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Struts AV, Barmasov AV, Fried SDE, Hewage KSK, Perera SMDC, Brown MF. Osmotic stress studies of G-protein-coupled receptor rhodopsin activation. Biophys Chem 2024; 304:107112. [PMID: 37952496 DOI: 10.1016/j.bpc.2023.107112] [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: 05/06/2023] [Revised: 09/22/2023] [Accepted: 09/24/2023] [Indexed: 11/14/2023]
Abstract
We summarize and critically review osmotic stress studies of the G-protein-coupled receptor rhodopsin. Although small amounts of structural water are present in these receptors, the effect of bulk water on their function remains uncertain. Studies of the influences of osmotic stress on the GPCR archetype rhodopsin have given insights into the functional role of water in receptor activation. Experimental work has discovered that osmolytes shift the metarhodopsin equilibrium after photoactivation, either to the active or inactive conformations according to their molar mass. At least 80 water molecules are found to enter rhodopsin in the transition to the photoreceptor active state. We infer that this movement of water is both necessary and sufficient for receptor activation. If the water influx is prevented, e.g., by large polymer osmolytes or by dehydration, then the receptor functional transition is back shifted. These findings imply a new paradigm in which rhodopsin becomes solvent swollen in the activation mechanism. Water thus acts as an allosteric modulator of function for rhodopsin-like receptors in lipid membranes.
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Affiliation(s)
- Andrey V Struts
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA; Laboratory of Biomolecular NMR, St.-Petersburg State University, 199034 St.-Petersburg, Russia
| | - Alexander V Barmasov
- Department of Biophysics, St.-Petersburg State Pediatric Medical University, 194100 St.-Petersburg, Russia; Department of Physics, St.-Petersburg State University, 199034 St.-Petersburg, Russia
| | - Steven D E Fried
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Kushani S K Hewage
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | | | - Michael F Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA; Department of Physics, University of Arizona, Tucson, AZ 85721, USA.
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2
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Han CT, Nguyen KDQ, Berkow MW, Hussain S, Kiani A, Kinnebrew M, Idso MN, Baxter N, Chang E, Aye E, Winslow E, Rahman M, Seppälä S, O'Malley MA, Chmelka BF, Mertz B, Han S. Lipid membrane mimetics and oligomerization tune functional properties of proteorhodopsin. Biophys J 2023; 122:168-179. [PMID: 36352784 PMCID: PMC9822798 DOI: 10.1016/j.bpj.2022.11.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 08/01/2022] [Accepted: 11/07/2022] [Indexed: 11/10/2022] Open
Abstract
The functional properties of proteorhodopsin (PR) have been found to be strongly modulated by oligomeric distributions and lipid membrane mimetics. This study aims to distinguish and explain their effects by investigating how oligomer formation impacts PR's function of proton transport in lipid-based membrane mimetic environments. We find that PR forms stable hexamers and pentamers in both E. coli membranes and synthetic liposomes. Compared with the monomers, the photocycle kinetics of PR oligomers is ∼2 and ∼4.5 times slower for transitions between the K and M and the M and N photointermediates, respectively, indicating that oligomerization significantly slows PR's rate of proton transport in liposomes. In contrast, the apparent pKa of the key proton acceptor residue D97 (pKaD97) of liposome-embedded PR persists at 6.2-6.6, regardless of cross-protomer modulation of D97, suggesting that the liposome environment helps maintain PR's functional activity at neutral pH. By comparison, when extracted directly from E. coli membranes into styrene-maleic acid lipid particles, the pKaD97 of monomer-enriched E50Q PR drastically increases to 8.9, implying that there is a very low active PR population at neutral pH to engage in PR's photocycle. These findings demonstrate that oligomerization impacts PR's photocycle kinetics, while lipid-based membrane mimetics strongly affect PR's active population via different mechanisms.
