1
|
Zulueta Díaz YDLM, Kure JL, Grosso RA, Andersen C, Pandzic E, Sengupta P, Wiseman PW, Arnspang EC. Quantitative image mean squared displacement (iMSD) analysis of the dynamics of Aquaporin 2 within the membrane of live cells. Biochim Biophys Acta Gen Subj 2023; 1867:130449. [PMID: 37748662 DOI: 10.1016/j.bbagen.2023.130449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 08/22/2023] [Accepted: 08/25/2023] [Indexed: 09/27/2023]
Abstract
Nanodomains are a biological membrane phenomenon which have a large impact on various cellular processes. They are often analysed by looking at the lateral dynamics of membrane lipids or proteins. The localization of the plasma membrane protein aquaporin-2 in nanodomains has so far been unknown. In this study, we use total internal reflection fluorescence microscopy to image Madin-Darby Canine Kidney (MDCK) cells expressing aquaporin-2 tagged with mEos 3.2. Then, image mean squared displacement (iMSD) approach was used to analyse the diffusion of aquaporin-2, revealing that aquaporin-2 is confined within membrane nanodomains. Using iMSD analysis, we found that the addition of the drug forskolin increases the diffusion of aquaporin-2 within the confined domains, which is in line with previous studies. Finally, we observed an increase in the size of the membrane domains and the extent of trapping of aquaporin-2 after stimulation with forskolin.
Collapse
Affiliation(s)
| | - Jakob Lavrsen Kure
- Department of Green Technology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Rubén Adrián Grosso
- Department of Green Technology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Camilla Andersen
- Department of Green Technology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Elvis Pandzic
- Mark Wainwright Analytical Centre, Lowy Cancer Research Centre C25, University of New South Wales, NSW, 2052, Australia
| | - Prabuddha Sengupta
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, USA; Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Paul W Wiseman
- Department of Chemistry, McGill University, Montreal, Québec, Canada; Department of Physics, McGill University, Montreal, Québec, Canada
| | - Eva C Arnspang
- Department of Green Technology, University of Southern Denmark, 5230 Odense M, Denmark; The Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, USA.
| |
Collapse
|
2
|
Bendixen KK, Mindegaard M, Epistolio S, Dazio G, Marchi F, Spina P, Arnspang EC, Soerensen M, Christensen UB, Frattini M, Petersen RK. A qPCR technology for direct quantification of methylation in untreated DNA. Nat Commun 2023; 14:5153. [PMID: 37620381 PMCID: PMC10449789 DOI: 10.1038/s41467-023-40873-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 08/14/2023] [Indexed: 08/26/2023] Open
Abstract
DNA methylation is important for gene expression and alterations in DNA methylation are involved in the development and progression of cancer and other major diseases. Analysis of DNA methylation patterns has until now been dependent on either a chemical or an enzymatic pre-treatment, which are both time consuming procedures and potentially biased due to incomplete treatment. We present a qPCR technology, EpiDirect®, that allows for direct PCR quantification of DNA methylations using untreated DNA. EpiDirect® is based on the ability of Intercalating Nucleic Acids (INA®) to differentiate between methylated and unmethylated cytosines in a special primer design. With this technology, we develop an assay to analyze the methylation status of a region of the MGMT promoter used in treatment selection and prognosis of glioblastoma patients. We compare the assay to two bisulfite-relying, methyl-specific PCR assays in a study involving 42 brain tumor FFPE samples, revealing high sensitivity, specificity, and the clinical utility of the method.
Collapse
Affiliation(s)
- Kamilla Kolding Bendixen
- PentaBase A/S, Odense, Denmark.
- Epidemiology, Biostatistics and Biodemography, Department of Public Health, University of Southern Denmark, Odense, Denmark.
| | | | - Samantha Epistolio
- Laboratory of Molecular Pathology, Institute of Pathology, Ente Ospedaliero Cantonale (EOC), Locarno, Switzerland
| | - Giulia Dazio
- Laboratory of Molecular Pathology, Institute of Pathology, Ente Ospedaliero Cantonale (EOC), Locarno, Switzerland
| | - Francesco Marchi
- Service of Neurosurgery, Neurocenter of the Southern Switzerland, Regional Hospital of Lugano, Lugano, Switzerland
| | - Paolo Spina
- Laboratory of Molecular Pathology, Institute of Pathology, Ente Ospedaliero Cantonale (EOC), Locarno, Switzerland
- Department of Health Sciences, University of Eastern Piedmont, Novara, Italy
| | - Eva C Arnspang
- Department of Green Technology, University of Southern Denmark, Odense, Denmark
| | - Mette Soerensen
- Epidemiology, Biostatistics and Biodemography, Department of Public Health, University of Southern Denmark, Odense, Denmark
| | | | - Milo Frattini
- Laboratory of Molecular Pathology, Institute of Pathology, Ente Ospedaliero Cantonale (EOC), Locarno, Switzerland
| | | |
Collapse
|
3
|
Andersen CB, Lausdahl AK, Nielsen J, Clausen MP, Mulder FAA, Otzen DE, Arnspang EC. 4-Oxo-2-nonenal-Induced α-Synuclein Oligomers Interact with Membranes in the Cell, Leading to Mitochondrial Fragmentation. Biochemistry 2023; 62:2417-2425. [PMID: 37487228 DOI: 10.1021/acs.biochem.3c00114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/26/2023]
Abstract
Oxidative stress and formation of cytotoxic oligomers by the natively unfolded protein α-synuclein (α-syn) are both connected to the development of Parkinson's disease. This effect has been linked to lipid peroxidation and membrane disruption, but the specific mechanisms behind these phenomena remain unclear. To address this, we have prepared α-syn oligomers (αSOs) in vitro in the presence of the lipid peroxidation product 4-oxo-2-nonenal and investigated their interaction with live cells using in-cell NMR as well as stimulated emission depletion (STED) super-resolution and confocal microscopy. We find that the αSOs interact strongly with organellar components, leading to strong immobilization of the protein's otherwise flexible C-terminus. STED microscopy reveals that the oligomers localize to small circular structures inside the cell, while confocal microscopy shows mitochondrial fragmentation and association with both late endosome and retromer complex before the SOs interact with mitochondria. Our study provides direct evidence for close contact between cytotoxic α-syn aggregates and membraneous compartments in the cell.
