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Schafer CT, Pauszek RF, Gustavsson M, Handel TM, Millar DP. Distinct Activation Mechanisms of CXCR4 and ACKR3 Revealed by Single-Molecule Analysis of their Conformational Landscapes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.10.31.564925. [PMID: 37961571 PMCID: PMC10635023 DOI: 10.1101/2023.10.31.564925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
The canonical chemokine receptor CXCR4 and atypical receptor ACKR3 both respond to CXCL12 but induce different effector responses to regulate cell migration. While CXCR4 couples to G proteins and directly promotes cell migration, ACKR3 is G protein-independent and scavenges CXCL12 to regulate extracellular chemokine levels and maintain CXCR4 responsiveness, thereby indirectly influencing migration. The receptors also have distinct activation requirements. CXCR4 only responds to wild-type CXCL12 and is sensitive to mutation of the chemokine. By contrast, ACKR3 recruits GPCR kinases (GRKs) and β-arrestins and promiscuously responds to CXCL12, CXCL12 variants, other peptides and proteins, and is relatively insensitive to mutation. To investigate the role of conformational dynamics in the distinct pharmacological behaviors of CXCR4 and ACKR3, we employed single-molecule FRET to track discrete conformational states of the receptors in real-time. The data revealed that apo-CXCR4 preferentially populates a high-FRET inactive state, while apo-ACKR3 shows little conformational preference and high transition probabilities among multiple inactive, intermediate and active conformations, consistent with its propensity for activation. Multiple active-like ACKR3 conformations are populated in response to agonists, compared to the single CXCR4 active-state. This and the markedly different conformational landscapes of the receptors suggest that activation of ACKR3 may be achieved by a broader distribution of conformational states than CXCR4. Much of the conformational heterogeneity of ACKR3 is linked to a single residue that differs between ACKR3 and CXCR4. The dynamic properties of ACKR3 may underly its inability to form productive interactions with G proteins that would drive canonical GPCR signaling.
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Affiliation(s)
- Christopher T. Schafer
- Skaggs School of Pharmacy and Pharmaceutical Sciences, Department of Pharmacology, University of California San Diego, La Jolla, CA 92037
| | - Raymond F. Pauszek
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037
| | - Martin Gustavsson
- Skaggs School of Pharmacy and Pharmaceutical Sciences, Department of Pharmacology, University of California San Diego, La Jolla, CA 92037
| | - Tracy M. Handel
- Skaggs School of Pharmacy and Pharmaceutical Sciences, Department of Pharmacology, University of California San Diego, La Jolla, CA 92037
| | - David P. Millar
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037
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2
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Shumate AD, Farrens DL. A rapid, tag-free way to purify functional GPCRs. J Biol Chem 2024; 300:105558. [PMID: 38097184 PMCID: PMC10820827 DOI: 10.1016/j.jbc.2023.105558] [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: 05/12/2023] [Revised: 12/01/2023] [Accepted: 12/05/2023] [Indexed: 01/14/2024] Open
Abstract
G protein-coupled receptors (GPCRs) play diverse signaling roles and represent major pharmaceutical targets. Consequently, they are the focus of intense study, and numerous advances have been made in their handling and analysis. However, a universal way to purify GPCRs has remained elusive, in part because of their inherent instability when isolated from cells. To address this, we have developed a general, rapid, and tag-free way to purify GPCRs. The method uses short peptide analogs of the Gα subunit C terminus (Gα-CT) that are attached to chromatography beads (Gα-CT resin). Because the Gα-CT peptides bind active GPCRs with high affinity, the Gα-CT resin selectively purifies only active functional receptors. We use this method to purify both rhodopsin and the β2-adrenergic receptor and show they can be purified in either active conformations or inactive conformations, simply by varying elution conditions. While simple in concept-leveraging the conserved GPCR-Gα-CT binding interaction for the purpose of GPCR purification-we think this approach holds excellent potential to isolate functional receptors for a myriad of uses, from structural biology to proteomics.
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Affiliation(s)
- Anthony D Shumate
- Department of Chemical Biology and Physiology, Oregon Health and Science University, Portland, Oregon, USA
| | - David L Farrens
- Department of Chemical Biology and Physiology, Oregon Health and Science University, Portland, Oregon, USA.
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3
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Castiglione GM, Chiu YLI, Gutierrez EDA, Van Nynatten A, Hauser FE, Preston M, Bhattacharyya N, Schott RK, Chang BSW. Convergent evolution of dim light vision in owls and deep-diving whales. Curr Biol 2023; 33:4733-4740.e4. [PMID: 37776863 DOI: 10.1016/j.cub.2023.09.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Revised: 08/21/2023] [Accepted: 09/05/2023] [Indexed: 10/02/2023]
Abstract
Animals with enhanced dim-light sensitivity are at higher risk of light-induced retinal degeneration when exposed to bright light conditions.1,2,3,4 This trade-off is mediated by the rod photoreceptor sensory protein, rhodopsin (RHO), and its toxic vitamin A chromophore by-product, all-trans retinal.5,6,7,8 Rod arrestin (Arr-1) binds to RHO and promotes sequestration of excess all-trans retinal,9,10 which has recently been suggested as a protective mechanism against photoreceptor cell death.2,11 We investigated Arr-1 evolution in animals at high risk of retinal damage due to periodic bright-light exposure of rod-dominated retinas. Here, we find the convergent evolution of enhanced Arr-1/RHO all-trans-retinal sequestration in owls and deep-diving whales. Statistical analyses reveal a parallel acceleration of Arr-1 evolutionary rates in these lineages, which is associated with the introduction of a rare Arr-1 mutation (Q69R) into the RHO-Arr-1 binding interface. Using in vitro assays, we find that this single mutation significantly enhances RHO-all-trans-retinal sequestration by ∼30%. This functional convergence across 300 million years of evolutionary divergence suggests that Arr-1 and RHO may play an underappreciated role in the photoprotection of the eye, with potentially vast clinical significance.
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Affiliation(s)
- Gianni M Castiglione
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA; Department of Ophthalmology & Visual Sciences, Vanderbilt University, Nashville, TN 37232, USA; Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada; Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada; Evolutionary Studies, Vanderbilt University, Nashville, TN 37235, USA.
| | - Yan L I Chiu
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Eduardo de A Gutierrez
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
| | - Alexander Van Nynatten
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada; Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada
| | - Frances E Hauser
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada; Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada
| | - Matthew Preston
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Nihar Bhattacharyya
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada; Institute of Ophthalmology, University College London, London EC1V 2PD, UK
| | - Ryan K Schott
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada; Department of Biology and Centre for Vision Research, York University, Toronto, ON M3J 1P3, Canada; Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
| | - Belinda S W Chang
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada; Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada.
