules that control the strength of connections between neurons. We constructed a detailed simulation of calmodulin that allows us to keep track of its interactions with Ca2+ ions and target proteins at the single molecule level. The simulation predicts that two lobes of calmodulin respond differentially to Ca2+ influx both in space and in time. This work opens a door to future experimental testing of the lobe-specific control of neural function by calmodulin.
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Chudakov DM, Matz MV, Lukyanov S, Lukyanov KA. Fluorescent proteins and their applications in imaging living cells and tissues. Physiol Rev 2010; 90:1103-63. [PMID: 20664080 DOI: 10.1152/physrev.00038.2009] [Citation(s) in RCA: 925] [Impact Index Per Article: 66.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Green fluorescent protein (GFP) from the jellyfish Aequorea victoria and its homologs from diverse marine animals are widely used as universal genetically encoded fluorescent labels. Many laboratories have focused their efforts on identification and development of fluorescent proteins with novel characteristics and enhanced properties, resulting in a powerful toolkit for visualization of structural organization and dynamic processes in living cells and organisms. The diversity of currently available fluorescent proteins covers nearly the entire visible spectrum, providing numerous alternative possibilities for multicolor labeling and studies of protein interactions. Photoactivatable fluorescent proteins enable tracking of photolabeled molecules and cells in space and time and can also be used for super-resolution imaging. Genetically encoded sensors make it possible to monitor the activity of enzymes and the concentrations of various analytes. Fast-maturing fluorescent proteins, cell clocks, and timers further expand the options for real time studies in living tissues. Here we focus on the structure, evolution, and function of GFP-like proteins and their numerous applications for in vivo imaging, with particular attention to recent techniques.
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Loumaigne M, Richard A, Laverdant J, Nutarelli D, Débarre A. Ligand-induced anisotropy of the two-photon luminescence of spherical gold particles in solution unraveled at the single particle level. NANO LETTERS 2010; 10:2817-2824. [PMID: 20593772 DOI: 10.1021/nl100737y] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Here we report on the visible luminescence properties of individual spherical gold particles in solution, obtained by two-photon excited fluorescence correlation spectroscopy and by an original dual Rayleigh-fluorescence method, correlating the Rayleigh scattering and the luminescence fluctuations of the same particle. The results demonstrate that the power needed to observe the two-photon excited visible luminescence depends on the illuminated particle and that the corresponding emission is anisotropic at low power. These observations combined with the evolution of the dynamics of the luminescence with respect to excitation power are interpreted by the presence of unique emissive surface states that are randomly switched off and on by the heat-induced movement of the molecular coating. These characteristics, which remain hidden in macroscopic experiments, have important implications with respect to the potential use of the particles as labels in two-photon imaging in aqueous samples.
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Affiliation(s)
- Matthieu Loumaigne
- Laboratoire Aimé Cotton, CNRS, Université Paris-Sud, Bâtiment 505, 91405 Orsay cedex, France
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Time-resolved luminescence resonance energy transfer imaging of protein-protein interactions in living cells. Proc Natl Acad Sci U S A 2010; 107:13582-7. [PMID: 20643966 DOI: 10.1073/pnas.1002025107] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Förster resonance energy transfer (FRET) with fluorescent proteins permits high spatial resolution imaging of protein-protein interactions in living cells. However, substantial non-FRET fluorescence background can obscure small FRET signals, making many potential interactions unobservable by conventional FRET techniques. Here we demonstrate time-resolved microscopy of luminescence resonance energy transfer (LRET) for live-cell imaging of protein-protein interactions. A luminescent terbium complex, TMP-Lumi4, was introduced into cultured cells using two methods: (i) osmotic lysis of pinocytic vesicles; and (ii) reversible membrane permeabilization with streptolysin O. Upon intracellular delivery, the complex was observed to bind specifically and stably to transgenically expressed Escherichia coli dihydrofolate reductase (eDHFR) fusion proteins. LRET between the eDHFR-bound terbium complex and green fluorescent protein (GFP) was detected as long-lifetime, sensitized GFP emission. Background signals from cellular autofluorescence and directly excited GFP fluorescence were effectively eliminated by imposing a time delay (10 micros) between excitation and detection. Background elimination made it possible to detect interactions between the first PDZ domain of ZO-1 (fused to eDHFR) and the C-terminal YV motif of claudin-1 (fused to GFP) in single microscope images at subsecond time scales. We observed a highly significant (P<10(-6)), six-fold difference between the mean, donor-normalized LRET signal from cells expressing interacting fusion proteins and from control cells expressing noninteracting mutants. The results show that time-resolved LRET microscopy with a selectively targeted, luminescent terbium protein label affords improved speed and sensitivity over conventional FRET methods for a variety of live-cell imaging and screening applications.