Collapse
Affiliation(s)
- Camilla B Andersen
- Interdisciplinary Nanoscience Center (iNANO), Gustav Wieds Vej 14, Aarhus University, 8000 Aarhus C, Denmark
- Department of Green Technology, SDU-Biotechnology, University of Southern Denmark, 5230 Odense, Denmark
| | - Astrid K Lausdahl
- Department of Green Technology, SDU-Biotechnology, University of Southern Denmark, 5230 Odense, Denmark
| | - Janni Nielsen
- Interdisciplinary Nanoscience Center (iNANO), Gustav Wieds Vej 14, Aarhus University, 8000 Aarhus C, Denmark
| | - Mathias P Clausen
- Department of Green Technology, SDU-Biotechnology, University of Southern Denmark, 5230 Odense, Denmark
| | - Frans A A Mulder
- Interdisciplinary Nanoscience Center (iNANO), Gustav Wieds Vej 14, Aarhus University, 8000 Aarhus C, Denmark
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark
| | - Daniel E Otzen
- Interdisciplinary Nanoscience Center (iNANO), Gustav Wieds Vej 14, Aarhus University, 8000 Aarhus C, Denmark
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark
| | - Eva C Arnspang
- Department of Green Technology, SDU-Biotechnology, University of Southern Denmark, 5230 Odense, Denmark
| |
Collapse
|
4
|
Hundahl AC, Weller A, Larsen JB, Hjørringgaard CU, Hansen MB, Mündler AK, Knuhtsen A, Kristensen K, Arnspang EC, Andresen TL, Mortensen KI, Marie R. Quantitative live-cell imaging of lipidated peptide transport through an epithelial cell layer. J Control Release 2023; 355:122-134. [PMID: 36724849 DOI: 10.1016/j.jconrel.2023.01.066] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 01/10/2023] [Accepted: 01/26/2023] [Indexed: 02/03/2023]
Abstract
Oral drug delivery increases patient compliance and is thus the preferred administration route for most drugs. However, for biologics the intestinal barrier greatly limits the absorption and reduces their bioavailability. One strategy employed to improve on this is chemical modification of the biologic through the addition of lipid side chains. While it has been established that lipidation of peptides can increase transport, a mechanistic understanding of this effect remains largely unexplored. To pursue this mechanistic understanding, end-point detection of biopharmaceuticals transported through a monolayer of fully polarized epithelial cells is typically used. However, these methods are time-consuming and tedious. Furthermore, most established methods cannot be combined easily with high-resolution live-cell fluorescence imaging that could provide a mechanistic insight into cellular uptake and transport. Here we address this challenge by developing an axial PSF deconvolution scheme to quantify the transport of peptides through a monolayer of Caco-2 cells using single-cell analysis with live-cell confocal fluorescence microscopy. We then measure the known cross-barrier transport of several compounds in our model and compare the results with results obtained in an established microfluidic model finding similar transport phenotypes. This verifies that already after two days the Caco-2 cells in our model form a tight monolayer and constitute a functional barrier model. We then apply this assay to investigate the effects of side chain lipidation of the model peptide drug salmon calcitonin (sCT) modified with 4‑carbon and 8‑carbon-long fatty acid chains. Furthermore, we compare that with experiments performed at lower temperature and using inhibitors for some endocytotic pathways to pinpoint how lipidation length modifies the main avenues for the transport. We thus show that increasing the length of the lipid chain increases the transport of the drug significantly but also makes endocytosis the primary transport mechanism in a short-term cell culture model.
Collapse
Affiliation(s)
- Adam Coln Hundahl
- Technical University of Denmark, Department of Health Technology, Ørsteds Plads, Building 345C, DK-2800 Kgs. Lyngby, Denmark
| | - Arjen Weller
- Technical University of Denmark, Department of Health Technology, Ørsteds Plads, Building 345C, DK-2800 Kgs. Lyngby, Denmark
| | - Jannik Bruun Larsen
- Technical University of Denmark, Department of Health Technology, Ørsteds Plads, Building 345C, DK-2800 Kgs. Lyngby, Denmark
| | - Claudia U Hjørringgaard
- Technical University of Denmark, Department of Health Technology, Ørsteds Plads, Building 345C, DK-2800 Kgs. Lyngby, Denmark
| | - Morten B Hansen
- Technical University of Denmark, Department of Health Technology, Ørsteds Plads, Building 345C, DK-2800 Kgs. Lyngby, Denmark
| | - Ann-Kathrin Mündler
- Technical University of Denmark, Department of Health Technology, Ørsteds Plads, Building 345C, DK-2800 Kgs. Lyngby, Denmark
| | - Astrid Knuhtsen
- Technical University of Denmark, Department of Health Technology, Ørsteds Plads, Building 345C, DK-2800 Kgs. Lyngby, Denmark
| | - Kasper Kristensen
- Technical University of Denmark, Department of Health Technology, Ørsteds Plads, Building 345C, DK-2800 Kgs. Lyngby, Denmark
| | - Eva C Arnspang
- Technical University of Denmark, Department of Health Technology, Ørsteds Plads, Building 345C, DK-2800 Kgs. Lyngby, Denmark
| | - Thomas Lars Andresen
- Technical University of Denmark, Department of Health Technology, Ørsteds Plads, Building 345C, DK-2800 Kgs. Lyngby, Denmark
| | - Kim I Mortensen
- Technical University of Denmark, Department of Health Technology, Ørsteds Plads, Building 345C, DK-2800 Kgs. Lyngby, Denmark
| | - Rodolphe Marie
- Technical University of Denmark, Department of Health Technology, Ørsteds Plads, Building 345C, DK-2800 Kgs. Lyngby, Denmark.