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4
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Hong JD, Palczewski K. A short story on how chromophore is hydrolyzed from rhodopsin for recycling. Bioessays 2023; 45:e2300068. [PMID: 37454357 PMCID: PMC10614701 DOI: 10.1002/bies.202300068] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 05/24/2023] [Accepted: 05/30/2023] [Indexed: 07/18/2023]
Abstract
The photocycle of visual opsins is essential to maintain the light sensitivity of the retina. The early physical observations of the rhodopsin photocycle by Böll and Kühne in the 1870s inspired over a century's worth of investigations on rhodopsin biochemistry. A single photon isomerizes the Schiff-base linked 11-cis-retinylidene chromophore of rhodopsin, converting it to the all-trans agonist to elicit phototransduction through photoactivated rhodopsin (Rho*). Schiff base hydrolysis of the agonist is a key step in the photocycle, not only diminishing ongoing phototransduction but also allowing for entry and binding of fresh 11-cis chromophore to regenerate the rhodopsin pigment and maintain light sensitivity. Many challenges have been encountered in measuring the rate of this hydrolysis, but recent advancements have facilitated studies of the hydrolysis within the native membrane environment of rhodopsin. These techniques can now be applied to study hydrolysis of agonist in other opsin proteins that mediate phototransduction or chromophore turnover. In this review, we discuss the progress that has been made in characterizing the rhodopsin photocycle and the journey to characterize the hydrolysis of its all-trans-retinylidene agonist.
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Affiliation(s)
- John D. Hong
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California Irvine, Irvine, CA 92697, USA
- Department of Chemistry, University of California Irvine, Irvine, CA 92697, USA
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California Irvine, Irvine, CA 92697, USA
- Department of Chemistry, University of California Irvine, Irvine, CA 92697, USA
- Department of Physiology and Biophysics, University of California Irvine, Irvine, CA 92697, USA
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA 92697, USA
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Sadee W. Ligand-Free Signaling of G-Protein-Coupled Receptors: Physiology, Pharmacology, and Genetics. Molecules 2023; 28:6375. [PMID: 37687205 PMCID: PMC10489045 DOI: 10.3390/molecules28176375] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 08/28/2023] [Accepted: 08/30/2023] [Indexed: 09/10/2023] Open
Abstract
G-protein-coupled receptors (GPCRs) are ubiquitous sensors and regulators of cellular functions. Each GPCR exists in complex aggregates with multiple resting and active conformations. Designed to detect weak stimuli, GPCRs can also activate spontaneously, resulting in basal ligand-free signaling. Agonists trigger a cascade of events leading to an activated agonist-receptor G-protein complex with high agonist affinity. However, the ensuing signaling process can further remodel the receptor complex to reduce agonist affinity, causing rapid ligand dissociation. The acutely activated ligand-free receptor can continue signaling, as proposed for rhodopsin and μ opioid receptors, resulting in robust receptor activation at low agonist occupancy with enhanced agonist potency. Continued receptor stimulation can further modify the receptor complex, regulating sustained ligand-free signaling-proposed to play a role in opioid dependence. Basal, acutely agonist-triggered, and sustained elevated ligand-free signaling could each have distinct functions, reflecting multi-state conformations of GPCRs. This review addresses basal and stimulus-activated ligand-free signaling, its regulation, genetic factors, and pharmacological implications, focusing on opioid and serotonin receptors, and the growth hormone secretagogue receptor (GHSR). The hypothesis is proposed that ligand-free signaling of 5-HT2A receptors mediate therapeutic effects of psychedelic drugs. Research avenues are suggested to close the gaps in our knowledge of ligand-free GPCR signaling.
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Affiliation(s)
- Wolfgang Sadee
- Cancer Biology and Genetics, College of Medicine, The Ohio State University, Columbus, OH 43210, USA;
- Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA
- Aether Therapeutics Inc., Austin, TX 78756, USA
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6
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Hofmann KP, Lamb TD. Rhodopsin, light-sensor of vision. Prog Retin Eye Res 2023; 93:101116. [PMID: 36273969 DOI: 10.1016/j.preteyeres.2022.101116] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Revised: 08/20/2022] [Accepted: 08/22/2022] [Indexed: 11/06/2022]
Abstract
The light sensor of vertebrate scotopic (low-light) vision, rhodopsin, is a G-protein-coupled receptor comprising a polypeptide chain with bound chromophore, 11-cis-retinal, that exhibits remarkable physicochemical properties. This photopigment is extremely stable in the dark, yet its chromophore isomerises upon photon absorption with 70% efficiency, enabling the activation of its G-protein, transducin, with high efficiency. Rhodopsin's photochemical and biochemical activities occur over very different time-scales: the energy of retinaldehyde's excited state is stored in <1 ps in retinal-protein interactions, but it takes milliseconds for the catalytically active state to form, and many tens of minutes for the resting state to be restored. In this review, we describe the properties of rhodopsin and its role in rod phototransduction. We first introduce rhodopsin's gross structural features, its evolution, and the basic mechanisms of its activation. We then discuss light absorption and spectral sensitivity, photoreceptor electrical responses that result from the activity of individual rhodopsin molecules, and recovery of rhodopsin and the visual system from intense bleaching exposures. We then provide a detailed examination of rhodopsin's molecular structure and function, first in its dark state, and then in the active Meta states that govern its interactions with transducin, rhodopsin kinase and arrestin. While it is clear that rhodopsin's molecular properties are exquisitely honed for phototransduction, from starlight to dawn/dusk intensity levels, our understanding of how its molecular interactions determine the properties of scotopic vision remains incomplete. We describe potential future directions of research, and outline several major problems that remain to be solved.
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Affiliation(s)
- Klaus Peter Hofmann
- Institut für Medizinische Physik und Biophysik (CC2), Charité, and, Zentrum für Biophysik und Bioinformatik, Humboldt-Unversität zu Berlin, Berlin, 10117, Germany.
| | - Trevor D Lamb
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, The Australian National University, Canberra, ACT 2600, Australia.
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7
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Ligand-Free Signaling of G-Protein-Coupled Receptors: Relevance to μ Opioid Receptors in Analgesia and Addiction. Molecules 2022; 27:molecules27185826. [PMID: 36144565 PMCID: PMC9503102 DOI: 10.3390/molecules27185826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 09/04/2022] [Accepted: 09/06/2022] [Indexed: 11/17/2022] Open
Abstract
Numerous G-protein-coupled receptors (GPCRs) display ligand-free basal signaling with potential physiological functions, a target in drug development. As an example, the μ opioid receptor (MOR) signals in ligand-free form (MOR-μ*), influencing opioid responses. In addition, agonists bind to MOR but can dissociate upon MOR activation, with ligand-free MOR-μ* carrying out signaling. Opioid pain therapy is effective but incurs adverse effects (ADRs) and risk of opioid use disorder (OUD). Sustained opioid agonist exposure increases persistent basal MOR-μ* activity, which could be a driving force for OUD and ADRs. Antagonists competitively prevent resting MOR (MOR-μ) activation to MOR-μ*, while common antagonists, such as naloxone and naltrexone, also bind to and block ligand-free MOR-μ*, acting as potent inverse agonists. A neutral antagonist, 6β-naltrexol (6BN), binds to but does not block MOR-μ*, preventing MOR-μ activation only competitively with reduced potency. We hypothesize that 6BN gradually accelerates MOR-μ* reversal to resting-state MOR-μ. Thus, 6BN potently prevents opioid dependence in rodents, at doses well below those blocking antinociception or causing withdrawal. Acting as a ‘retrograde addiction modulator’, 6BN could represent a novel class of therapeutics for OUD. Further studies need to address regulation of MOR-μ* and, more broadly, the physiological and pharmacological significance of ligand-free signaling in GPCRs.
