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Castillo O, Mancillas J, Hughes W, Brancaleon L. Characterization of the interaction of metal-protoporphyrins photosensitizers with β- lactoglobulin. Biophys Chem 2023; 292:106918. [PMID: 36399946 DOI: 10.1016/j.bpc.2022.106918] [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: 07/26/2022] [Revised: 10/24/2022] [Accepted: 10/27/2022] [Indexed: 11/17/2022]
Abstract
We investigated the interaction of a series of metal-protoporphyrins (PPIXs) with bovine β- lactoglobulin (BLG) using a combination of optical spectroscopy and computational simulations. Unlike other studies, the simulations were not merely used to rationalize the experimental data but were employed to refine the experimental data itself. The study was carried out at two pH values, 5 and 9, where BLG is known to have different conformation dictated by the so-called Tanford transition which occurs near pH 7.5. The transition is postulated to regulate access to the interior binding cavity of the protein, thus the pH variation was used as a parameter to investigate whether PPIXs access the central cavity of BLG. The results of our study show that indeed binding increases significantly at alkaline pH, however, the increased affinity is not due to the accessibility of the central cavity. Instead, binding appears to be determined by the tendency of PPIXs to form large inhomogeneous aggregates at acidic pH which hinders interactions with proteins. The binding site determined through a combination of experimental and computational methods is located at the interface between two BLG monomers where the long α-helix segment of the protein face each other. This region is rich in positively charged Lys residues that interact with the propionic acid chains of the protoporphyrins. Establishing the modality of binding between protoporphyrins and BLG would have important consequences for the use of BLG:PPIX complexes in applications such as artificial photoreceptors, artificial metallo-enzymes, delivery of photosensitizers for phototherapy and even solar energy conversion.
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Affiliation(s)
- Omar Castillo
- Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - James Mancillas
- Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - William Hughes
- Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Lorenzo Brancaleon
- Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249, USA.
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2
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Transient Receptor Potential Canonical 5-Scramblase Signaling Complex Mediates Neuronal Phosphatidylserine Externalization and Apoptosis. Cells 2020; 9:cells9030547. [PMID: 32110987 PMCID: PMC7140530 DOI: 10.3390/cells9030547] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 02/24/2020] [Accepted: 02/24/2020] [Indexed: 12/24/2022] Open
Abstract
Phospholipid scramblase 1 (PLSCR1), a lipid-binding and Ca2+-sensitive protein located on plasma membranes, is critically involved in phosphatidylserine (PS) externalization, an important process in cell apoptosis. Transient receptor potential canonical 5 (TRPC5), is a nonselective Ca2+ channel in neurons that interacts with many downstream molecules, participating in diverse physiological functions including temperature or mechanical sensation. The interaction between TRPC5 and PLSCR1 has never been reported. Here, we showed that PLSCR1 interacts with TRPC5 through their C-termini in HEK293 cells and mouse cortical neurons. Formation of TRPC5-PLSCR1 complex stimulates PS externalization and promotes cell apoptosis in HEK293 cells and mouse cerebral neurons. Furthermore, in vivo studies showed that PS externalization in cortical neurons induced by artificial cerebral ischemia-reperfusion was reduced in TRPC5 knockout mice compared to wild-type mice, and that the percentage of apoptotic neurons was also lower in TRPC5 knockout mice than in wild-type mice. Collectively, the present study suggested that TRPC5-PLSCR1 is a signaling complex mediating PS externalization and apoptosis in neurons and that TRPC5 plays a pathological role in cerebral-ischemia reperfusion injury.
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Carravilla P, Darré L, Oar-Arteta IR, Vesga AG, Rujas E, de Las Heras-Martínez G, Domene C, Nieva JL, Requejo-Isidro J. The Bilayer Collective Properties Govern the Interaction of an HIV-1 Antibody with the Viral Membrane. Biophys J 2019; 118:44-56. [PMID: 31787208 DOI: 10.1016/j.bpj.2019.11.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 10/31/2019] [Accepted: 11/05/2019] [Indexed: 01/15/2023] Open
Abstract
Efficient engagement with the envelope glycoprotein membrane-proximal external region (MPER) results in robust blocking of viral infection by a class of broadly neutralizing antibodies (bnAbs) against human immunodeficiency virus (HIV). Developing an accommodation surface that engages with the viral lipid envelope appears to correlate with the neutralizing potency displayed by these bnAbs. The nature of the interactions established between the antibody and the lipid is nonetheless a matter of debate, with some authors arguing that anti-MPER specificity arises only under pathological conditions in autoantibodies endowed with stereospecific binding sites for phospholipids. However, bnAb-lipid interactions are often studied in systems that do not fully preserve the biophysical properties of lipid bilayers, and therefore, questions on binding specificity and the effect of collective membrane properties on the interaction are still open. Here, to evaluate the specificity of lipid interactions of an anti-MPER bnAb (4E10) in an intact membrane context, we determine quantitatively its association with lipid bilayers by means of scanning fluorescence correlation spectroscopy and all-atom molecular dynamic simulations. Our data support that 4E10 establishes electrostatic and hydrophobic interactions with the viral membrane surface and that the collective physical properties of the lipid bilayer influence 4E10 dynamics therein. We conclude that establishment of peripheral, nonspecific electrostatic interactions with the viral membrane through accommodation surfaces may assist high-affinity binding of HIV-1 MPER epitope at membrane interfaces. These findings highlight the importance of considering antibody-lipid interactions in the design of antibody-based anti-HIV strategies.