| |
Collapse
|
5
|
Andersen C, Zulueta Díaz YDLM, Kure JL, Hessellund Eriksen M, Lovatt AL, Lagerholm C, Morales S, Sehayek S, Sheard TMD, Wiseman PW, Arnspang EC. Angiotensin II Treatment Induces Reorganization and Changes in the Lateral Dynamics of Angiotensin II Type 1 Receptor in the Plasma Membrane Elucidated by Photoactivated Localization Microscopy Combined with Image Spatial Correlation Analysis. Anal Chem 2023; 95:730-738. [PMID: 36574961 DOI: 10.1021/acs.analchem.2c02720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The mechanisms by which angiotensin II type 1 receptor is distributed and the diffusional pattern in the plasma membrane (PM) remain unclear, despite their crucial role in cardiovascular homeostasis. In this work, we obtained quantitative information of angiotensin II type 1 receptor (AT1R) lateral dynamics as well as changes in the diffusion properties after stimulation with ligands in living cells using photoactivated localization microscopy (PALM) combined with image spatial-temporal correlation analysis. To study the organization of the receptor at the nanoscale, expansion microscopy (ExM) combined with PALM was performed. This study revealed that AT1R lateral diffusion increased after binding to angiotensin II (Ang II) and the receptor diffusion was transiently confined in the PM. In addition, ExM revealed that AT1R formed nanoclusters at the PM and the cluster size significantly decreased after Ang II treatment. Taking these results together suggest that Ang II binding and activation cause reorganization and changes in the dynamics of AT1R at the PM.
Collapse
Affiliation(s)
- Camilla Andersen
- SDU Biotechnology, Department of Green Technology, University of Southern Denmark, Odense M5230, Denmark
| | | | - Jakob L Kure
- SDU Biotechnology, Department of Green Technology, University of Southern Denmark, Odense M5230, Denmark
| | - Mathias Hessellund Eriksen
- SDU Biotechnology, Department of Green Technology, University of Southern Denmark, Odense M5230, Denmark
| | - Adam Leslie Lovatt
- SDU Biotechnology, Department of Green Technology, University of Southern Denmark, Odense M5230, Denmark
| | | | - Sebastian Morales
- Department of Physics and Department of Chemistry, McGill University, MontrealH3A 0B8, Canada
| | - Simon Sehayek
- Department of Physics and Department of Chemistry, McGill University, MontrealH3A 0B8, Canada
| | - Thomas M D Sheard
- School of Biosciences, University of Sheffield, SheffieldS10 2TN, U.K
| | - Paul W Wiseman
- Department of Physics and Department of Chemistry, McGill University, MontrealH3A 0B8, Canada
| | - Eva C Arnspang
- SDU Biotechnology, Department of Green Technology, University of Southern Denmark, Odense M5230, Denmark
| |
Collapse
|
6
|
Notabi MK, Arnspang EC, Andersen MØ. Antibody conjugated lipid nanoparticles as a targeted drug delivery system for hydrophobic pharmaceuticals. Eur J Pharm Sci 2021; 161:105777. [PMID: 33647401 DOI: 10.1016/j.ejps.2021.105777] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 02/10/2021] [Accepted: 02/23/2021] [Indexed: 12/12/2022]
Abstract
Cancer remains a significant health issue worldwide. The most common group of chemotherapeutic agents are small-molecule drugs, which often are associated with toxic side-effects and non-specific delivery, leading to limited therapeutic effect. This paper describes the development of a targeted drug delivery system based on lipid nanoparticles for cancer therapy. The lipid nanoparticles consist of a lipid core conjugated to an albumin stealth coating and targeting antibodies through thiol chemistry synthesized utilizing a one-step method. Applying the developed method, lipid nanoparticles with diameters down to 87 nm, capable of encapsulating small molecule compounds were synthesized. Cellular uptake studies of the lipid nanoparticles loaded with the model drug Nile red demonstrated that stealth-coating reduced non-specific cell uptake by up to a 1000-fold compared to free drug. Moreover, antibody-conjugation led to a significant cellular retargeting. Finally, it was shown that the lipid nanoparticles undergo cellular uptake through the endocytic pathway. The lipid nanoparticles are simple to synthesize, stabile in serum and have the potential to be versatile targeted towards receptors selectively expressed by diseased cells using antibodies. Thus, the system may reduce the toxic side-effects of cancer drugs while improving their delivery to cancer cells, increasing the therapeutic effect.