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8
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Tian H, Gunnison KM, Kazmi MA, Sakmar TP, Huber T. FRET sensors reveal the retinal entry pathway in the G protein-coupled receptor rhodopsin. iScience 2022; 25:104060. [PMID: 35355518 PMCID: PMC8958324 DOI: 10.1016/j.isci.2022.104060] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 01/11/2022] [Accepted: 03/04/2022] [Indexed: 11/26/2022] Open
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9
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Kinetic model of GPCR-G protein interactions reveals allokairic modulation of signaling. Nat Commun 2022; 13:1202. [PMID: 35260563 PMCID: PMC8904551 DOI: 10.1038/s41467-022-28789-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Accepted: 02/09/2022] [Indexed: 11/23/2022] Open
Abstract
Established models of ternary complex formation between hormone, G protein coupled receptor (GPCR), and G protein assume that all interactions occur under equilibrium conditions. However, recent studies have established that the lifetimes of these interactions are comparable to the duration of hormone activated GPCR signaling. To simulate interactions during such non-equilibrium conditions, we propose a kinetic model wherein the receptor undergoes rate-limiting transitions between two hormone-bound active states. Simulations, using experimentally measured parameters, demonstrate transient states in ternary complex formation, and delineate the phenomenon of GPCR priming, wherein non-cognate G proteins substantially enhance cognate G protein signaling. Our model reveals that kinetic barriers of slow receptor interconversion can be overcome through allokairic modulation, a regulatory mechanism of ternary complex formation and downstream signaling. Experimentally validated kinetic simulations uncover transient enhancement of GPCR ternary complex formation by allokairic effectors.
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10
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Schafer CT, Shumate A, Farrens DL. Novel fluorescent GPCR biosensor detects retinal equilibrium binding to opsin and active G protein and arrestin signaling conformations. J Biol Chem 2020; 295:17486-17496. [PMID: 33453993 DOI: 10.1074/jbc.ra120.014631] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 09/25/2020] [Indexed: 01/14/2023] Open
Abstract
Rhodopsin is a canonical class A photosensitive G protein-coupled receptor (GPCR), yet relatively few pharmaceutical agents targeting this visual receptor have been identified, in part due to the unique characteristics of its light-sensitive, covalently bound retinal ligands. Rhodopsin becomes activated when light isomerizes 11-cis-retinal into an agonist, all-trans-retinal (ATR), which enables the receptor to activate its G protein. We have previously demonstrated that, despite being covalently bound, ATR can display properties of equilibrium binding, yet how this is accomplished is unknown. Here, we describe a new approach for both identifying compounds that can activate and attenuate rhodopsin and testing the hypothesis that opsin binds retinal in equilibrium. Our method uses opsin-based fluorescent sensors, which directly report the formation of active receptor conformations by detecting the binding of G protein or arrestin fragments that have been fused onto the receptor's C terminus. We show that these biosensors can be used to monitor equilibrium binding of the agonist, ATR, as well as the noncovalent binding of β-ionone, an antagonist for G protein activation. Finally, we use these novel biosensors to observe ATR release from an activated, unlabeled receptor and its subsequent transfer to the sensor in real time. Taken together, these data support the retinal equilibrium binding hypothesis. The approach we describe should prove directly translatable to other GPCRs, providing a new tool for ligand discovery and mutant characterization.
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Affiliation(s)
- Christopher T Schafer
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, Oregon, USA
| | - Anthony Shumate
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, Oregon, USA
| | - David L Farrens
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, Oregon, USA.
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11
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Accelerated evolution and positive selection of rhodopsin in Tibetan loaches living in high altitude. Int J Biol Macromol 2020; 165:2598-2606. [PMID: 33470199 DOI: 10.1016/j.ijbiomac.2020.10.151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 10/16/2020] [Accepted: 10/19/2020] [Indexed: 11/22/2022]
Abstract
Rhodopsin (RH1), the temperature-sensitive visual pigment, attained cold adaptation by functional trade-offs between protein stability and activity. Recent studies suggested convergent selection pressures drove cold adaptation of rhodopsin in high altitude catfishes through nonparallel molecular mechanisms. Here, we tested whether the similar shift occurred in RH1 of Tibetan loaches on the Qinghai-Tibet Plateau (QTP) by investigating the molecular evolution and potential effect on function of RH1. We sequenced RH1 from 27 Triplophysa species, and four lowland loaches and combined these data with published sequences. Tests using a series of models of molecular evolution resulted in strong evidence for accelerated evolution and positive selection in Triplophysa RH1. Three positively selected sites were near key functional domains modulating nonspectral properties of rhodopsin, substitutions of which were likely to compensate for cold-induced decrease in rhodopsin kinetics in cold environments. Moreover, although accelerated evolutionary rates in Tibetan loaches was convergent with those in high altitude catfishes, the sites under positive selection were nonoverlapping. Our findings provide evidence for convergent shift in selection pressures of RH1 in high altitude fish during the ecological transition to cold environment of the QTP.
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12
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Hilger D, Kumar KK, Hu H, Pedersen MF, O'Brien ES, Giehm L, Jennings C, Eskici G, Inoue A, Lerch M, Mathiesen JM, Skiniotis G, Kobilka BK. Structural insights into differences in G protein activation by family A and family B GPCRs. Science 2020; 369:369/6503/eaba3373. [PMID: 32732395 DOI: 10.1126/science.aba3373] [Citation(s) in RCA: 84] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 06/17/2020] [Indexed: 01/06/2023]
Abstract
Family B heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) play important roles in carbohydrate metabolism. Recent structures of family B GPCR-Gs protein complexes reveal a disruption in the α-helix of transmembrane segment 6 (TM6) not observed in family A GPCRs. To investigate the functional impact of this structural difference, we compared the structure and function of the glucagon receptor (GCGR; family B) with the β2 adrenergic receptor (β2AR; family A). We determined the structure of the GCGR-Gs complex by means of cryo-electron microscopy at 3.1-angstrom resolution. This structure shows the distinct break in TM6. Guanosine triphosphate (GTP) turnover, guanosine diphosphate release, GTP binding, and G protein dissociation studies revealed much slower rates for G protein activation by the GCGR compared with the β2AR. Fluorescence and double electron-electron resonance studies suggest that this difference is due to the inability of agonist alone to induce a detectable outward movement of the cytoplasmic end of TM6.