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37
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Chen SL, Ling T, Huang SW, Baac HW, Guo LJ. Photoacoustic correlation spectroscopy and its application to low-speed flow measurement. OPTICS LETTERS 2010; 35:1200-2. [PMID: 20410966 PMCID: PMC2859458 DOI: 10.1364/ol.35.001200] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
A photoacoustic correlation technique, inspired by its optical counterpart-the fluorescence correlation spectroscopy (FCS)-was tested for the first time, to our knowledge, to demonstrate the feasibility of low-speed flow measurement based on photoacoustic signal detection. A pulsed laser was used to probe the flow of light-absorbing beads. A photoacoustic correlation system of 0.8 s temporal resolution was built and flow speeds ranging from 249 to 14.9 microm/s with corresponding flow times from 4.42 to 74.1 s were measured. The experiment serves as a proof of concept for photoacoustic correlation spectroscopy, which may have many potential applications similar to the FCS.
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Affiliation(s)
- Sung-Liang Chen
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109
| | - Tao Ling
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109
| | - Sheng-Wen Huang
- Department of Bioengineering, University of Washington, Seattle, WA 98195
| | - Hyoung Won Baac
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109
| | - L. Jay Guo
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109
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38
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Savatier J, Jalaguier S, Ferguson ML, Cavaillès V, Royer CA. Estrogen receptor interactions and dynamics monitored in live cells by fluorescence cross-correlation spectroscopy. Biochemistry 2010; 49:772-81. [PMID: 20039662 DOI: 10.1021/bi9013006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Quantitative characterization of protein interactions in live cells remains one of the most important challenges in modern biology. In the present work we have used two-photon, two-color, fluorescence cross-correlation spectroscopy (FCCS) in transiently transfected COS-7 cells to measure the concentrations and interactions of estrogen receptor (ER) subtypes alpha and beta with one of their transcriptional coactivator proteins, TIF2, as well as heterodimerization between the two ER subtypes. Using this approach in a systematic fashion, we observed a strong ligand-dependent modulation of receptor-coactivator complexation, as well as strong protein concentration dependence for complex formation in the absence of ligand. These quantitative values for protein and complex concentrations provide the first estimates for the ER-TIF2 K(d) for the full-length proteins and in a cellular context (agonist, < approximately 6 nM; antagonist, > approximately 3 microM; unliganded, approximately 200 nM). Coexpression of the two ER subtypes revealed substantial receptor heterodimer formation. They also provide, for the first time, estimated homo- and heterodimerization constants found to be similar and in the low nanomolar range. These results underscore the importance of receptor and coregulator expression levels and stability in the tissue-dependent modulation of receptor function under normal and pathological conditions.
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Affiliation(s)
- Julien Savatier
- Centre de Biochimie Structurale, INSERM U554, and CNRS UMR5048, Université Montpellier 1 and 2, Montpellier F-34090, France
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39
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Lee W, Lee YI, Lee J, Davis LM, Deininger P, Soper SA. Cross-talk-free dual-color fluorescence cross-correlation spectroscopy for the study of enzyme activity. Anal Chem 2010; 82:1401-10. [PMID: 20073480 PMCID: PMC2846527 DOI: 10.1021/ac9024768] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have developed an instrument for spectral cross-talk-free dual-color fluorescence cross-correlation spectroscopy (FCCS), which provides a readout modality for the study of enzyme activity in application areas such as high-throughput screening. Two spectrally distinct (approximately 250 nm) fluorophores, Cy3 and IRD800, were excited simultaneously using two different excitation sources: one poised at 532 nm and the other at 780 nm. The fluorescence information was processed on two different color channels monitored with single-photon avalanche diodes (SPADs) that could transduce events at the single-molecule level. The system provided no color cross-talk (cross-excitation and/or cross-emission) and/or fluorescence resonance energy transfer (FRET), significantly improving data quality. To provide evidence of cross-talk-free operation, the system was evaluated using bright microspheres (lambda(abs) = 532 nm, lambda(em) = 560 nm) and quantum dots (lambda(abs) = 532 nm, lambda(em) = 810 nm). Experimental results indicated that no color leakage from the microspheres or quantum dots into inappropriate color channels was observed. To demonstrate the utility of the system, the enzymatic activity of APE1, which is responsible for nicking the phosphodiester backbone in DNA on the 5' side of an apurinic/apyrimidinic site, was monitored by FCCS using a double-stranded DNA substrate dual labeled with Cy3 and IRD800. Activity of APE1 was also monitored in the presence of an inhibitor (7-nitroindole-2-carboxylic acid) of the enzyme using this cross-talk-free FCCS platform. In all cases, no spectral leakage from single-molecule events into inappropriate color channels was observed.