Collapse
Affiliation(s)
- Martine K Notabi
- SDU Biotechnology, Department of Green Technology, Faculty of Engineering, University of Southern Denmark, Campusvej 55, Odense M DK-5230, Denmark
| | - Eva C Arnspang
- SDU Biotechnology, Department of Green Technology, Faculty of Engineering, University of Southern Denmark, Campusvej 55, Odense M DK-5230, Denmark
| | - Morten Ø Andersen
- SDU Biotechnology, Department of Green Technology, Faculty of Engineering, University of Southern Denmark, Campusvej 55, Odense M DK-5230, Denmark.
| |
Collapse
|
7
|
Arnspang EC, Sengupta P, Mortensen KI, Jensen HH, Hahn U, Jensen EBV, Lippincott-Schwartz J, Nejsum LN. Regulation of Plasma Membrane Nanodomains of the Water Channel Aquaporin-3 Revealed by Fixed and Live Photoactivated Localization Microscopy. Nano Lett 2019; 19:699-707. [PMID: 30584808 DOI: 10.1021/acs.nanolett.8b03721] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Several aquaporin (AQP) water channels are short-term regulated by the messenger cyclic adenosine monophosphate (cAMP), including AQP3. Bulk measurements show that cAMP can change diffusive properties of AQP3; however, it remains unknown how elevated cAMP affects AQP3 organization at the nanoscale. Here we analyzed AQP3 nano-organization following cAMP stimulation using photoactivated localization microscopy (PALM) of fixed cells combined with pair correlation analysis. Moreover, in live cells, we combined PALM acquisitions of single fluorophores with single-particle tracking (spt-PALM). These analyses revealed that AQP3 tends to cluster and that the diffusive mobility is confined to nanodomains with radii of ∼150 nm. This domain size increases by ∼30% upon elevation of cAMP, which, however, is not accompanied by a significant increase in the confined diffusion coefficient. This regulation of AQP3 organization at the nanoscale may be important for understanding the mechanisms of water AQP3-mediated water transport across plasma membranes.
Collapse
Affiliation(s)
- Eva C Arnspang
- Department of Clinical Medicine , Aarhus University Aarhus DK-8000 , Denmark
- Interdisciplinary Nanoscience Center (iNANO) , Aarhus University , Aarhus DK-8000 , Denmark
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development , National Institutes of Health , Bethesda , Maryland 20892 , United States
- Department of Chemical Engineering, Biotechnology and Environmental Technology , University of Southern Denmark , Odense M DK-5230 , Denmark
| | - Prabuddha Sengupta
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development , National Institutes of Health , Bethesda , Maryland 20892 , United States
- Janelia Research Campus , Ashburn , Virginia 20147 , United States
| | - Kim I Mortensen
- Department of Micro- and Nanotechnology , Technical University of Denmark , Kongens Lyngby DK-2800 , Denmark
| | - Helene H Jensen
- Department of Clinical Medicine , Aarhus University Aarhus DK-8000 , Denmark
- Department of Molecular Biology and Genetics , Aarhus University , Aarhus DK-8000 , Denmark
| | - Ute Hahn
- Department of Mathematics , Aarhus University , Aarhus DK-8000 , Denmark
| | - Eva B V Jensen
- Department of Mathematics , Aarhus University , Aarhus DK-8000 , Denmark
| | - Jennifer Lippincott-Schwartz
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development , National Institutes of Health , Bethesda , Maryland 20892 , United States
- Janelia Research Campus , Ashburn , Virginia 20147 , United States
| | - Lene N Nejsum
- Department of Clinical Medicine , Aarhus University Aarhus DK-8000 , Denmark
- Interdisciplinary Nanoscience Center (iNANO) , Aarhus University , Aarhus DK-8000 , Denmark
| |
Collapse
|
8
|
Pipó-Ollé E, Walke P, Notabi MK, El-Houri RB, Østergaard Andersen M, Needham D, Arnspang EC. Uptake of New Lipid-coated Nanoparticles Containing Falcarindiol by Human Mesenchymal Stem Cells. J Vis Exp 2019. [DOI: 10.3791/59094] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
|
9
|
Arnspang EC, Login FH, Koffman JS, Sengupta P, Nejsum LN. AQP2 Plasma Membrane Diffusion Is Altered by the Degree of AQP2-S256 Phosphorylation. Int J Mol Sci 2016; 17:ijms17111804. [PMID: 27801846 PMCID: PMC5133805 DOI: 10.3390/ijms17111804] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 09/15/2016] [Accepted: 09/22/2016] [Indexed: 01/21/2023] Open
Abstract
Fine tuning of urine concentration occurs in the renal collecting duct in response to circulating levels of arginine vasopressin (AVP). AVP stimulates intracellular cAMP production, which mediates exocytosis of sub-apical vesicles containing the water channel aquaporin-2 (AQP2). Protein Kinase A (PKA) phosphorylates AQP2 on serine-256 (S256), which triggers plasma membrane accumulation of AQP2. This mediates insertion of AQP2 into the apical plasma membrane, increasing water permeability of the collecting duct. AQP2 is a homo-tetramer. When S256 on all four monomers is changed to the phosphomimic aspartic acid (S256D), AQP2-S256D localizes to the plasma membrane and internalization is decreased. In contrast, when S256 is mutated to alanine (S256A) to mimic non-phosphorylated AQP2, AQP2-S256A localizes to intracellular vesicles as well as the plasma membrane, with increased internalization from the plasma membrane. S256 phosphorylation is not necessary for exocytosis and dephosphorylation is not necessary for endocytosis, however, the degree of S256 phosphorylation is hypothesized to regulate the kinetics of AQP2 endocytosis and thus, retention time in the plasma membrane. Using k-space Image Correlation Spectroscopy (kICS), we determined how the number of phosphorylated to non-phosphorylated S256 monomers in the AQP2 tetramer affects diffusion speed of AQP2 in the plasma membrane. When all four monomers mimicked constitutive phosphorylation (AQP2-S256D), diffusion was faster than when all four were non-phosphorylated (AQP2-S256A). AQP2-WT diffused at a speed similar to that of AQP2-S256D. When an average of two or three monomers in the tetramer were constitutively phosphorylated, the average diffusion coefficients were not significantly different to that of AQP2-S256D. However, when only one monomer was phosphorylated, diffusion was slower and similar to AQP2-S256A. Thus, AQP2 with two to four phosphorylated monomers has faster plasma membrane kinetics, than the tetramer which contains just one or no phosphorylated monomers. This difference in diffusion rate may reflect behavior of AQP2 tetramers destined for either plasma membrane retention or endocytosis.