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Affiliation(s)
- Daniel Hilger
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA
| | - Kaavya Krishna Kumar
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA
| | - Hongli Hu
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA.,Department of Structural Biology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA
| | | | - Evan S O'Brien
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA
| | - Lise Giehm
- Zealand Pharma A/S, Sydmarken 11, Søborg 2860, Denmark
| | - Christine Jennings
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Gözde Eskici
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA.,Department of Structural Biology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA
| | - Asuka Inoue
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Michael Lerch
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | | | - Georgios Skiniotis
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA. .,Department of Structural Biology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA.,Department of Photon Science, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Brian K Kobilka
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA.
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13
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Gupte TM, Ritt M, Dysthe M, Malik RU, Sivaramakrishnan S. Minute-scale persistence of a GPCR conformation state triggered by non-cognate G protein interactions primes signaling. Nat Commun 2019; 10:4836. [PMID: 31645561 PMCID: PMC6811539 DOI: 10.1038/s41467-019-12755-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 09/17/2019] [Indexed: 02/01/2023] Open
Abstract
Despite the crowded nature of the cellular milieu, ligand-GPCR-G protein interactions are traditionally viewed as spatially and temporally isolated events. In contrast, recent reports suggest the spatial and temporal coupling of receptor-effector interactions, with the potential to diversify downstream responses. In this study, we combine protein engineering of GPCR-G protein interactions with affinity sequestration and photo-manipulation of the crucial Gα C terminus, to demonstrate the temporal coupling of cognate and non-cognate G protein interactions through priming of the GPCR conformation. We find that interactions of the Gαs and Gαq C termini with the β2-adrenergic receptor (β2-AR), targeted at the G-protein-binding site, enhance Gs activation and cyclic AMP levels. β2-AR-Gα C termini interactions alter receptor conformation, which persists for ~90 s following Gα C terminus dissociation. Non-cognate G-protein expression levels impact cognate signaling in cells. Our study demonstrates temporal allostery in GPCRs, with implications for the modulation of downstream responses through the canonical G-protein-binding interface.
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Affiliation(s)
- Tejas M Gupte
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Twin-Cities, Minneapolis, Minnesota, 55455, USA
| | - Michael Ritt
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Twin-Cities, Minneapolis, Minnesota, 55455, USA
| | - Matthew Dysthe
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Twin-Cities, Minneapolis, Minnesota, 55455, USA
| | - Rabia U Malik
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Twin-Cities, Minneapolis, Minnesota, 55455, USA
| | - Sivaraj Sivaramakrishnan
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Twin-Cities, Minneapolis, Minnesota, 55455, USA.
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14
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Zhao P, Furness SGB. The nature of efficacy at G protein-coupled receptors. Biochem Pharmacol 2019; 170:113647. [PMID: 31585071 DOI: 10.1016/j.bcp.2019.113647] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 09/27/2019] [Indexed: 12/31/2022]
Abstract
G protein-coupled receptors (GPCRs) participate in many pathophysiological processes as well as almost all aspects of normal physiology. They are present at the surface of all cell types making them amenable and attractive targets for pharmaceutical therapeutics. GPCRs possess complex pharmacology with the ability to be turned on to various extents, have their constitutive activity suppressed and even switch between signaling pathways to which they couple. Underlying this complex pharmacology is GPCR signaling efficacy, and differences in efficacy promoted by alternative ligands and in different tissues is of great interest to biology in general and also the pharmaceutical industry. In this review we hope to discuss what the molecular foundations of efficacy are and whether a new approach utilizing a rate-dependent model may provide new insights into this phenomenon.
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Affiliation(s)
- Peishen Zhao
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria 3052, Australia.
| | - Sebastian G B Furness
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria 3052, Australia.
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15
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Draper-Joyce C, Furness SGB. Conformational Transitions and the Activation of Heterotrimeric G Proteins by G Protein-Coupled Receptors. ACS Pharmacol Transl Sci 2019; 2:285-290. [PMID: 32259062 PMCID: PMC7088962 DOI: 10.1021/acsptsci.9b00054] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Indexed: 01/10/2023]
Abstract
G protein-coupled receptors (GPCRs) are particularly attractive targets for therapeutic pharmaceuticals. This is because they are involved in almost all facets of physiology, in many pathophysiological processes, they are tractable due to their cell surface location, and can exhibit highly textured pharmacology. While the development of new drugs does not require the molecular details of the mechanism of activity for a particular target, there has been increasing interest in the GPCR field in these details. In part, this has come with the recognition that differential activity at a particular target might be a way in which to leverage drug activity, either through manipulation of efficacy or through differential coupling (signaling bias). To this end, the past few years have seen a number of publications that have specifically attempted to address one or more aspects of the molecular reaction pathway, leading to activation of heterotrimeric G proteins by GPCRs.
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16
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Gutierrez EDA, Castiglione GM, Morrow JM, Schott RK, Loureiro LO, Lim BK, Chang BSW. Functional Shifts in Bat Dim-Light Visual Pigment Are Associated with Differing Echolocation Abilities and Reveal Molecular Adaptation to Photic-Limited Environments. Mol Biol Evol 2019; 35:2422-2434. [PMID: 30010964 DOI: 10.1093/molbev/msy140] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Bats are excellent models for studying the molecular basis of sensory adaptation. In Chiroptera, a sensory trade-off has been proposed between the visual and auditory systems, though the extent of this association has yet to be fully examined. To investigate whether variation in visual performance is associated with echolocation, we experimentally assayed the dim-light visual pigment rhodopsin from bat species with differing echolocation abilities. While spectral tuning properties were similar among bats, we found that the rate of decay of their light-activated state was significantly slower in a nonecholocating bat relative to species that use distinct echolocation strategies, consistent with a sensory trade-off hypothesis. We also found that these rates of decay were remarkably slower compared with those of other mammals, likely indicating an adaptation to dim light. To examine whether functional changes in rhodopsin are associated with shifts in selection intensity upon bat Rh1 sequences, we implemented selection analyses using codon-based likelihood clade models. While no shifts in selection were identified in response to diverse echolocation abilities of bats, we detected a significant increase in the intensity of evolutionary constraint accompanying the diversification of Chiroptera. Taken together, this suggests that substitutions that modulate the stability of the light-activated rhodopsin state were likely maintained through intensified constraint after bats diversified, being finely tuned in response to novel sensory specializations. Our study demonstrates the power of combining experimental and computational approaches for investigating functional mechanisms underlying the evolution of complex sensory adaptations.
