ORCID Profile
0000-0001-7513-5944
Current Organisation
University of Oxford
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Publisher: Cold Spring Harbor Laboratory
Date: 15-08-2021
DOI: 10.1101/2021.08.15.456392
Abstract: ChRmine 1 , a recently-discovered bacteriorhodopsin-like cation-conducting channelrhodopsin 1, 2 , exhibits puzzling properties (unusually-large photocurrents, exceptional red-shift in action spectrum, and extreme light-sensitivity) that have opened up new opportunities in optogenetics 1, 3–5 . ChRmine and its homologs function as light-gated ion channels, but by primary sequence more closely resemble ion pump rhodopsins the molecular mechanisms for passive channel conduction in this family of proteins, as well as the unusual properties of ChRmine itself, have remained mysterious. Here we present the cryo-electron microscopy structure of ChRmine at 2.0 Å resolution. The structure reveals striking architectural features never seen before in channelrhodopsins including trimeric assembly, a short transmembrane-helix 3 unwound in the middle of the membrane, a prominently-twisting extracellular-loop 1, remarkably-large intracellular cavities and extracellular vestibule, and an unprecedented hydrophilic pore that extends through the center of the trimer, separate from the three in idual monomer pores. Electrophysiological, spectroscopic, and computational analyses provide insight into conduction and gating of light-gated channels with these distinct design features, and point the way toward structure-guided creation of novel channelrhodopsins for optogenetic applications in biology.
Publisher: Elsevier BV
Date: 04-2018
Publisher: Cold Spring Harbor Laboratory
Date: 09-07-2021
DOI: 10.1101/2021.07.08.451580
Abstract: The iconic Sonic Hedgehog (SHH) morphogen pathway is a fundamental orchestrator of embryonic development and stem cell maintenance, and is implicated in cancers in various organs. A key step in signalling is transfer of a palmitate group to the N-terminal cysteine residue of SHH, catalysed by the multi-pass transmembrane enzyme Hedgehog acyltransferase (HHAT) resident in the endoplasmic reticulum (ER). Here, we present the high-resolution cryo-EM structure of HHAT bound to substrate analogue palmityl-coenzyme A and a SHH mimetic megabody. Surprisingly, we identified a heme group bound to an HHAT cysteine residue and show that this modification is essential for HHAT structure and function. A structure of HHAT bound to potent small molecule inhibitor IMP-1575 revealed conformational changes in the active site which occlude substrate binding. Our multidisciplinary analysis provides a detailed view of the novel mechanism by which HHAT adapts the membrane environment to transfer a long chain fatty acid across the ER membrane from cytosolic acyl-CoA to a luminal protein substrate. This structure of a member of the protein-substrate membrane-bound O-acyltransferase (MBOAT) superfamily provides a blueprint for other protein substrate MBOATs, such as WNT morphogen acyltransferase Porcupine and ghrelin O -acyltransferase GOAT, and a template for future drug discovery.
Publisher: Springer Science and Business Media LLC
Date: 07-2016
DOI: 10.1038/NATURE18934
Publisher: Elsevier BV
Date: 12-2021
Publisher: Center for Open Science
Date: 20-04-2023
Abstract: Since early 2020, the Stanford University Postdoc Association, known as SURPAS, has been building a community-oriented vision for the future of postdocs at Stanford. This effort sought to answer the question: “What do postdocs think about the postdoc role?” During this process, we analyzed historical postdoc advocacy, held twelve focus group discussions, and collected details of contemporary advocacy efforts into a single document. More than 70 in iduals engaged with the Report in the drafting stage, providing hundreds of comments to reflect the vision of the whole postdoc community at Stanford. This Report details the difficulties faced by postdocs at Stanford and provides an extensive list of recommended action items for various stakeholders, including postdoc advocacy groups, university faculty, university administrators, and national funding bodies. This Report was officially endorsed by the SURPAS Council on Thursday, March 30, 2023.
Publisher: Elsevier BV
Date: 10-2018
Publisher: Cold Spring Harbor Laboratory
Date: 21-08-2016
DOI: 10.1101/070623
Abstract: Cholesterol is necessary for the function of many G-protein coupled receptors (GPCRs). We find that cholesterol is not just necessary but also sufficient to activate signaling by the Hedgehog (Hh) pathway, a prominent cell-cell communication system in development. Cholesterol influences Hh signaling by directly activating Smoothened (SMO), an orphan GPCR that transmits the Hh signal across the membrane in all animals. Unlike most GPCRs, which are regulated by cholesterol through their heptahelical transmembrane domains, SMO is activated by cholesterol through its extracellular cysteine-rich domain (CRD). Residues shown to mediate cholesterol binding to the CRD in a recent structural analysis also dictate SMO activation, both in response to cholesterol and to native Hh ligands. Our results show that cholesterol can initiate signaling from the cell surface by engaging the extracellular domain of a GPCR and suggest that SMO activity may be regulated by local changes in cholesterol abundance or accessibility.