Collapse
Affiliation(s)
- Eva C Arnspang
- Department of Clinical Medicine, Aarhus University, DK-8000 Aarhus C, Denmark.
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Frédéric H Login
- Department of Clinical Medicine, Aarhus University, DK-8000 Aarhus C, Denmark.
| | - Jennifer S Koffman
- Department of Interdisciplinary Nanoscience Center, Aarhus University, DK-8000 Aarhus C, Denmark.
| | - Prabuddha Sengupta
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Lene N Nejsum
- Department of Clinical Medicine, Aarhus University, DK-8000 Aarhus C, Denmark.
| |
Collapse
|
10
|
Koffman JS, Arnspang EC, Marlar S, Nejsum LN. Opposing Effects of cAMP and T259 Phosphorylation on Plasma Membrane Diffusion of the Water Channel Aquaporin-5 in Madin-Darby Canine Kidney Cells. PLoS One 2015. [PMID: 26218429 PMCID: PMC4517861 DOI: 10.1371/journal.pone.0133324] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Aquaporin-5 (AQP5) facilitates passive water transport in glandular epithelia in response to secretory stimuli via intracellular pathways involving calcium release, cAMP and protein kinase A (PKA). In epithelial plasma membranes, AQP5 may be acutely regulated to facilitate water transport in response to physiological stimuli by changes in protein modifications, interactions with proteins and lipids, nanoscale membrane domain organization, and turnover rates. Such regulatory mechanisms could potentially be associated with alteration of diffusion behavior, possibly resulting in a change in the plasma membrane diffusion coefficient of AQP5. We aimed to test the short-term regulatory effects of the above pathways, by measuring lateral diffusion of AQP5 and an AQP5 phospho-mutant, T259A, using k-space Image Correlation Spectroscopy of quantum dot- and EGFP-labeled AQP5. Elevated cAMP and PKA inhibition significantly decreased lateral diffusion of AQP5, whereas T259A mutation showed opposing effects; slowing diffusion without stimulation and increasing diffusion to basal levels after cAMP elevation. Thus, lateral diffusion of AQP5 is significantly regulated by cAMP, PKA, and T259 phosphorylation, which could be important for regulating water flow in glandular secretions.
Collapse
Affiliation(s)
- Jennifer S. Koffman
- Department of Molecular Biology and Genetics and Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, Denmark
| | - Eva C. Arnspang
- Department of Molecular Biology and Genetics and Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, Denmark
| | - Saw Marlar
- Department of Molecular Biology and Genetics and Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, Denmark
| | - Lene N. Nejsum
- Department of Molecular Biology and Genetics and Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, Denmark
- * E-mail:
| |
Collapse
|
11
|
Almeida R, Berzina Z, Arnspang EC, Baumgart J, Vogt J, Nitsch R, Ejsing CS. Quantitative spatial analysis of the mouse brain lipidome by pressurized liquid extraction surface analysis. Anal Chem 2015; 87:1749-56. [PMID: 25548943 DOI: 10.1021/ac503627z] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Here we describe a novel surface sampling technique termed pressurized liquid extraction surface analysis (PLESA), which in combination with a dedicated high-resolution shotgun lipidomics routine enables both quantification and in-depth structural characterization of molecular lipid species extracted directly from tissue sections. PLESA uses a sealed and pressurized sampling probe that enables the use of chloroform-containing extraction solvents for efficient in situ lipid microextraction with a spatial resolution of 400 μm. Quantification of lipid species is achieved by the inclusion of internal lipid standards in the extraction solvent. The analysis of lipid microextracts by nanoelectrospray ionization provides long-lasting ion spray which in conjunction with a hybrid ion trap-orbitrap mass spectrometer enables identification and quantification of molecular lipid species using a method with successive polarity shifting, high-resolution Fourier transform mass spectrometry (FTMS), and fragmentation analysis. We benchmarked the performance of the PLESA approach for in-depth lipidome analysis by comparing it to conventional lipid extraction of excised tissue homogenates and by mapping the spatial distribution and molar abundance of 170 molecular lipid species across different anatomical mouse brain regions.