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Affiliation(s)
- Chung-Ta Han
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California
| | - Khanh Dinh Quoc Nguyen
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California
| | - Maxwell W Berkow
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California
| | - Sunyia Hussain
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California
| | - Ahmad Kiani
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia
| | - Maia Kinnebrew
- College of Creative Studies, Biology Department, University of California, Santa Barbara, Santa Barbara, California
| | - Matthew N Idso
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California
| | - Naomi Baxter
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California
| | - Evelyn Chang
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California
| | - Emily Aye
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California
| | - Elsa Winslow
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California
| | - Mohammad Rahman
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia
| | - Susanna Seppälä
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California
| | - Michelle A O'Malley
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California
| | - Bradley F Chmelka
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California
| | - Blake Mertz
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia
| | - Songi Han
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California; Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California.
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3
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Chawla U, Chopra D. Structural Advancement in Shoc2‐MAPK Signaling Pathways in the Treatment of Cancer and Other Diseases. ChemistrySelect 2022. [DOI: 10.1002/slct.202203791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Udeep Chawla
- Innovation and Incubation Centre for Entrepreneurship Indian Institute of Science Education and Research Bhopal Bhopal 462066 Madhya Pradesh India
- The University of Arizona, Department of Chemistry and Biochemistry Tucson AZ85721 United States
| | - Deepak Chopra
- Innovation and Incubation Centre for Entrepreneurship Indian Institute of Science Education and Research Bhopal Bhopal 462066 Madhya Pradesh India
- Department of Chemistry Indian Institute of Science Education and Research Bhopal Bhopal 462066 Madhya Pradesh India
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4
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Abstract
Although G-protein–coupled receptors (GPCRs) control vast physiological pathways, their activation remains chemically and physically enigmatic. Our osmotic stress studies of the visual receptor rhodopsin have redefined the standard model of GPCR signaling by revealing the essential role of bulk water. We show results consistent with a large number of water molecules flooding the rhodopsin interior during activation to stabilize the effector binding conformation. These results suggest a model of GPCR activation in which the receptor becomes solvent-swollen upon formation of the active state. We thus demonstrate the mechanism whereby water acts as a powerful allosteric modulator of a pharmacologically important membrane protein family. The Rhodopsin family of G-protein–coupled receptors (GPCRs) comprises the targets of nearly a third of all pharmaceuticals. Despite structural water present in GPCR X-ray structures, the physiological relevance of these solvent molecules to rhodopsin signaling remains unknown. Here, we show experimental results consistent with the idea that rhodopsin activation in lipid membranes is coupled to bulk water movements into the protein. To quantify hydration changes, we measured reversible shifting of the metarhodopsin equilibrium due to osmotic stress using an extensive series of polyethylene glycol (PEG) osmolytes. We discovered clear evidence that light activation entails a large influx of bulk water (∼80–100 molecules) into the protein, giving insight into GPCR activation mechanisms. Various size polymer osmolytes directly control rhodopsin activation, in which large solutes are excluded from rhodopsin and dehydrate the protein, favoring the inactive state. In contrast, small osmolytes initially forward shift the activation equilibrium until a quantifiable saturation point is reached, similar to gain-of-function protein mutations. For the limit of increasing osmolyte size, a universal response of rhodopsin to osmotic stress is observed, suggesting it adopts a dynamic, hydrated sponge-like state upon photoactivation. Our results demand a rethinking of the role of water dynamics in modulating various intermediates in the GPCR energy landscape. We propose that besides bound water, an influx of bulk water plays a necessary role in establishing the active GPCR conformation that mediates signaling.
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5
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Chawla U, Kashyap MK, Husain A. Aging and diabetes drive the COVID-19 forwards; unveiling nature and existing therapies for the treatment. Mol Cell Biochem 2021; 476:3911-3922. [PMID: 34169437 PMCID: PMC8224992 DOI: 10.1007/s11010-021-04200-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 05/27/2021] [Indexed: 02/07/2023]
Abstract
Human SARS Coronavirus-2 (SARS-CoV-2) has infected more than 170 million people worldwide and resulted in more than 3.5 million deaths so far. The infection causes Coronavirus disease (COVID-19) in people of all age groups, notably diabetic and old age people, at a higher risk of infectivity and fatality. Around 35% of the patients who have died of the disease were diabetic. The infection is associated with weakening immune response, chronic inflammation, and potential direct pancreatic impairment. There seems to be a three-way association of the SARS-CoV-2 infection with diabetes and aging. The COVID-19 infection causes metabolism complications, which may induce diabetes and accelerate aging in healthy individuals. How does diabetes elevate the likelihood of the infection is not clearly understood. we summarize mechanisms of accelerated aging in COVID-19 and diabetes, and the possible correlation of these three diseases. Various drug candidates under different stages of pre-clinical or clinical developments give us hope for the development of COVID-19 therapeutics, but there is no approved drug so far to treat this disease. Here, we explored the potential of anti-diabetic and anti-aging natural compounds for the COVID-19 treatment. We have also reviewed different therapeutic strategies with plant-based natural products that may be used to cure patients infected with SARS-CoV-2 and post-infection syndrome.