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Affiliation(s)
- Pablo Carravilla
- Instituto Biofisika (CSIC, UPV/EHU), Barrio Sarriena s/n, Leioa, Spain; Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Bilbao, Spain; Institute of Applied Optics and Biophysics, Friedrich-Schiller-University Jena, Jena, Germany
| | - Leonardo Darré
- Functional Genomics Laboratory & Biomolecular Simulations Laboratory, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Itziar R Oar-Arteta
- Instituto Biofisika (CSIC, UPV/EHU), Barrio Sarriena s/n, Leioa, Spain; Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Bilbao, Spain
| | - Arturo G Vesga
- Instituto Biofisika (CSIC, UPV/EHU), Barrio Sarriena s/n, Leioa, Spain; Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Bilbao, Spain
| | - Edurne Rujas
- Instituto Biofisika (CSIC, UPV/EHU), Barrio Sarriena s/n, Leioa, Spain; Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Bilbao, Spain
| | | | - Carmen Domene
- Department of Chemistry, University of Bath, Claverton Down, Bath, United Kingdom; Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Jose L Nieva
- Instituto Biofisika (CSIC, UPV/EHU), Barrio Sarriena s/n, Leioa, Spain; Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Bilbao, Spain.
| | - Jose Requejo-Isidro
- Instituto Biofisika (CSIC, UPV/EHU), Barrio Sarriena s/n, Leioa, Spain; Centro Nacional de Biotecnología, CSIC, Madrid, Spain; Unidad de Nanobiotecnología, CNB-CSIC-IMDEA Nanociencia Associated Unit, Madrid, Spain.
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Heras-Martínez GDL, Calleja V, Bailly R, Dessolin J, Larijani B, Requejo-Isidro J. A Complex Interplay of Anionic Phospholipid Binding Regulates 3'-Phosphoinositide-Dependent-Kinase-1 Homodimer Activation. Sci Rep 2019; 9:14527. [PMID: 31601855 PMCID: PMC6787260 DOI: 10.1038/s41598-019-50742-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 09/16/2019] [Indexed: 12/28/2022] Open
Abstract
3'-Phosphoinositide-dependent-Kinase-1 (PDK1) is a master regulator whereby its PI3-kinase-dependent dysregulation in human pathologies is well documented. Understanding the direct role for PtdIns(3,4,5)P3 and other anionic phospholipids in the regulation of PDK1 conformational dynamics and its downstream activation remains incomplete. Using advanced quantitative-time-resolved imaging (Fluorescence Lifetime Imaging and Fluorescence Correlation Spectroscopy) and molecular modelling, we show an interplay of antagonistic binding effects of PtdIns(3,4,5)P3 and other anionic phospholipids, regulating activated PDK1 homodimers. We demonstrate that phosphatidylserine maintains PDK1 in an inactive conformation. The dysregulation of the PI3K pathway affects the spatio-temporal and conformational dynamics of PDK1 and the activation of its downstream substrates. We have established a new anionic-phospholipid-dependent model for PDK1 regulation, depicting the conformational dynamics of multiple homodimer states. We show that the dysregulation of the PI3K pathway perturbs equilibrium between the PDK1 homodimer conformations. Our findings provide a role for the PtdSer binding site and its previously unrewarding role in PDK1 downregulation, suggesting a possible therapeutic strategy where the constitutively active dimer conformer of PDK1 may be rendered inactive by small molecules that drive it to its PtdSer-bound conformer.