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Affiliation(s)
- Eduardo de A Gutierrez
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
| | - Gianni M Castiglione
- Department of Cell and Systems Biology, University of Toronto, ON, Canada.,Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - James M Morrow
- Department of Cell and Systems Biology, University of Toronto, ON, Canada.,Centre of Forensic Sciences, Toronto, ON, Canada
| | - Ryan K Schott
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada.,Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
| | - Livia O Loureiro
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
| | - Burton K Lim
- Department of Natural History, Royal Ontario Museum, Toronto, ON, Canada
| | - Belinda S W Chang
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada.,Department of Cell and Systems Biology, University of Toronto, ON, Canada.,Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, ON, Canada
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17
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Senapati S, Poma AB, Cieplak M, Filipek S, Park PSH. Differentiating between Inactive and Active States of Rhodopsin by Atomic Force Microscopy in Native Membranes. Anal Chem 2019; 91:7226-7235. [PMID: 31074606 DOI: 10.1021/acs.analchem.9b00546] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Membrane proteins, including G protein-coupled receptors (GPCRs), present a challenge in studying their structural properties under physiological conditions. Moreover, to better understand the activity of proteins requires examination of single molecule behaviors rather than ensemble averaged behaviors. Force-distance curve-based AFM (FD-AFM) was utilized to directly probe and localize the conformational states of a GPCR within the membrane at nanoscale resolution based on the mechanical properties of the receptor. FD-AFM was applied to rhodopsin, the light receptor and a prototypical GPCR, embedded in native rod outer segment disc membranes from photoreceptor cells of the retina in mice. Both FD-AFM and computational studies on coarse-grained models of rhodopsin revealed that the active state of the receptor has a higher Young's modulus compared to the inactive state of the receptor. Thus, the inactive and active states of rhodopsin could be differentiated based on the stiffness of the receptor. Differentiating the states based on the Young's modulus allowed for the mapping of the different states within the membrane. Quantifying the active states present in the membrane containing the constitutively active G90D rhodopsin mutant or apoprotein opsin revealed that most receptors adopt an active state. Traditionally, constitutive activity of GPCRs has been described in terms of two-state models where the receptor can achieve only a single active state. FD-AFM data are inconsistent with a two-state model but instead require models that incorporate multiple active states.
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Affiliation(s)
- Subhadip Senapati
- Department of Ophthalmology and Visual Sciences , Case Western Reserve University , Cleveland , Ohio 44106 , United States
| | - Adolfo B Poma
- Institute of Fundamental Technological Research , Polish Academy of Sciences , Pawińskiego 5B , 02-106 Warsaw , Poland.,Institute of Physics , Polish Academy of Sciences , Aleja Lotników 32/46 , 02-668 Warsaw , Poland
| | - Marek Cieplak
- Institute of Physics , Polish Academy of Sciences , Aleja Lotników 32/46 , 02-668 Warsaw , Poland
| | - Sławomir Filipek
- Faculty of Chemistry, Biological and Chemical Research Centre , University of Warsaw , 02-093 Warsaw , Poland
| | - Paul S H Park
- Department of Ophthalmology and Visual Sciences , Case Western Reserve University , Cleveland , Ohio 44106 , United States
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18
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Apo-Opsin Exists in Equilibrium Between a Predominant Inactive and a Rare Highly Active State. J Neurosci 2018; 39:212-223. [PMID: 30459230 DOI: 10.1523/jneurosci.1980-18.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 10/30/2018] [Accepted: 11/04/2018] [Indexed: 12/17/2022] Open
Abstract
Bleaching adaptation in rod photoreceptors is mediated by apo-opsin, which activates phototransduction with effective activity 105- to 106-fold lower than that of photoactivated rhodopsin (meta II). However, the mechanism that produces such low opsin activity is unknown. To address this question, we sought to record single opsin responses in mouse rods. We used mutant mice lacking efficient calcium feedback to boosts rod responses and generated a small fraction of opsin by photobleaching ∼1% of rhodopsin. The bleach produced a dramatic increase in the frequency of discrete photoresponse-like events. This activity persisted for hours, was quenched by 11-cis-retinal, and was blocked by uncoupling opsin from phototransduction, all indicating opsin as its source. Opsin-driven discrete activity was also observed in rods containing non-activatable rhodopsin, ruling out transactivation of rhodopsin by opsin. We conclude that bleaching adaptation is mediated by opsin that exists in equilibrium between a predominant inactive and a rare meta II-like state.SIGNIFICANCE STATEMENT Electrophysiological analysis is used to show that the G-protein-coupled receptor opsin exists in equilibrium between a predominant inactive and a rare highly active state that mediates bleaching adaptation in photoreceptors.
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19
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Masureel M, Zou Y, Picard LP, van der Westhuizen E, Mahoney JP, Rodrigues JPGLM, Mildorf TJ, Dror RO, Shaw DE, Bouvier M, Pardon E, Steyaert J, Sunahara RK, Weis WI, Zhang C, Kobilka BK. Structural insights into binding specificity, efficacy and bias of a β 2AR partial agonist. Nat Chem Biol 2018; 14:1059-1066. [PMID: 30327561 PMCID: PMC6197491 DOI: 10.1038/s41589-018-0145-x] [Citation(s) in RCA: 124] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 09/06/2018] [Indexed: 11/08/2022]
Abstract
Salmeterol is a partial agonist for the β2 adrenergic receptor (β2AR) and the first long-acting β2AR agonist to be widely used clinically for the treatment of asthma and chronic obstructive pulmonary disease. Salmeterol's safety and mechanism of action have both been controversial. To understand its unusual pharmacological action and partial agonism, we obtained the crystal structure of salmeterol-bound β2AR in complex with an active-state-stabilizing nanobody. The structure reveals the location of the salmeterol exosite, where sequence differences between β1AR and β2AR explain the high receptor-subtype selectivity. A structural comparison with the β2AR bound to the full agonist epinephrine reveals differences in the hydrogen-bond network involving residues Ser2045.43 and Asn2936.55. Mutagenesis and biophysical studies suggested that these interactions lead to a distinct active-state conformation that is responsible for the partial efficacy of G-protein activation and the limited β-arrestin recruitment for salmeterol.
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Affiliation(s)
- Matthieu Masureel
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Yaozhong Zou
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
- Geneus Technologies, Ltd, Chengdu, Sichuan, People's Republic of China
| | - Louis-Philippe Picard
- Department of Biochemistry, Institute for Research in Immunology and Cancer, Université de Montreal, Montreal, Québec, Canada
| | - Emma van der Westhuizen
- Department of Biochemistry, Institute for Research in Immunology and Cancer, Université de Montreal, Montreal, Québec, Canada
- Monash Institute for Pharmaceutical Sciences, Monash University, Victoria, Australia
| | - Jacob P Mahoney
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - João P G L M Rodrigues
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
- Department of Computer Science, Stanford University, Stanford, CA, USA
- Department of Structural Biology, Stanford University, Stanford, CA, USA
| | - Thomas J Mildorf
- D. E. Shaw Research, New York, NY, USA
- Dropbox, New York, NY, USA
| | - Ron O Dror
- D. E. Shaw Research, New York, NY, USA
- Department of Computer Science and Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA, USA
| | - David E Shaw
- D. E. Shaw Research, New York, NY, USA
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Michel Bouvier
- Department of Biochemistry, Institute for Research in Immunology and Cancer, Université de Montreal, Montreal, Québec, Canada
| | - Els Pardon
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium
- Structural Biology Research Center, VIB, Brussels, Belgium
| | - Jan Steyaert
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium
- Structural Biology Research Center, VIB, Brussels, Belgium
| | - Roger K Sunahara
- Department of Pharmacology, University of California San Diego School of Medicine, La Jolla, CA, USA
| | - William I Weis
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
- Department of Structural Biology, Stanford University, Stanford, CA, USA
| | - Cheng Zhang
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
| | - Brian K Kobilka
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.