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Affiliation(s)
- Wonbae Lee
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803-1804, USA
| | - Yong-Ill Lee
- Department of Chemistry, Changwon National University, Changwon, 641-773, South Korea
| | - Jeonghoon Lee
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803-1804, USA
| | - Lloyd M. Davis
- Center for Laser Applications, University of Tennessee Space Institute, Tullahoma, TN 37388, USA
| | - Prescott Deininger
- Tulane University, Department of Epidemiology and Tulane Cancer Center, New Orleans, LA 70112, USA
| | - Steven A. Soper
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803-1804, USA
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40
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Heterospecies partition analysis reveals binding curve and stoichiometry of protein interactions in living cells. Proc Natl Acad Sci U S A 2010; 107:4117-22. [PMID: 20142515 DOI: 10.1073/pnas.0905670107] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Measuring the binding curve and stoichiometry of protein complexes in living cells is a prerequisite for quantitative modeling of cellular processes. Dual-color fluorescence fluctuation spectroscopy provides a general framework for detecting protein interactions, but lacks suitable methods for quantifying protein heterointeractions in the cell. We address this challenge by introducing heterospecies partition (HSP) analysis for protein heterointeractions of the type D + nA<-->DA(n). HSP directly identifies the heterointeracting species from the sample mixture and determines the binding curve and stoichiometry of the protein complex. The HSP method is applied to provide the first direct characterization of the ligand-dependent binding of the retinoic X receptor to the coactivator transcription intermediate factor 2. A previous study based on protein fragments observed a higher binding stoichiometry than biologically expected. We address this difference in stoichiometry by measuring the binding curves of the full-length proteins in living cells. This study provides proof-of-principle experiments that illustrate the potential of HSP as a general and robust analysis tool for the quantitative characterization of protein heterointeractions by dual-color fluorescence fluctuation spectroscopy in living cells.
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41
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Miller AE, Hollars CW, Lane SM, Laurence TA. Fluorescence cross-correlation spectroscopy as a universal method for protein detection with low false positives. Anal Chem 2009; 81:5614-22. [PMID: 19522509 DOI: 10.1021/ac9001645] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Specific, quantitative, and sensitive protein detection with minimal sample preparation is an enduring need in biology and medicine. Protein detection assays ideally provide quick, definitive measurements that use only small amounts of material. Fluorescence cross-correlation spectroscopy (FCCS) has been proposed and developed as a protein detection assay for several years. Here, we combine several recent advances in FCCS apparatus and analysis to demonstrate it as an important method for sensitive, quantitative, information-rich protein detection with low false positives. The addition of alternating laser excitation (ALEX) to FCCS along with a method to exclude signals from occasional aggregates leads to a very low rate of false positives, allowing the detection and quantification of the concentrations of a wide variety of proteins. We detect human chorionic gonadotropin (hCG) using an antibody-based sandwich assay and quantitatively compare our results with calculations based on binding equilibrium equations. Furthermore, using our aggregate exclusion method, we detect smaller oligomers of the prion protein PrP by excluding bright signals from large aggregates.
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Affiliation(s)
- Abigail E Miller
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, USA
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42
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Digman MA, Gratton E. Fluorescence correlation spectroscopy and fluorescence cross-correlation spectroscopy. WILEY INTERDISCIPLINARY REVIEWS. SYSTEMS BIOLOGY AND MEDICINE 2009; 1:273-282. [PMID: 20835996 PMCID: PMC3086279 DOI: 10.1002/wsbm.5] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
This article focuses on methods based on fluctuation correlation spectroscopy to determine the formation of protein complexes in living cells. We present the principles of the fluctuation method applied to cells. We discuss the novelty and the promises of this approach. The emphasis is in the discussion of the underlying statistical assumptions of the image correlation spectroscopy analysis rather than in reviewing applications of the method. Although one example of the application of the fluctuation method is given, this article also contains simulations that are better suited to illustrate and support the basic assumptions of the method.