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Affiliation(s)
- Udeep Chawla
- Department of Chemistry and Biochemistry, The University of Arizona, Old Chemistry 226, Tucson, AZ, 85721, USA
| | - Manoj Kumar Kashyap
- Amity Stem Cell Institute, Amity Medical School, Amity University Haryana, Amity Education Valley Panchgaon, Manesar (Gurugram), Haryana, India
| | - Amjad Husain
- Centre for Science & Society, Indian Institute of Science Education and Research (IISER), Bhopal, Madhya Pradesh, India.
- Innovation and Incubation Centre for Entrepreneurship, Indian Institute of Science Education and Research (IISER), Bhopal, Madhya Pradesh, India.
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6
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Chawla U, Kashyap MK, Husain A. Aging and diabetes drive the COVID-19 forwards; unveiling nature and existing therapies for the treatment. Mol Cell Biochem 2021. [PMID: 34169437 DOI: 10.1007/s11010-021-04200-7,] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/29/2022]
Abstract
Human SARS Coronavirus-2 (SARS-CoV-2) has infected more than 170 million people worldwide and resulted in more than 3.5 million deaths so far. The infection causes Coronavirus disease (COVID-19) in people of all age groups, notably diabetic and old age people, at a higher risk of infectivity and fatality. Around 35% of the patients who have died of the disease were diabetic. The infection is associated with weakening immune response, chronic inflammation, and potential direct pancreatic impairment. There seems to be a three-way association of the SARS-CoV-2 infection with diabetes and aging. The COVID-19 infection causes metabolism complications, which may induce diabetes and accelerate aging in healthy individuals. How does diabetes elevate the likelihood of the infection is not clearly understood. we summarize mechanisms of accelerated aging in COVID-19 and diabetes, and the possible correlation of these three diseases. Various drug candidates under different stages of pre-clinical or clinical developments give us hope for the development of COVID-19 therapeutics, but there is no approved drug so far to treat this disease. Here, we explored the potential of anti-diabetic and anti-aging natural compounds for the COVID-19 treatment. We have also reviewed different therapeutic strategies with plant-based natural products that may be used to cure patients infected with SARS-CoV-2 and post-infection syndrome.
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Affiliation(s)
- Udeep Chawla
- Department of Chemistry and Biochemistry, The University of Arizona, Old Chemistry 226, Tucson, AZ, 85721, USA
| | - Manoj Kumar Kashyap
- Amity Stem Cell Institute, Amity Medical School, Amity University Haryana, Amity Education Valley Panchgaon, Manesar (Gurugram), Haryana, India
| | - Amjad Husain
- Centre for Science & Society, Indian Institute of Science Education and Research (IISER), Bhopal, Madhya Pradesh, India. .,Innovation and Incubation Centre for Entrepreneurship, Indian Institute of Science Education and Research (IISER), Bhopal, Madhya Pradesh, India.