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20
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Castiglione GM, Chang BS. Functional trade-offs and environmental variation shaped ancient trajectories in the evolution of dim-light vision. eLife 2018; 7:35957. [PMID: 30362942 PMCID: PMC6203435 DOI: 10.7554/elife.35957] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 09/09/2018] [Indexed: 12/11/2022] Open
Abstract
Trade-offs between protein stability and activity can restrict access to evolutionary trajectories, but widespread epistasis may facilitate indirect routes to adaptation. This may be enhanced by natural environmental variation, but in multicellular organisms this process is poorly understood. We investigated a paradoxical trajectory taken during the evolution of tetrapod dim-light vision, where in the rod visual pigment rhodopsin, E122 was fixed 350 million years ago, a residue associated with increased active-state (MII) stability but greatly diminished rod photosensitivity. Here, we demonstrate that high MII stability could have likely evolved without E122, but instead, selection appears to have entrenched E122 in tetrapods via epistatic interactions with nearby coevolving sites. In fishes by contrast, selection may have exploited these epistatic effects to explore alternative trajectories, but via indirect routes with low MII stability. Our results suggest that within tetrapods, E122 and high MII stability cannot be sacrificed-not even for improvements to rod photosensitivity.
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Affiliation(s)
- Gianni M Castiglione
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada.,Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
| | - Belinda Sw Chang
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada.,Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada.,Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Canada
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21
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Mattle D, Kuhn B, Aebi J, Bedoucha M, Kekilli D, Grozinger N, Alker A, Rudolph MG, Schmid G, Schertler GFX, Hennig M, Standfuss J, Dawson RJP. Ligand channel in pharmacologically stabilized rhodopsin. Proc Natl Acad Sci U S A 2018; 115:3640-3645. [PMID: 29555765 PMCID: PMC5889642 DOI: 10.1073/pnas.1718084115] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In the degenerative eye disease retinitis pigmentosa (RP), protein misfolding leads to fatal consequences for cell metabolism and rod and cone cell survival. To stop disease progression, a therapeutic approach focuses on stabilizing inherited protein mutants of the G protein-coupled receptor (GPCR) rhodopsin using pharmacological chaperones (PC) that improve receptor folding and trafficking. In this study, we discovered stabilizing nonretinal small molecules by virtual and thermofluor screening and determined the crystal structure of pharmacologically stabilized opsin at 2.4 Å resolution using one of the stabilizing hits (S-RS1). Chemical modification of S-RS1 and further structural analysis revealed the core binding motif of this class of rhodopsin stabilizers bound at the orthosteric binding site. Furthermore, previously unobserved conformational changes are visible at the intradiscal side of the seven-transmembrane helix bundle. A hallmark of this conformation is an open channel connecting the ligand binding site with the membrane and the intradiscal lumen of rod outer segments. Sufficient in size, the passage permits the exchange of hydrophobic ligands such as retinal. The results broaden our understanding of rhodopsin's conformational flexibility and enable therapeutic drug intervention against rhodopsin-related retinitis pigmentosa.
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Affiliation(s)
- Daniel Mattle
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland
- Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Bernd Kuhn
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland
| | - Johannes Aebi
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland
| | - Marc Bedoucha
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland
| | - Demet Kekilli
- Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Nathalie Grozinger
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland
| | - Andre Alker
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland
| | - Markus G Rudolph
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland
| | - Georg Schmid
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland
| | - Gebhard F X Schertler
- Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
- Department of Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Michael Hennig
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland
| | - Jörg Standfuss
- Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland;
| | - Roger J P Dawson
- Roche Pharma Research and Early Development, Therapeutic Modalities, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland;
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22
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Elgeti M, Kazmin R, Rose AS, Szczepek M, Hildebrand PW, Bartl FJ, Scheerer P, Hofmann KP. The arrestin-1 finger loop interacts with two distinct conformations of active rhodopsin. J Biol Chem 2018; 293:4403-4410. [PMID: 29363577 DOI: 10.1074/jbc.m117.817890] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 01/17/2018] [Indexed: 11/06/2022] Open
Abstract
Signaling of the prototypical G protein-coupled receptor (GPCR) rhodopsin through its cognate G protein transducin (Gt) is quenched when arrestin binds to the activated receptor. Although the overall architecture of the rhodopsin/arrestin complex is known, many questions regarding its specificity remain unresolved. Here, using FTIR difference spectroscopy and a dual pH/peptide titration assay, we show that rhodopsin maintains certain flexibility upon binding the "finger loop" of visual arrestin (prepared as synthetic peptide ArrFL-1). We found that two distinct complexes can be stabilized depending on the protonation state of E3.49 in the conserved (D)ERY motif. Both complexes exhibit different interaction modes and affinities of ArrFL-1 binding. The plasticity of the receptor within the rhodopsin/ArrFL-1 complex stands in contrast to the complex with the C terminus of the Gt α-subunit (GαCT), which stabilizes only one specific substate out of the conformational ensemble. However, Gt α-subunit binding and both ArrFL-1-binding modes involve a direct interaction to conserved R3.50, as determined by site-directed mutagenesis. Our findings highlight the importance of receptor conformational flexibility and cytoplasmic proton uptake for modulation of rhodopsin signaling and thereby extend the picture provided by crystal structures of the rhodopsin/arrestin and rhodopsin/ArrFL-1 complexes. Furthermore, the two binding modes of ArrFL-1 identified here involve motifs of conserved amino acids, which indicates that our results may have elucidated a common modulation mechanism of class A GPCR-G protein/-arrestin signaling.