Collapse
Affiliation(s)
- Reinaldo Almeida
- VILLUM Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark , Odense, Denmark
| | | | | | | | | | | | | |
Collapse
|
12
|
Marlar S, Arnspang EC, Pedersen GA, Koffman JS, Nejsum LN. Measuring localization and diffusion coefficients of basolateral proteins in lateral versus basal membranes using functionalized substrates and kICS analysis. Biochimica et Biophysica Acta (BBA) - Biomembranes 2014; 1838:2404-11. [DOI: 10.1016/j.bbamem.2014.06.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 06/03/2014] [Accepted: 06/09/2014] [Indexed: 11/17/2022]
|
13
|
Jauffred L, Kyrsting A, Arnspang EC, Reihani SNS, Oddershede LB. Sub-diffraction positioning of a two-photon excited and optically trapped quantum dot. Nanoscale 2014; 6:6997-7003. [PMID: 24839080 DOI: 10.1039/c4nr01319k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Colloidal quantum dots are luminescent long-lived probes that can be two-photon excited and manipulated by a single laser beam. Therefore, quantum dots can be used for simultaneous single molecule visualization and force manipulation using an infra-red laser. Here, we show that even a single optically trapped quantum dot, performing restricted Brownian motion within the focal volume, can be two-photon excited by the trapping laser beam and its luminescence can be detected by a camera. After two-photon excitation for a time long enough, the emitted light from the quantum dot is shown to blueshift. A quantum dot is much smaller than a diffraction limited laser focus and by mapping out the intensity of the focal volume and overlaying this with the positions visited by a quantum dot, a quantum dot is shown often to explore regions of the focal volume where the intensity is too low to render two-photon absorption likely. This is in accordance with the observation that a trapped quantum dot is only fluorescing 5-10 percent of the time. The results are important for realizing nano-scale quantum dot control and visualization and for correct interpretation of experiments using two-photon excited quantum dots as markers.
Collapse
|
14
|
Clausen MP, Arnspang EC, Ballou B, Bear JE, Lagerholm BC. Simultaneous multi-species tracking in live cells with quantum dot conjugates. PLoS One 2014; 9:e97671. [PMID: 24892555 PMCID: PMC4043679 DOI: 10.1371/journal.pone.0097671] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2012] [Accepted: 04/23/2014] [Indexed: 11/18/2022] Open
Abstract
Quantum dots are available in a range of spectrally separated emission colors and with a range of water-stabilizing surface coatings that offers great flexibility for enabling bio-specificity. In this study, we have taken advantage of this flexibility to demonstrate that it is possible to perform a simultaneous investigation of the lateral dynamics in the plasma membrane of i) the transmembrane epidermal growth factor receptor, ii) the glucosylphospatidylinositol-anchored protein CD59, and iii) ganglioside GM1-cholera toxin subunit B clusters in a single cell. We show that a large number of the trajectories are longer than 50 steps, which we by simulations show to be sufficient for robust single trajectory analysis. This analysis shows that the populations of the diffusion coefficients are heterogeneously distributed for all three species, but differ between the different species. We further show that the heterogeneity is decreased upon treating the cells with methyl-β-cyclodextrin.
Collapse
Affiliation(s)
- Mathias P. Clausen
- MEMPHYS – Center for Biomembrane Physics and Danish Molecular Biomedical Imaging Center (DaMBIC), University of Southern Denmark, Odense M, Denmark
| | - Eva C. Arnspang
- MEMPHYS – Center for Biomembrane Physics and Danish Molecular Biomedical Imaging Center (DaMBIC), University of Southern Denmark, Odense M, Denmark
| | - Byron Ballou
- Molecular Biosensor and Imaging Center (MBIC), Mellon Institute, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
| | - James E. Bear
- Lineberger Comprehensive Cancer Center and Department of Cell and Developmental Biology, Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - B. Christoffer Lagerholm
- MEMPHYS – Center for Biomembrane Physics and Danish Molecular Biomedical Imaging Center (DaMBIC), University of Southern Denmark, Odense M, Denmark
- * E-mail:
| |
Collapse
|
15
|
Arnspang EC, Koffman JS, Marlar S, Wiseman PW, Nejsum LN. Easy measurement of diffusion coefficients of EGFP-tagged plasma membrane proteins using k-Space Image Correlation Spectroscopy. J Vis Exp 2014. [PMID: 24893770 DOI: 10.3791/51074] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Lateral diffusion and compartmentalization of plasma membrane proteins are tightly regulated in cells and thus, studying these processes will reveal new insights to plasma membrane protein function and regulation. Recently, k-Space Image Correlation Spectroscopy (kICS)(1) was developed to enable routine measurements of diffusion coefficients directly from images of fluorescently tagged plasma membrane proteins, that avoided systematic biases introduced by probe photophysics. Although the theoretical basis for the analysis is complex, the method can be implemented by nonexperts using a freely available code to measure diffusion coefficients of proteins. kICS calculates a time correlation function from a fluorescence microscopy image stack after Fourier transformation of each image to reciprocal (k-) space. Subsequently, circular averaging, natural logarithm transform and linear fits to the correlation function yields the diffusion coefficient. This paper provides a step-by-step guide to the image analysis and measurement of diffusion coefficients via kICS. First, a high frame rate image sequence of a fluorescently labeled plasma membrane protein is acquired using a fluorescence microscope. Then, a region of interest (ROI) avoiding intracellular organelles, moving vesicles or protruding membrane regions is selected. The ROI stack is imported into a freely available code and several defined parameters (see Method section) are set for kICS analysis. The program then generates a "slope of slopes" plot from the k-space time correlation functions, and the diffusion coefficient is calculated from the slope of the plot. Below is a step-by-step kICS procedure to measure the diffusion coefficient of a membrane protein using the renal water channel aquaporin-3 tagged with EGFP as a canonical example.