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7
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Chawla U, Perera SMDC, Fried SDE, Eitel AR, Mertz B, Weerasinghe N, Pitman MC, Struts AV, Brown MF. Activation of the G‐Protein‐Coupled Receptor Rhodopsin by Water. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202003342] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Udeep Chawla
- Department of Chemistry and Biochemistry University of Arizona Tucson AZ 85721 USA
| | | | - Steven D. E. Fried
- Department of Chemistry and Biochemistry University of Arizona Tucson AZ 85721 USA
| | - Anna R. Eitel
- Department of Chemistry and Biochemistry University of Arizona Tucson AZ 85721 USA
| | - Blake Mertz
- Department of Chemistry and Biochemistry University of Arizona Tucson AZ 85721 USA
| | - Nipuna Weerasinghe
- Department of Chemistry and Biochemistry University of Arizona Tucson AZ 85721 USA
| | - Michael C. Pitman
- Department of Chemistry and Biochemistry University of Arizona Tucson AZ 85721 USA
| | - Andrey V. Struts
- Department of Chemistry and Biochemistry University of Arizona Tucson AZ 85721 USA
- Laboratory of Biomolecular NMR St. Petersburg State University St. Petersburg 199034 Russia
| | - Michael F. Brown
- Department of Chemistry and Biochemistry University of Arizona Tucson AZ 85721 USA
- Department of Physics University of Arizona Tucson AZ 85721 USA
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8
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Chawla U, Perera SMDC, Fried SDE, Eitel AR, Mertz B, Weerasinghe N, Pitman MC, Struts AV, Brown MF. Activation of the G-Protein-Coupled Receptor Rhodopsin by Water. Angew Chem Int Ed Engl 2020; 60:2288-2295. [PMID: 32596956 DOI: 10.1002/anie.202003342] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 05/28/2020] [Indexed: 12/31/2022]
Abstract
Visual rhodopsin is an important archetype for G-protein-coupled receptors, which are membrane proteins implicated in cellular signal transduction. Herein, we show experimentally that approximately 80 water molecules flood rhodopsin upon light absorption to form a solvent-swollen active state. An influx of mobile water is necessary for activating the photoreceptor, and this finding is supported by molecular dynamics (MD) simulations. Combined force-based measurements involving osmotic and hydrostatic pressure indicate the expansion occurs by changes in cavity volumes, together with greater hydration in the active metarhodopsin-II state. Moreover, we discovered that binding and release of the C-terminal helix of transducin is coupled to hydration changes as may occur in visual signal amplification. Hydration-dehydration explains signaling by a dynamic allosteric mechanism, in which the soft membrane matter (lipids and water) has a pivotal role in the catalytic G-protein cycle.
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Affiliation(s)
- Udeep Chawla
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | | | - Steven D E Fried
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - Anna R Eitel
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - Blake Mertz
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - Nipuna Weerasinghe
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - Michael C Pitman
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - Andrey V Struts
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA.,Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, 199034, Russia
| | - Michael F Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA.,Department of Physics, University of Arizona, Tucson, AZ, 85721, USA
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9
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Han CT, Song J, Chan T, Pruett C, Han S. Electrostatic Environment of Proteorhodopsin Affects the pKa of Its Buried Primary Proton Acceptor. Biophys J 2020; 118:1838-1849. [PMID: 32197061 DOI: 10.1016/j.bpj.2020.02.027] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 01/27/2020] [Accepted: 02/27/2020] [Indexed: 01/18/2023] Open
Abstract
The protonation state of embedded charged residues in transmembrane proteins (TMPs) can control the onset of protein function. It is understood that interactions between an embedded charged residue and other charged or polar residues in the moiety would influence its pKa, but how the surrounding environment in which the TMP resides affects the pKa of these residues is unclear. Proteorhodopsin (PR), a light-responsive proton pump from marine bacteria, was used as a model to examine externally accessible factors that tune the pKa of its embedded charged residue, specifically its primary proton acceptor D97. The pKa of D97 was compared between PR reconstituted in liposomes with different net headgroup charges and equilibrated in buffer with different ion concentrations. For PR reconstituted in net positively charged compared to net negatively charged liposomes in low-salt buffer solutions, a drop of the apparent pKa from 7.6 to 5.6 was observed, whereas intrinsic pKa modeled with surface pH calculated from Gouy-Chapman predictions found an opposite trend for the pKa change, suggesting that surface pH does not account for the main changes observed in the apparent pKa. This difference in the pKa of D97 observed from PR reconstituted in oppositely charged liposome environments disappeared when the NaCl concentration was increased to 150 mM. We suggest that protein-intrinsic structural properties must play a role in adjusting the local microenvironment around D97 to affect its pKa, as corroborated with observations of changes in protein side-chain and hydration dynamics around the E-F loop of PR. Understanding the effect of externally controllable factors in tuning the pKa of TMP-embedded charged residues is important for bioengineering and biomedical applications relying on TMP systems, in which the onset of functions can be controlled by the protonation state of embedded residues.