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Affiliation(s)
- Matthias Elgeti
- From the Institut für Medizinische Physik und Biophysik (CC2), Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany,
| | - Roman Kazmin
- From the Institut für Medizinische Physik und Biophysik (CC2), Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Alexander S Rose
- From the Institut für Medizinische Physik und Biophysik (CC2), Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.,Group ProteInformatics
| | - Michal Szczepek
- From the Institut für Medizinische Physik und Biophysik (CC2), Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.,Group Protein X-ray Crystallography and Signal Transduction
| | - Peter W Hildebrand
- From the Institut für Medizinische Physik und Biophysik (CC2), Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.,Institut für Medizinische Physik und Biophysik, Universität Leipzig, Härtelstrasse 16-18, 04107 Leipzig, Germany
| | - Franz J Bartl
- From the Institut für Medizinische Physik und Biophysik (CC2), Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.,Institut für Biologie, Biophysikalische Chemie, Humboldt-Universität zu Berlin, Invalidenstrasse 42, 10115 Berlin, Germany
| | - Patrick Scheerer
- From the Institut für Medizinische Physik und Biophysik (CC2), Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.,Group Protein X-ray Crystallography and Signal Transduction
| | - Klaus Peter Hofmann
- From the Institut für Medizinische Physik und Biophysik (CC2), Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
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23
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Castiglione GM, Schott RK, Hauser FE, Chang BSW. Convergent selection pressures drive the evolution of rhodopsin kinetics at high altitudes via nonparallel mechanisms. Evolution 2018; 72:170-186. [DOI: 10.1111/evo.13396] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 11/02/2017] [Indexed: 01/01/2023]
Affiliation(s)
- Gianni M. Castiglione
- Department of Cell & Systems Biology; University of Toronto; Toronto Ontario M5S 3G5 Canada
- Department of Ecology & Evolutionary Biology; University of Toronto; Toronto Ontario M5S 3B2 Canada
| | - Ryan K. Schott
- Department of Ecology & Evolutionary Biology; University of Toronto; Toronto Ontario M5S 3B2 Canada
| | - Frances E. Hauser
- Department of Ecology & Evolutionary Biology; University of Toronto; Toronto Ontario M5S 3B2 Canada
| | - Belinda S. W. Chang
- Department of Cell & Systems Biology; University of Toronto; Toronto Ontario M5S 3G5 Canada
- Department of Ecology & Evolutionary Biology; University of Toronto; Toronto Ontario M5S 3B2 Canada
- Centre for the Analysis of Genome Evolution and Function; University of Toronto; Toronto Ontario M5S 3B2 Canada
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24
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Gebre ST, Cameron SA, Li L, Babu YS, Schramm VL. Intracellular rebinding of transition-state analogues provides extended in vivo inhibition lifetimes on human purine nucleoside phosphorylase. J Biol Chem 2017; 292:15907-15915. [PMID: 28794158 DOI: 10.1074/jbc.m117.801779] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 08/07/2017] [Indexed: 01/16/2023] Open
Abstract
Purine nucleoside phosphorylase (PNP) is part of the human purine salvage pathway. Its deficiency triggers apoptosis of activated T-cells, making it a target for T-cell proliferative disorders. Transition-state analogues of PNP bind with picomolar (pm) dissociation constants. Tight-binding PNP inhibitors show exceptionally long lifetimes on the target enzyme. We solve the mechanism of the target residence time by comparing functional off-rates in vitro and in vivo We report in vitro PNP-inhibitor dissociation rates (t½) from 3 to 31 min for seven Immucillins with dissociation constants of 115 to 6 pm Treatment of human erythrocytes with DADMe-Immucillin-H (DADMe-ImmH, 22 pm) causes complete inhibition of PNP. Loss of [14C]DADMe-ImmH from erythrocytes during multiple washes is slow and biphasic, resulting from inhibitor release and rebinding to PNP catalytic sites. The slow phase gave a t½ of 84 h. Loss of [14C]DADMe-ImmH from erythrocytes in the presence of excess unlabeled DADMe-ImmH increased to a t½ of 1.6 h by preventing rebinding. Thus, in human erythrocytes, rebinding of DADMe-ImmH is 50-fold more likely than diffusional loss of the inhibitor from the erythrocyte. Humans treated with a single oral dose of DADMe-ImmH in phase 1 clinical trials exhibit regain of PNP activity with a t½ of 59 days, corresponding to the erythropoiesis rate in humans. Thus, the PNP catalytic site recapture of DADMe-ImmH is highly favored in vivo We conclude that transition-state analogues with picomolar dissociation constants exhibit long lifetimes on their targets in vivo because the probability of the target enzyme recapturing inhibitor molecules is greater than diffusional loss to the extracellular space.
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Affiliation(s)
- Sara T Gebre
- From the Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461 and
| | - Scott A Cameron
- From the Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461 and
| | - Lei Li
- From the Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461 and
| | - Y S Babu
- BioCryst Pharmaceuticals, Inc., Birmingham, Alabama 35244
| | - Vern L Schramm
- From the Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461 and
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25
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Purification of Functional CB 1 and Analysis by Site-Directed Fluorescence Labeling Methods. Methods Enzymol 2017; 593:343-370. [PMID: 28750810 DOI: 10.1016/bs.mie.2017.06.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The human cannabinoid receptor, CB1, has been difficult to purify in a functional form, hampering structural and biophysical studies. Here, we present our approaches for obtaining pure, detergent solubilized, functional CB1. We also discuss our site-directed fluorescence labeling (SDFL) methods for identifying different structural changes that CB1 can undergo upon binding different cannabinoid ligands. To identify optimal CB1 constructs for these studies (those with the best expression levels, solubility in detergent and function), we first screened various CB1-green fluorescent protein chimeras in a mammalian expression system. Once identified, we then tagged the best candidates with the 1D4 epitope (the C-terminus of rhodopsin) and purified them using a single-step immunoaffinity process. The resulting, highly pure proteins retain their ability to activate G-protein, and are ~85% functional, as assessed by radioligand binding studies. The SDFL studies involve introducing single cysteine residues at key places in the receptor, then labeling them with a small fluorophore, bimane. The spectral properties of the bimane probe are then monitored before and after addition of cannabinoid ligands. Changes in fluorescence of the attached probe indicate regions of the receptor undergoing conformational changes upon ligand binding. Together, these approaches set the stage for a deeper understanding of the structure and function of CB1. Access to pure, functional CB1 makes subsequent structural studies possible (such as crystallography and single-particle EM analysis), and the SDFL studies enable a better structural and mechanistic understanding of this key receptor and the dynamic changes it undergoes during activation and attenuation.
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Alvarado C, Nachtigal D, Slack JP, Green BG. Differential modulation of the lactisole 'Sweet Water Taste' by sweeteners. PLoS One 2017; 12:e0180787. [PMID: 28700634 PMCID: PMC5507258 DOI: 10.1371/journal.pone.0180787] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 06/21/2017] [Indexed: 11/18/2022] Open
Abstract
Pre-exposure to taste stimuli and certain chemicals can cause water to have a taste. Here we studied further the 'sweet water taste' (SWT) perceived after exposure to the sweet taste inhibitor lactisole. Experiment 1 investigated an incidental observation that presenting lactisole in mixture with sucrose reduced the intensity of the SWT. The results confirmed this observation and also showed that rinsing with sucrose after lactisole could completely eliminate the SWT. The generalizability of these findings was investigated in experiment 2 by presenting 5 additional sweeteners before, during, or after exposure to lactisole. The results found with sucrose were replicated with fructose and cyclamate, but the 3 other sweeteners were less effective suppressors of the SWT, and the 2 sweeteners having the highest potency initially enhanced it. A third experiment investigated these interactions on the tongue tip and found that the lactisole SWT was perceived only when water was actively flowed across the tongue. The same experiment yielded evidence against the possibility that suppression of the SWT following exposure to sweeteners is an aftereffect of receptor activation while providing additional support for a role of sweetener potency. Collectively these results provide new evidence that complex inhibitory and excitatory interactions occur between lactisole and agonists of the sweet taste receptor TAS1R2-TAS1R3. Receptor mechanisms that may be responsible for these interactions are discussed in the context of the current model of the SWT and the possible contribution of allosteric modulation.