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Affiliation(s)
- Gloria de Las Heras-Martínez
- Instituto Biofisika (CSIC, UPV/EHU), 48490, Leioa, Spain
- Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Instituto Biofisika (CSIC, UPV/EHU) & Research Centre for Experimental Marine Biology and Biotechnology (PiE), University of the Basque Country (UPV/EHU), Leioa, 48940, Spain
| | - Véronique Calleja
- Protein Phosphorylation Laboratory, The Francis Crick Institute, 1 Midland Road, NW1 1AT, London, UK
| | - Remy Bailly
- Institute of Chemistry & Biology of Membranes & Nanoobjects (UMR 5248 CBMN) CNRS - Université de Bordeaux - Bordeaux INP All. Geoffroy Saint-Hilaire, 33600, Pessac, France
| | - Jean Dessolin
- Institute of Chemistry & Biology of Membranes & Nanoobjects (UMR 5248 CBMN) CNRS - Université de Bordeaux - Bordeaux INP All. Geoffroy Saint-Hilaire, 33600, Pessac, France
| | - Banafshé Larijani
- Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Instituto Biofisika (CSIC, UPV/EHU) & Research Centre for Experimental Marine Biology and Biotechnology (PiE), University of the Basque Country (UPV/EHU), Leioa, 48940, Spain.
- Centre for Therapeutic Innovation (CTI-Bath); Cell Biophysics Laboratory Department of Pharmacy & Pharmacology University, Bath, Claverton Down, Bath, BA2 7AY, United Kingdom.
| | - Jose Requejo-Isidro
- Instituto Biofisika (CSIC, UPV/EHU), 48490, Leioa, Spain.
- Centro Nacional de Biotecnología (CSIC), Darwin, 3, E28049, Madrid, Spain.
- Unidad de Nanobiotecnología, CNB-CSIC-IMDEA Nanociencia Associated Unit, 28049, Madrid, Spain.
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Zhang C, Liu Y, Qu W, Su W, Du M, Yang F, Chen T. ExEm-FRET two-hybrid assay: FRET two-hybrid assay based on linear unmixing of excitation-emission spectra. OPTICS EXPRESS 2019; 27:18282-18295. [PMID: 31252774 DOI: 10.1364/oe.27.018282] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Accepted: 06/03/2019] [Indexed: 06/09/2023]
Abstract
Simultaneous linear unmixing of excitation-emission spectra (ExEm-unmixing)-based fluorescence resonance energy transfer (FRET) two-hybrid assay method, named as ExEm-FRET two-hybrid assay, was developed for evaluating the stoichiometric ratio of macromolecular complexes in living cells. Linear unmixing of the excitation-emission spectra (SDA) of cells obtains the weight factors of donor (WD), acceptor (WA) and acceptor sensitization (WS), yielding ED and EA (donor- and acceptor-centric FRET efficiency) images. ExEm-FRET two-hybrid assay employs pixel-to-pixel titration curves of ED/EA versus the free acceptor (Ca)/donor (Cd) concentration deduced from the three weight factors to obtain EA,max and ED,max (the maximal EA and ED), thus yielding the stoichiometric ratio (EA,max/ED,max) of donor-tagged protein to acceptor-tagged protein.
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Hochreiter B, Kunze M, Moser B, Schmid JA. Advanced FRET normalization allows quantitative analysis of protein interactions including stoichiometries and relative affinities in living cells. Sci Rep 2019; 9:8233. [PMID: 31160659 PMCID: PMC6547726 DOI: 10.1038/s41598-019-44650-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 05/20/2019] [Indexed: 12/31/2022] Open
Abstract
FRET (Fluorescence Resonance Energy Transfer) measurements are commonly applied to proof protein-protein interactions. However, standard methods of live cell FRET microscopy and signal normalization only allow a principle assessment of mutual binding and are unable to deduce quantitative information of the interaction. We present an evaluation and normalization procedure for 3-filter FRET measurements, which reflects the process of complex formation by plotting FRET-saturation curves. The advantage of this approach relative to traditional signal normalizations is demonstrated by mathematical simulations. Thereby, we also identify the contribution of critical parameters such as the total amount of donor and acceptor molecules and their molar ratio. When combined with a fitting procedure, this normalization facilitates the extraction of key properties of protein complexes such as the interaction stoichiometry or the apparent affinity of the binding partners. Finally, the feasibility of our method is verified by investigating three exemplary protein complexes. Altogether, our approach offers a novel method for a quantitative analysis of protein interactions by 3-filter FRET microscopy, as well as flow cytometry. To facilitate the application of this method, we created macros and routines for the programs ImageJ, R and MS-Excel, which we make publicly available.
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Affiliation(s)
- Bernhard Hochreiter
- Medical University Vienna, Center for Physiology and Pharmacology, Institute for Vascular Biology and Thrombosis Research, Vienna, Austria
| | - Markus Kunze
- Medical University Vienna, Center for Brain Research, Department of Pathobiology of the Nervous System, Vienna, Austria
| | - Bernhard Moser
- Medical University Vienna, Center for Physiology and Pharmacology, Institute for Vascular Biology and Thrombosis Research, Vienna, Austria
| | - Johannes A Schmid
- Medical University Vienna, Center for Physiology and Pharmacology, Institute for Vascular Biology and Thrombosis Research, Vienna, Austria.
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