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Affiliation(s)
- Chung-Ta Han
- Department of Chemical Engineering, University of California, Santa Barbara, California
| | - Jichao Song
- Department of Chemical Engineering, University of California, Santa Barbara, California
| | - Tristan Chan
- Department of Chemistry, University of California, Santa Barbara, California
| | - Christine Pruett
- Department of Chemical Engineering, University of California, Santa Barbara, California
| | - Songi Han
- Department of Chemical Engineering, University of California, Santa Barbara, California; Department of Chemistry, University of California, Santa Barbara, California.
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10
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Molugu TR, Oita RC, Chawla U, Camp SM, Brown MF, Garcia JGN. Nicotinamide phosphoribosyltransferase purification using SUMO expression system. Anal Biochem 2020; 598:113597. [PMID: 31982408 DOI: 10.1016/j.ab.2020.113597] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2019] [Revised: 01/15/2020] [Accepted: 01/20/2020] [Indexed: 02/08/2023]
Abstract
Nicotinamide phosphoribosyltransferase (NAMPT) is a rate-limiting enzyme in the salvage pathway required for nicotinamide adenine dinucleotide synthesis. The secreted NAMPT protein serves as a master regulatory cytokine involved in activation of evolutionarily conserved inflammatory networks. Appreciation of the role of NAMPT as a damage-associated molecular pattern protein (DAMP) has linked its activities to several disorders via Toll-like receptor 4 (TLR4) binding and inflammatory cascade activation. Information is currently lacking concerning the precise mode of the NAMPT protein functionality due to limited availability of purified protein for use in in vitro and in vivo studies. Here we report successful NAMPT expression using the pET-SUMO expression vector in E. coli strain SHuffle containing a hexa-His tag for purification. The Ulp1 protease was used to cleave the SUMO and hexa-His tags, and the protein was purified by immobilized-metal affinity chromatography. The protein yield was ~4 mg/L and initial biophysical characterization of the protein using circular dichroism revealed the secondary structural elements, while dynamic light scattering demonstrated the presence of oligomeric units. The NAMPT-SUMO showed a predominantly dimeric protein with functional enzymatic activity. Finally, we report NAMPT solubilization in n-dodecyl-β-d-maltopyranoside (DDM) detergent in monomeric form, thus enhancing the opportunity for further structural and functional investigations.
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Affiliation(s)
- Trivikram R Molugu
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - Radu C Oita
- Department of Medicine, University of Arizona Health Sciences, University of Arizona, Tucson, AZ, 85721, USA
| | - Udeep Chawla
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - Sara M Camp
- Department of Medicine, University of Arizona Health Sciences, University of Arizona, Tucson, AZ, 85721, USA
| | - Michael F Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA; Department of Physics, University of Arizona, Tucson, AZ, 85721, USA.
| | - Joe G N Garcia
- Department of Medicine, University of Arizona Health Sciences, University of Arizona, Tucson, AZ, 85721, USA.
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Molugu TR, Brown MF. Cholesterol Effects on the Physical Properties of Lipid Membranes Viewed by Solid-state NMR Spectroscopy. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1115:99-133. [PMID: 30649757 DOI: 10.1007/978-3-030-04278-3_5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In this chapter, we review the physical properties of lipid/cholesterol mixtures involving studies of model membranes using solid-state NMR spectroscopy. The approach allows one to quantify the average membrane structure, fluctuations, and elastic deformation upon cholesterol interaction. Emphasis is placed on understanding the membrane structural deformation and emergent fluctuations at an atomistic level. Lineshape measurements using solid-state NMR spectroscopy give equilibrium structural properties, while relaxation time measurements study the molecular dynamics over a wide timescale range. The equilibrium properties of glycerophospholipids, sphingolipids, and their binary and tertiary mixtures with cholesterol are accessible. Nonideal mixing of cholesterol with other lipids explains the occurrence of liquid-ordered domains. The entropic loss upon addition of cholesterol to sphingolipids is less than for glycerophospholipids, and may drive formation of lipid rafts. The functional dependence of 2H NMR spin-lattice relaxation (R 1Z) rates on segmental order parameters (S CD) for lipid membranes is indicative of emergent viscoelastic properties. Addition of cholesterol shows stiffening of the bilayer relative to the pure lipids and this effect is diminished for lanosterol. Opposite influences of cholesterol and detergents on collective dynamics and elasticity at an atomistic scale can potentially affect lipid raft formation in cellular membranes.