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Affiliation(s)
- Michelle A. Digman
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, CA 92697, USA
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, CA 92697, USA
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Byrne MJ, Putkey JA, Waxham MN, Kubota Y. Dissecting cooperative calmodulin binding to CaM kinase II: a detailed stochastic model. J Comput Neurosci 2009; 27:621-38. [PMID: 19609660 DOI: 10.1007/s10827-009-0173-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2008] [Revised: 05/28/2009] [Accepted: 07/01/2009] [Indexed: 12/11/2022]
Abstract
Calmodulin (CaM) is a major Ca(2+) binding protein involved in two opposing processes of synaptic plasticity of CA1 pyramidal neurons: long-term potentiation (LTP) and depression (LTD). The N- and C-terminal lobes of CaM bind to its target separately but cooperatively and introduce complex dynamics that cannot be well understood by experimental measurement. Using a detailed stochastic model constructed upon experimental data, we have studied the interaction between CaM and Ca(2+)-CaM-dependent protein kinase II (CaMKII), a key enzyme underlying LTP. The model suggests that the accelerated binding of one lobe of CaM to CaMKII, when the opposing lobe is already bound to CaMKII, is a critical determinant of the cooperative interaction between Ca(2+), CaM, and CaMKII. The model indicates that the target-bound Ca(2+) free N-lobe has an extended lifetime and may regulate the Ca(2+) response of CaMKII during LTP induction. The model also reveals multiple kinetic pathways which have not been previously predicted for CaM-dissociation from CaMKII.
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Affiliation(s)
- Michael J Byrne
- Department of Neurobiology and Anatomy, University of Texas Medical School, Houston, TX 77030, USA
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44
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Fluorescence cross-correlation spectroscopy using single wavelength laser. FRONTIERS OF CHEMISTRY IN CHINA 2009; 4:191-195. [PMID: 32288754 PMCID: PMC7111545 DOI: 10.1007/s11458-009-0036-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In this paper, we first introduced the basic principle of fluorescence cross-correlation spectroscopy (FCCS) and then established an FCCS setup using a single wavelength laser. We systematically optimized the setup, and the detection volume reached about 0.7 fL. The homebuilt setup was successfully applied for the study of the binding reaction of human immunoglobulin G with goat antihuman immunoglobulin G. Using quantum dots (745 nm emission wavelength) and Rhodamine B (580 nm emission wavelength) as labeling probes and 532 nm laser beam as an excitation source, the cross-talk effect was almost completely suppressed. The molecule numbers in a highly focused volume, the concentration, and the diffusion time and hydrodynamic radii of the reaction products can be determined by FCCS system.
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45
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Sanabria H, Swulius MT, Kolodziej SJ, Liu J, Waxham MN. {beta}CaMKII regulates actin assembly and structure. J Biol Chem 2009; 284:9770-80. [PMID: 19208632 DOI: 10.1074/jbc.m809518200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(2+)-Calmodulin-dependent protein kinase II (CaMKII) is an abundant synaptic protein that was recently shown to regulate the organization of actin filaments leading to structural modifications of synapses. CaMKII is a dodecameric complex with a special architecture that provides it with unique potential for organizing the actin cytoskeleton. We report using biochemical assays that the beta isoform of CaMKII binds to and bundles actin filaments, and the disposition of betaCaMKII within the actin bundles was revealed by cryoelectron tomography. In addition, betaCaMKII was found to inhibit actin polymerization, suggesting that it either serves as a capping protein or binds monomeric actin, reducing the amount of freely available monomers to nucleate polymer assembly. By means of fluorescent cross-correlation spectroscopy, we determined that betaCaMKII does indeed bind to monomeric actin, reaching saturation at a stoichiometry of 12:1 actin monomers per betaCaMKII holoenzyme with a binding constant of 2.4 x 10(5) m(-1). In cells, betaCaMKII has a dual functional role; it can sequester monomeric actin to reduce actin polymerization and can also bundle actin filaments. Together, these effects would impact both the dynamics of actin filament assembly and enhance the rigidity of the filaments once formed, significantly impacting the structure of synapses.