Publisher: MyJove Corporation
Date: 06-03-2013
DOI: 10.3791/50141
Publisher: Elsevier BV
Date: 02-2019
Publisher: eLife Sciences Publications, Ltd
Date: 05-10-2016
DOI: 10.7554/ELIFE.20304
Abstract: Cholesterol is necessary for the function of many G-protein coupled receptors (GPCRs). We find that cholesterol is not just necessary but also sufficient to activate signaling by the Hedgehog (Hh) pathway, a prominent cell-cell communication system in development. Cholesterol influences Hh signaling by directly activating Smoothened (SMO), an orphan GPCR that transmits the Hh signal across the membrane in all animals. Unlike many GPCRs, which are regulated by cholesterol through their heptahelical transmembrane domains, SMO is activated by cholesterol through its extracellular cysteine-rich domain (CRD). Residues shown to mediate cholesterol binding to the CRD in a recent structural analysis also dictate SMO activation, both in response to cholesterol and to native Hh ligands. Our results show that cholesterol can initiate signaling from the cell surface by engaging the extracellular domain of a GPCR and suggest that SMO activity may be regulated by local changes in cholesterol abundance or accessibility.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 03-06-2022
Abstract: Smoothened (SMO) transduces the Hedgehog (Hh) signal across the plasma membrane in response to accessible cholesterol. Cholesterol binds SMO at two sites: one in the extracellular cysteine-rich domain (CRD) and a second in the transmembrane domain (TMD). How these two sterol-binding sites mediate SMO activation in response to the ligand Sonic Hedgehog (SHH) remains unknown. We find that mutations in the CRD (but not the TMD) reduce the fold increase in SMO activity triggered by SHH. SHH also promotes the photocrosslinking of a sterol analog to the CRD in intact cells. In contrast, sterol binding to the TMD site boosts SMO activity regardless of SHH exposure. Mutational and computational analyses show that these sites are in allosteric communication despite being 45 angstroms apart. Hence, sterols function as both SHH-regulated orthosteric ligands at the CRD and allosteric ligands at the TMD to regulate SMO activity and Hh signaling.
Publisher: Cold Spring Harbor Laboratory
Date: 31-10-2022
DOI: 10.1101/2022.10.30.514430
Abstract: The KCR channelrhodopsins are recently-discovered light-gated ion channels with high K + selectivity, a property that has attracted broad attention among biologists– due to intense interest in creating novel inhibitory tools for optogenetics leveraging this K + selectivity, and due to the mystery of how this selectivity is achieved in the first place. Indeed, the molecular and structural mechanism for K + selectivity in KCRs has remained especially puzzling since these 7-transmembrane retinal-binding proteins completely lack structural similarity with known K + channels, which generally coordinate K + in a precisely symmetric conduction pathway formed by a tight interface among multiple small monomeric channel subunits (presumably not an accessible mechanism for the large KCR rhodopsin proteins). Here we present the cryo-electron microscopy structures of two KCRs from Hyphochytrium catenoides with distinct spectral properties for light absorption and channel actuation, Hc KCR1, and Hc KCR2, at resolutions of 2.6 and 2.5 Å, respectively. Structural comparison revealed first an unusually-shaped retinal binding pocket which induces rotation of the retinal in Hc KCR2, explaining the large spectral difference between Hc KCR1 and 2. Next, our combined structural, electrophysiological, computational, and spectroscopic analyses revealed a new solution to the challenging problem of K + -selective transport. KCRs indeed do not exhibit the canonical tetrameric K + selectivity filter that specifically coordinates dehydrated K + instead, single KCR monomers form a size exclusion filter using aromatic residues at the extracellular side of the pore which inhibits passage of bulky hydrated ions. This unique feature allows KCRs to function as K + channels under relevant physiological conditions, providing not only a novel mechanism for achieving high K + permeability ratios in biological ion channels, but also a framework for designing the next generation of inhibitory optogenetic tools. The first structures of K + -selective channelrhodopsins ( Hc KCR1 and 2) are determined, revealing a K + selectivity mechanism distinctly different from canonical K + channels. The cryo-EM structures of K + -selective channelrhodopsins, Hc KCR1 and 2, in nanodisc Conditions under which naturally-occurring microbial rhodopsins have a 6-s- cis retinal Identification of key residues for high K + permeability ratios The unique K + selectivity mechanism of KCRs
Publisher: Elsevier BV
Date: 02-2022
Location: Australia
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Eamon Byrne.