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Affiliation(s)
- Trivikram R Molugu
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
| | - Michael F Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA. .,Department of Physics, University of Arizona, Tucson, AZ, USA.
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12
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Polymer Nanodiscs: Discoidal Amphiphilic Block Copolymer Membranes as a New Platform for Membrane Proteins. Sci Rep 2017; 7:15227. [PMID: 29123151 PMCID: PMC5680229 DOI: 10.1038/s41598-017-15151-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 10/18/2017] [Indexed: 12/23/2022] Open
Abstract
Lipid nanodiscs are playing increasingly important roles in studies of the structure and function of membrane proteins. Development of lipid nanodiscs as a membrane-protein-supporting platform, or a drug targeting and delivery vehicle in general, is undermined by the fluidic and labile nature of lipid bilayers. Here, we report the discovery of polymer nanodiscs, i.e., discoidal amphiphilic block copolymer membrane patches encased within membrane scaffold proteins, as a novel two-dimensional nanomembrane that maintains the advantages of lipid nanodiscs while addressing their weaknesses. Using MsbA, a bacterial ATP-binding cassette transporter as a membrane protein prototype, we show that the protein can be reconstituted into the polymer nanodiscs in an active state. As with lipid nanodiscs, reconstitution of detergent-solubilized MsbA into the polymer nanodiscs significantly enhances its activity. In contrast to lipid nanodiscs that undergo time- and temperature-dependent structural changes, the polymer nanodiscs experience negligible structural evolution under similar environmental stresses, revealing a critically important property for the development of nanodisc-based characterization methodologies or biotechnologies. We expect that the higher mechanical and chemical stability of block copolymer membranes and their chemical versatility for adaptation will open new opportunities for applications built upon diverse membrane protein functions, or involved with drug targeting and delivery.
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13
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Molugu TR, Lee S, Brown MF. Concepts and Methods of Solid-State NMR Spectroscopy Applied to Biomembranes. Chem Rev 2017; 117:12087-12132. [PMID: 28906107 DOI: 10.1021/acs.chemrev.6b00619] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Concepts of solid-state NMR spectroscopy and applications to fluid membranes are reviewed in this paper. Membrane lipids with 2H-labeled acyl chains or polar head groups are studied using 2H NMR to yield knowledge of their atomistic structures in relation to equilibrium properties. This review demonstrates the principles and applications of solid-state NMR by unifying dipolar and quadrupolar interactions and highlights the unique features offered by solid-state 2H NMR with experimental illustrations. For randomly oriented multilamellar lipids or aligned membranes, solid-state 2H NMR enables direct measurement of residual quadrupolar couplings (RQCs) due to individual C-2H-labeled segments. The distribution of RQC values gives nearly complete profiles of the segmental order parameters SCD(i) as a function of acyl segment position (i). Alternatively, one can measure residual dipolar couplings (RDCs) for natural abundance lipid samples to obtain segmental SCH order parameters. A theoretical mean-torque model provides acyl-packing profiles representing the cumulative chain extension along the normal to the aqueous interface. Equilibrium structural properties of fluid bilayers and various thermodynamic quantities can then be calculated, which describe the interactions with cholesterol, detergents, peptides, and integral membrane proteins and formation of lipid rafts. One can also obtain direct information for membrane-bound peptides or proteins by measuring RDCs using magic-angle spinning (MAS) in combination with dipolar recoupling methods. Solid-state NMR methods have been extensively applied to characterize model membranes and membrane-bound peptides and proteins, giving unique information on their conformations, orientations, and interactions in the natural liquid-crystalline state.