Collapse
Affiliation(s)
- Eva C Arnspang
- Institute of Molecular Biology and Genetics and Interdisciplinary Nanoscience Center, Aarhus University;
| | - Jennifer S Koffman
- Institute of Molecular Biology and Genetics and Interdisciplinary Nanoscience Center, Aarhus University
| | - Saw Marlar
- Institute of Molecular Biology and Genetics and Interdisciplinary Nanoscience Center, Aarhus University
| | | | - Lene N Nejsum
- Institute of Molecular Biology and Genetics and Interdisciplinary Nanoscience Center, Aarhus University;
| |
Collapse
|
16
|
Marlar S, Arnspang EC, Koffman JS, Løcke EM, Christensen BM, Nejsum LN. Elevated cAMP increases aquaporin-3 plasma membrane diffusion. Am J Physiol Cell Physiol 2014; 306:C598-606. [PMID: 24452376 DOI: 10.1152/ajpcell.00132.2013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Regulated urine concentration takes place in the renal collecting duct upon arginine vasopressin (AVP) stimulation, where subapical vesicles containing aquaporin-2 (AQP2) are inserted into the apical membrane instantly increasing water reabsorption and urine concentration. The reabsorped water exits via basolateral AQP3 and AQP4. Upon long-term stimulation with AVP or during thirst, expression levels of both AQP2 and AQP3 are increased; however, there is so far no evidence for short-term AVP regulation of AQP3 or AQP4. To facilitate the increase in transepithelial water transport, AQP3 may be short-term regulated via changes in protein-protein interactions, incorporation into lipid rafts, and/or changes in steady-state turnover, which could result in changes in the diffusion behavior of AQP3. Thus we measured AQP3 diffusion coefficients upon stimulation with the AVP mimic forskolin to reveal if AQP3 could be short-term regulated by AVP. k-Space image correlation spectroscopy (kICS) analysis of time-lapse image sequences of basolateral enhanced green fluorescent protein-tagged AQP3 (AQP3-EGFP) revealed that the forskolin-mediated elevation of cAMP increased the diffusion coefficient by 58% from 0.0147 ± 0.0082 μm(2)/s (control) to 0.0232 ± 0.0085 μm(2)/s (forskolin, P < 0.05). Quantum dot-conjugated antibody labeling also revealed a significant increase in AQP3 diffusion upon forskolin treatment by 44% [0.0104 ± 0.0040 μm(2)/s (control) vs. 0.0150 ± 0.0016 μm(2)/s (forskolin, P < 0.05)]. Immunoelectron microscopy showed no obvious difference in AQP3-EGFP expression levels or localization in the plasma membrane upon forskolin stimulation. Thus AQP3-EGFP diffusion is altered upon increased cAMP, which may correspond to basolateral adaptations in response to the increased apical water readsorption.
Collapse
Affiliation(s)
- Saw Marlar
- Institute of Molecular Biology and Genetics and Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, Denmark; and
| | | | | | | | | | | |
Collapse
|
17
|
Arnspang EC, Schwartzentruber J, Clausen MP, Wiseman PW, Lagerholm BC. Bridging the gap between single molecule and ensemble methods for measuring lateral dynamics in the plasma membrane. PLoS One 2013; 8:e78096. [PMID: 24324577 PMCID: PMC3850922 DOI: 10.1371/journal.pone.0078096] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 09/17/2013] [Indexed: 11/22/2022] Open
Abstract
The lateral dynamics of proteins and lipids in the mammalian plasma membrane are heterogeneous likely reflecting both a complex molecular organization and interactions with other macromolecules that reside outside the plane of the membrane. Several methods are commonly used for characterizing the lateral dynamics of lipids and proteins. These experimental and data analysis methods differ in equipment requirements, labeling complexities, and further oftentimes give different results. It would therefore be very convenient to have a single method that is flexible in the choice of fluorescent label and labeling densities from single molecules to ensemble measurements, that can be performed on a conventional wide-field microscope, and that is suitable for fast and accurate analysis. In this work we show that k-space image correlation spectroscopy (kICS) analysis, a technique which was originally developed for analyzing lateral dynamics in samples that are labeled at high densities, can also be used for fast and accurate analysis of single molecule density data of lipids and proteins labeled with quantum dots (QDs). We have further used kICS to investigate the effect of the label size and by comparing the results for a biotinylated lipid labeled at high densities with Atto647N-strepatvidin (sAv) or sparse densities with sAv-QDs. In this latter case, we see that the recovered diffusion rate is two-fold greater for the same lipid and in the same cell-type when labeled with Atto647N-sAv as compared to sAv-QDs. This data demonstrates that kICS can be used for analysis of single molecule data and furthermore can bridge between samples with a labeling densities ranging from single molecule to ensemble level measurements.