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Affiliation(s)
- Cynthia Alvarado
- The John B. Pierce Laboratory, New Haven, Connecticut, United States of America
| | - Danielle Nachtigal
- The John B. Pierce Laboratory, New Haven, Connecticut, United States of America
| | - Jay P. Slack
- Givaudan Flavors Corp, Department of Science + Technology, Cincinnati, Ohio, United States of America
| | - Barry G. Green
- The John B. Pierce Laboratory, New Haven, Connecticut, United States of America
- Department of Surgery (Otolaryngology), Yale School of Medicine, New Haven, Connecticut, United States of America
- * E-mail:
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Abstract
High-altitude environments present a range of biochemical and physiological challenges for organisms through decreases in oxygen, pressure, and temperature relative to lowland habitats. Protein-level adaptations to hypoxic high-altitude conditions have been identified in multiple terrestrial endotherms; however, comparable adaptations in aquatic ectotherms, such as fishes, have not been as extensively characterized. In enzyme proteins, cold adaptation is attained through functional trade-offs between stability and activity, often mediated by substitutions outside the active site. Little is known whether signaling proteins [e.g., G protein-coupled receptors (GPCRs)] exhibit natural variation in response to cold temperatures. Rhodopsin (RH1), the temperature-sensitive visual pigment mediating dim-light vision, offers an opportunity to enhance our understanding of thermal adaptation in a model GPCR. Here, we investigate the evolution of rhodopsin function in an Andean mountain catfish system spanning a range of elevations. Using molecular evolutionary analyses and site-directed mutagenesis experiments, we provide evidence for cold adaptation in RH1. We find that unique amino acid substitutions occur at sites under positive selection in high-altitude catfishes, located at opposite ends of the RH1 intramolecular hydrogen-bonding network. Natural high-altitude variants introduced into these sites via mutagenesis have limited effects on spectral tuning, yet decrease the stability of dark-state and light-activated rhodopsin, accelerating the decay of ligand-bound forms. As found in cold-adapted enzymes, this phenotype likely compensates for a cold-induced decrease in kinetic rates-properties of rhodopsin that mediate rod sensitivity and visual performance. Our results support a role for natural variation in enhancing the performance of GPCRs in response to cold temperatures.
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Tsukamoto H, Chen IS, Kubo Y, Furutani Y. A ciliary opsin in the brain of a marine annelid zooplankton is ultraviolet-sensitive, and the sensitivity is tuned by a single amino acid residue. J Biol Chem 2017. [PMID: 28623234 DOI: 10.1074/jbc.m117.793539] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ciliary opsins were classically thought to function only in vertebrates for vision, but they have also been identified recently in invertebrates for non-visual photoreception. Larvae of the annelid Platynereis dumerilii are used as a zooplankton model, and this zooplankton species possesses a "vertebrate-type" ciliary opsin (named c-opsin) in the brain. Platynereis c-opsin is suggested to relay light signals for melatonin production and circadian behaviors. Thus, the spectral and biochemical characteristics of this c-opsin would be directly related to non-visual photoreception in this zooplankton model. Here we demonstrate that the c-opsin can sense UV to activate intracellular signaling cascades and that it can directly bind exogenous all-trans-retinal. These results suggest that this c-opsin regulates circadian signaling in a UV-dependent manner and that it does not require a supply of 11-cis-retinal for photoreception. Avoidance of damaging UV irradiation is a major cause of large-scale daily zooplankton movement, and the observed capability of the c-opsin to transmit UV signals and bind all-trans-retinal is ideally suited for sensing UV radiation in the brain, which presumably lacks enzymes producing 11-cis-retinal. Mutagenesis analyses indicated that a unique amino acid residue (Lys-94) is responsible for c-opsin-mediated UV sensing in the Platynereis brain. We therefore propose that acquisition of the lysine residue in the c-opsin would be a critical event in the evolution of Platynereis to enable detection of ambient UV light. In summary, our findings indicate that the c-opsin possesses spectral and biochemical properties suitable for UV sensing by the zooplankton model.
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Affiliation(s)
- Hisao Tsukamoto
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, Okazaki 444-8585, Japan; Department of Structural Molecular Science, Graduate University for Advanced Studies, Hayama, Kanagawa 240-0193, Japan.
| | - I-Shan Chen
- Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan; Physiological Sciences, SOKENDAI, Graduate University for Advanced Studies, Hayama, Kanagawa 240-0193, Japan
| | - Yoshihiro Kubo
- Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan; Physiological Sciences, SOKENDAI, Graduate University for Advanced Studies, Hayama, Kanagawa 240-0193, Japan
| | - Yuji Furutani
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, Okazaki 444-8585, Japan; Department of Structural Molecular Science, Graduate University for Advanced Studies, Hayama, Kanagawa 240-0193, Japan
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Priming GPCR signaling through the synergistic effect of two G proteins. Proc Natl Acad Sci U S A 2017; 114:3756-3761. [PMID: 28325873 DOI: 10.1073/pnas.1617232114] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Although individual G-protein-coupled receptors (GPCRs) are known to activate one or more G proteins, the GPCR-G-protein interaction is viewed as a bimolecular event involving the formation of a ternary ligand-GPCR-G-protein complex. Here, we present evidence that individual GPCR-G-protein interactions can reinforce each other to enhance signaling through canonical downstream second messengers, a phenomenon we term "GPCR priming." Specifically, we find that the presence of noncognate Gq protein enhances cAMP stimulated by two Gs-coupled receptors, β2-adrenergic receptor (β2-AR) and D1 dopamine receptor (D1-R). Reciprocally, Gs enhances IP1 through vasopressin receptor (V1A-R) but not α1 adrenergic receptor (α1-AR), suggesting that GPCR priming is a receptor-specific phenomenon. The C terminus of either the Gαs or Gαq subunit is sufficient to enhance Gα subunit activation and cAMP levels. Interaction of Gαs or Gαq C termini with the GPCR increases signaling potency, suggesting an altered GPCR conformation as the underlying basis for GPCR priming. We propose three parallel mechanisms involving (i) sequential G-protein interactions at the cognate site, (ii) G-protein interactions at distinct allosteric and cognate sites on the GPCR, and (iii) asymmetric GPCR dimers. GPCR priming suggests another layer of regulation in the classic GPCR ternary-complex model, with broad implications for the multiplicity inherent in signaling networks.
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