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Affiliation(s)
- Trivikram R Molugu
- Department of Chemistry & Biochemistry and ‡Department of Physics, University of Arizona , Tucson, Arizona 85721, United States
| | - Soohyun Lee
- Department of Chemistry & Biochemistry and ‡Department of Physics, University of Arizona , Tucson, Arizona 85721, United States
| | - Michael F Brown
- Department of Chemistry & Biochemistry and ‡Department of Physics, University of Arizona , Tucson, Arizona 85721, United States
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14
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Sandoval-Perez A, Pluhackova K, Böckmann RA. Critical Comparison of Biomembrane Force Fields: Protein-Lipid Interactions at the Membrane Interface. J Chem Theory Comput 2017; 13:2310-2321. [PMID: 28388089 DOI: 10.1021/acs.jctc.7b00001] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Molecular dynamics (MD) simulations offer the possibility to study biological processes at high spatial and temporal resolution often not reachable by experiments. Corresponding biomolecular force field parameters have been developed for a wide variety of molecules ranging from inorganic ligands and small organic molecules over proteins and lipids to nucleic acids. Force fields have typically been parametrized and validated on thermodynamic observables and structural characteristics of individual compounds, e.g. of soluble proteins or lipid bilayers. Less strictly, due to the added complexity and missing experimental data to compare to, force fields have hardly been tested on the properties of mixed systems, e.g. on protein-lipid systems. Their selection and combination for mixed systems is further complicated by the partially differing parametrization strategies. Additionally, the presence of other compounds in the system may shift the subtle balance of force field parameters. Here, we assessed the protein-lipid interactions as described in the four atomistic force fields GROMOS54a7, CHARMM36 and the two force field combinations Amber14sb/Slipids and Amber14sb/Lipid14. Four observables were compared, focusing on the membrane-water interface: the conservation of the secondary structure of transmembrane proteins, the positioning of transmembrane peptides relative to the lipid bilayer, the insertion depth of side chains of unfolded peptides absorbed at the membrane interface, and the ability to reproduce experimental insertion energies of Wimley-White peptides at the membrane interface. Significant differences between the force fields were observed that affect e.g. membrane insertion depths and tilting of transmembrane peptides.
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Affiliation(s)
- Angelica Sandoval-Perez
- Computational Biology, Department of Biology, Friedrich-Alexander University of Erlangen-Nürnberg , Staudtstrassre 5, 91058 Erlangen, Germany
| | - Kristyna Pluhackova
- Computational Biology, Department of Biology, Friedrich-Alexander University of Erlangen-Nürnberg , Staudtstrassre 5, 91058 Erlangen, Germany
| | - Rainer A Böckmann
- Computational Biology, Department of Biology, Friedrich-Alexander University of Erlangen-Nürnberg , Staudtstrassre 5, 91058 Erlangen, Germany
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15
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Calmet P, De Maria M, Harté E, Lamb D, Serrano-Vega M, Jazayeri A, Tschammer N, Alves ID. Real time monitoring of membrane GPCR reconstitution by plasmon waveguide resonance: on the role of lipids. Sci Rep 2016; 6:36181. [PMID: 27824122 PMCID: PMC5099921 DOI: 10.1038/srep36181] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 10/12/2016] [Indexed: 01/14/2023] Open
Abstract
G-protein coupled receptors (GPCRs) are important therapeutic targets since more than 40% of the drugs on the market exert their action through these proteins. To decipher the molecular mechanisms of activation and signaling, GPCRs often need to be isolated and reconstituted from a detergent-solubilized state into a well-defined and controllable lipid model system. Several methods exist to reconstitute membrane proteins in lipid systems but usually the reconstitution success is tested at the end of the experiment and often by an additional and indirect method. Irrespective of the method used, the reconstitution process is often an intractable and time-consuming trial-and-error procedure. Herein, we present a method that allows directly monitoring the reconstitution of GPCRs in model planar lipid membranes. Plasmon waveguide resonance (PWR) allows following GPCR lipid reconstitution process without any labeling and with high sensitivity. Additionally, the method is ideal to probe the lipid effect on receptor ligand binding as demonstrated by antagonist binding to the chemokine CCR5 receptor.