Collapse
Affiliation(s)
- Eva C. Arnspang
- Department of Physics, Chemistry and Pharmacy, MEMPHYS-Center for Biomembrane Physics & DaMBIC – Danish Molecular Biomedical Imaging Center, University of Southern Denmark, Odense, Denmark
| | | | - Mathias P. Clausen
- Department of Physics, Chemistry and Pharmacy, MEMPHYS-Center for Biomembrane Physics & DaMBIC – Danish Molecular Biomedical Imaging Center, University of Southern Denmark, Odense, Denmark
| | - Paul W. Wiseman
- Department of Physics and Department of Chemistry, McGill University, Montreal, Canada
| | - B. Christoffer Lagerholm
- Department of Physics, Chemistry and Pharmacy, MEMPHYS-Center for Biomembrane Physics & DaMBIC – Danish Molecular Biomedical Imaging Center, University of Southern Denmark, Odense, Denmark
- * E-mail:
| |
Collapse
|
18
|
Terp MG, Olesen KA, Arnspang EC, Lund RR, Lagerholm BC, Ditzel HJ, Leth-Larsen R. Anti-human CD73 monoclonal antibody inhibits metastasis formation in human breast cancer by inducing clustering and internalization of CD73 expressed on the surface of cancer cells. J Immunol 2013; 191:4165-73. [PMID: 24043904 DOI: 10.4049/jimmunol.1301274] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Recent studies have shown that Abs that target the cell-surface enzyme CD73 (ecto-5'-nucleotidase) reduce growth of primary tumors and metastasis in syngenic mice by inhibiting the catalytic activity of CD73, and thus increasing the activity of cytotoxic T lymphocytes. In this article, we report another anticancer mechanism of anti-CD73 Abs and show that an anti-CD73 mAb (AD2) inhibits metastasis formation by a mechanism independent of CD73 catalytic activity and inhibition of primary tumor growth. This mechanism involves clustering and internalization of CD73, but does not require cross-linking of CD73, because both whole IgG anti-CD73 AD2 mAb and Fab' fragments thereof exhibited this effect. Ex vivo treatment of different breast cancer cell lines with anti-CD73 AD2 mAb before i.v. injection into mice inhibited extravasation/colonization of circulating tumor cells and significantly reduced metastasis development. This effect was also observed when the cancer cell-surface expression of CD73 was significantly reduced by small interfering RNA knockdown. The antimetastatic activity is epitope specific, as another Ab that efficiently binds CD73-expressing live cancer cells did not lead to CD73 internalization and metastasis inhibition. Furthermore, anti-CD73 AD2 mAb inhibited development of metastasis in a spontaneous animal model of human metastatic breast cancer. Our study shows that some anti-CD73 mAbs cause cell-surface clustering of CD73 followed by internalization, thus inhibiting the ability of circulating tumor cells to extravasate and colonize, leading to inhibition of metastasis. Ab-based CD73 cancer therapy should include a combination of Abs that target the catalytic activity of CD73, as well as those with the characteristics described in this article.
Collapse
Affiliation(s)
- Mikkel G Terp
- Department of Cancer and Inflammation Research, Institute of Molecular Medicine, University of Southern Denmark, DK-5000 Odense C, Denmark
| | | | | | | | | | | | | |
Collapse
|
19
|
Rasmussen TE, Jauffred L, Brewer J, Vogel S, Torbensen ER, Lagerholm BC, Oddershede L, Arnspang EC. Single Molecule Applications of Quantum Dots. ACTA ACUST UNITED AC 2013. [DOI: 10.4236/jmp.2013.411a2002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
20
|
Abstract
Quantum dots (QDs) have long promised to revolutionize fluorescence detection to include even applications requiring simultaneous multi-species detection at single molecule sensitivity. Despite the early promise, the unique optical properties of QDs have not yet been fully exploited in e. g. multiplex single molecule sensitivity applications such as single particle tracking (SPT). In order to fully optimize single molecule multiplex application with QDs, we have in this work performed a comprehensive quantitative investigation of the fluorescence intensities, fluorescence intensity fluctuations, and hydrodynamic radii of eight types of commercially available water soluble QDs. In this study, we show that the fluorescence intensity of CdSe core QDs increases as the emission of the QDs shifts towards the red but that hybrid CdSe/CdTe core QDs are less bright than the furthest red-shifted CdSe QDs. We further show that there is only a small size advantage in using blue-shifted QDs in biological applications because of the additional size of the water-stabilizing surface coat. Extending previous work, we finally also show that parallel four color multicolor (MC)-SPT with QDs is possible at an image acquisition rate of at least 25 Hz. We demonstrate the technique by measuring the lateral dynamics of a lipid, biotin-cap-DPPE, in the cellular plasma membrane of live cells using four different colors of QDs; QD565, QD605, QD655, and QD705 as labels.
Collapse
Affiliation(s)
- Eva C. Arnspang
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M, Denmark
- MEMPHYS – Center for Biomembrane Physics, and DaMBIC – Danish Molecular Biomedical Imaging Center, University of Southern Denmark, Odense M, Denmark
| | - Jonathan R. Brewer
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark
- MEMPHYS – Center for Biomembrane Physics, and DaMBIC – Danish Molecular Biomedical Imaging Center, University of Southern Denmark, Odense M, Denmark
| | - B. Christoffer Lagerholm
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M, Denmark
- MEMPHYS – Center for Biomembrane Physics, and DaMBIC – Danish Molecular Biomedical Imaging Center, University of Southern Denmark, Odense M, Denmark
- * E-mail:
| |
Collapse
|
21
|
Clarke AW, Arnspang EC, Mithieux SM, Korkmaz E, Braet F, Weiss AS. Tropoelastin massively associates during coacervation to form quantized protein spheres. Biochemistry 2006; 45:9989-96. [PMID: 16906757 DOI: 10.1021/bi0610092] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tropoelastin, the precursor of elastin, undergoes a rapid monomer to multimer association in an inverse temperature transition. This association culminates in the rapid formation of stable, optically distinct droplets of tropoelastin. Light scattering and microscope measurements reveal that these droplets are 2-6 microm in diameter. Scanning electron microscopy confirms that the droplets are spherical. Three-dimensional confocal image stacks based on the autofluorescence of tropoelastin reveal that droplets are loaded with hydrated tropoelastin. Droplets are viable intermediates in synthetic elastin macroassembly. Dense clusters of aggregated droplets and partially formed fibers develop when droplets are incubated in the presence of a lysyl oxidase. Lysine-reacting chemical and enzyme-assisted cross-linking conditions generate cross-linked beads due to interactions between multiple, surface-exposed lysine epsilon-amino groups. Droplets represent an efficient mechanism for the bolus delivery during elastogenesis of quantized packages of preaccreted tropoelastin.
Collapse
Affiliation(s)
- Adam W Clarke
- School of Molecular and Microbial Biosciences G08, University of Sydney, New South Wales 2006, Australia
| | | | | | | | | | | |
Collapse
|