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Affiliation(s)
- Hugo Sanabria
- Departments of Neurobiology and Anatomy and Pathology and Laboratory Medicine, University of Texas Health Science Center, Houston, Texas 77030, USA
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46
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Pan W, Filobelo L, Pham NDQ, Galkin O, Uzunova VV, Vekilov PG. Viscoelasticity in homogeneous protein solutions. PHYSICAL REVIEW LETTERS 2009; 102:058101. [PMID: 19257559 DOI: 10.1103/physrevlett.102.058101] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2008] [Indexed: 05/27/2023]
Abstract
We probe the transport properties in protein solutions stable with respect to any, solid or liquid, phase separation as a step in the understanding of transport in the cytosol of live cells. We determine the mean-squared displacement of probe particles in the time range 10;{-3}-10 s in solutions of a model protein. The tested solutions exhibit significant elasticity at high frequencies, while at low frequencies, they are purely viscous. We attribute this viscoelasticity to a dense network of weakly-bound chains of protein molecules with characteristic lifetime of 10-100 ms. The found intrinsic viscoelasticity of protein solutions should be considered in biochemical kinetics models.
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Affiliation(s)
- Weichun Pan
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, USA
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47
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Jung C, Ruthardt N, Lewis R, Michaelis J, Sodeik B, Nolde F, Peneva K, Müllen K, Bräuchle C. Photophysics of New Water-Soluble Terrylenediimide Derivatives and Applications in Biology. Chemphyschem 2009; 10:180-90. [DOI: 10.1002/cphc.200800628] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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48
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Abstract
Imaging membrane dynamics is an important goal, motivated by the abundance of biochemical and biophysical events that are orchestrated at, or by, cellular membranes. The short length scales, fast timescales, and environmental requirements of membrane phenomena present challenges to imaging experiments. Several technical advances offer means to overcome these challenges, and we describe here three powerful techniques applicable to membrane imaging: total internal reflection fluorescence (TIRF) microscopy, fluorescence interference contrast (FLIC) microscopy, and fluorescence correlation spectroscopy (FCS). For each, we discuss the physics underpinning the approach, its practical implementation, and recent examples highlighting its achievements in exploring the membrane environment.
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Affiliation(s)
- Jay T Groves
- Department of Chemistry, University of California, Berkeley, CA 94720, USA.
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49
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Petrášek Z, Schwille P. Fluctuations as a source of information in fluorescence microscopy. J R Soc Interface 2008. [DOI: 10.1098/rsif.2008.0200.focus] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Fluctuations in fluorescence spectroscopy and microscopy have traditionally been regarded as noise—they lower the resolution and contrast and do not permit high acquisition rates. However, fluctuations can also be used to gain additional information about a system. This fact has been exploited in single-point microscopic techniques, such as fluorescence correlation spectroscopy and analysis of single molecule trajectories, and also in the imaging field, e.g. in spatio-temporal image correlation spectroscopy. Here, we discuss how fluctuations are used to obtain more quantitative information from the data than that given by average values, while minimizing the effects of noise due to stochastic photon detection.
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Affiliation(s)
- Zdeněk Petrášek
- Biophysics group, Biotechnologisches Zentrum, Technische Universität DresdenTatzberg 47-51, 01307 Dresden, Germany
| | - Petra Schwille
- Biophysics group, Biotechnologisches Zentrum, Technische Universität DresdenTatzberg 47-51, 01307 Dresden, Germany
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50
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Abstract
Calmodulin (CaM) is the major pathway that transduces intracellular Ca2+ increases to the activation of a wide variety of downstream signaling enzymes. CaM and its target proteins form an integrated signaling network believed to be tuned spatially and temporally to control CaM's ability to appropriately pass signaling events downstream. Here, we report the spatial diffusivity and availability of CaM labeled with enhanced green fluorescent protein (eGFP)-CaM, at basal and elevated Ca2+,quantified by the novel fluorescent techniques of raster image scanning spectroscopy and number and brightness analysis. Our results show that in basal Ca2+ conditions cytoplasmic eGFP-CaM diffuses at a rate of 10 microm(2)/s, twofold slower than the noninteracting tracer, eGFP, indicating that a significant fraction of CaM is diffusing bound to other partners. The diffusion rate of eGFP-CaM is reduced to 7 microm(2)/s when a large (646 kDa) target protein Ca2+/CaM-dependent protein kinase II is coexpressed in the cells. In addition, the presence of Ca2+/calmodulin-dependent protein kinase II, which can bind up to 12 CaM molecules per holoenzyme, increases the stoichiometry of binding to an average of 3 CaMs per diffusive molecule. Elevating intracellular Ca2+ did not have a major impact on the diffusion of CaM complexes. These results present us with a model whereby CaM is spatially modulated by target proteins and support the hypothesis that CaM availability is a limiting factor in the network of CaM-signaling enzymes.
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