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Affiliation(s)
- Pierre Calmet
- Max Planck Institute for the Science of Light, Erlangen, Germany.,Friedrich Alexander University (FAU) Erlangen-Nürnberg, Erlangen, Germany.,Chemistry and Biology of Membranes and Nanoobjects, UMR 5248 CNRS, University of Bordeaux, Bat. B14 allée Geoffroy St. Hilaire, 33600 Pessac, France
| | - Monica De Maria
- Department of Developmental Biology, Friedrich Alexander University of Erlangen-Nürnberg, Erlangen, Germany
| | - Etienne Harté
- Chemistry and Biology of Membranes and Nanoobjects, UMR 5248 CNRS, University of Bordeaux, Bat. B14 allée Geoffroy St. Hilaire, 33600 Pessac, France
| | - Daniel Lamb
- Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK
| | - Maria Serrano-Vega
- Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK
| | - Ali Jazayeri
- Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK
| | - Nuska Tschammer
- Department of Developmental Biology, Friedrich Alexander University of Erlangen-Nürnberg, Erlangen, Germany.,NanoTemper Technologies GmbH, Munich, Germany
| | - Isabel D Alves
- Chemistry and Biology of Membranes and Nanoobjects, UMR 5248 CNRS, University of Bordeaux, Bat. B14 allée Geoffroy St. Hilaire, 33600 Pessac, France
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16
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Abstract
Preparation and storage of functional membrane proteins such as G-protein-coupled receptors (GPCRs) are crucial to the processes of drug delivery and discovery. Here, we describe a method of preparing powdered GPCRs using rhodopsin as the prototype. We purified rhodopsin in CHAPS detergent with low detergent to protein ratio so the bulk of the sample represented protein (ca. 72% w/w). Our new method for generating powders of membrane proteins followed by rehydration paves the way for conducting functional and biophysical experiments. As an illustrative application, powdered rhodopsin was prepared with and without the cofactor 11-cis-retinal to enable partial rehydration of the protein with D2O in a controlled manner. Quasi-elastic neutron scattering studies using both spatial motion and energy landscape models form the basis for crucial insights into structural fluctuations and thermodynamics of GPCR activation.
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Affiliation(s)
| | - Udeep Chawla
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Michael F. Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
- Department of Physics, University of Arizona, Tucson, AZ 85721, USA
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17
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Shrestha UR, Perera SMDC, Bhowmik D, Chawla U, Mamontov E, Brown MF, Chu XQ. Quasi-elastic Neutron Scattering Reveals Ligand-Induced Protein Dynamics of a G-Protein-Coupled Receptor. J Phys Chem Lett 2016; 7:4130-4136. [PMID: 27628201 PMCID: PMC5378701 DOI: 10.1021/acs.jpclett.6b01632] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Light activation of the visual G-protein-coupled receptor (GPCR) rhodopsin leads to significant structural fluctuations of the protein embedded within the membrane yielding the activation of cognate G-protein (transducin), which initiates biological signaling. Here, we report a quasi-elastic neutron scattering study of the activation of rhodopsin as a GPCR prototype. Our results reveal a broadly distributed relaxation of hydrogen atom dynamics of rhodopsin on a picosecond-nanosecond time scale, crucial for protein function, as only observed for globular proteins previously. Interestingly, the results suggest significant differences in the intrinsic protein dynamics of the dark-state rhodopsin versus the ligand-free apoprotein, opsin. These differences can be attributed to the influence of the covalently bound retinal ligand. Furthermore, an idea of the generic free-energy landscape is used to explain the GPCR dynamics of ligand-binding and ligand-free protein conformations, which can be further applied to other GPCR systems.
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Affiliation(s)
- Utsab R. Shrestha
- Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201, USA
| | | | - Debsindhu Bhowmik
- Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201, USA
| | - Udeep Chawla
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Eugene Mamontov
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Michael F. Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
- Department of Physics, University of Arizona, Tucson, AZ 85721, USA
| | - Xiang-qiang Chu
- Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201, USA
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