Oxytocic plant cyclotides as templates for peptide G protein-coupled receptor ligand design

Koehbach, Johannes, O'Brien, Margaret, Muttenthaler, Markus, Miazzo, Marion, Akcan, Muharrem, Elliott, Alysha G., Daly, Norelle L., Harvey, Peta J., Arrowsmith, Sarah, Gunasekera, Sunithi, Smith, Terry J., Wray, Susan, Göransson, Ulf, Dawson, Philip E., Craik, David J., Freissmuth, Michael and Gruber, Christian W. (2013) Oxytocic plant cyclotides as templates for peptide G protein-coupled receptor ligand design. Proceedings of the National Academy of Sciences of the United States of America, 110 52: 21183-21188. doi:10.1073/pnas.1311183110

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Author Koehbach, Johannes
O'Brien, Margaret
Muttenthaler, Markus
Miazzo, Marion
Akcan, Muharrem
Elliott, Alysha G.
Daly, Norelle L.
Harvey, Peta J.
Arrowsmith, Sarah
Gunasekera, Sunithi
Smith, Terry J.
Wray, Susan
Göransson, Ulf
Dawson, Philip E.
Craik, David J.
Freissmuth, Michael
Gruber, Christian W.
Title Oxytocic plant cyclotides as templates for peptide G protein-coupled receptor ligand design
Journal name Proceedings of the National Academy of Sciences of the United States of America   Check publisher's open access policy
ISSN 0027-8424
1091-6490
Publication date 2013-11-18
Year available 2013
Sub-type Article (original research)
DOI 10.1073/pnas.1311183110
Open Access Status DOI
Volume 110
Issue 52
Start page 21183
End page 21188
Total pages 6
Place of publication Washington, DC, United States
Publisher National Academy of Sciences
Language eng
Abstract Cyclotides are plant peptides comprising a circular backbone and three conserved disulfide bonds that confer them with exceptional stability. They were originally discovered in Oldenlandia affinis based on their use in traditional African medicine to accelerate labor. Recently, cyclotides have been identified in numerous plant species of the coffee, violet, cucurbit, pea, potato, and grass families. Their unique structural topology, high stability, and tolerance to sequence variation make them promising templates for the development of peptide-based pharmaceuticals. However, the mechanisms underlying their biological activities remain largely unknown; specifically, a receptor for a native cyclotide has not been reported hitherto. Using bioactivity-guided fractionation of an herbal peptide extract known to indigenous healers as "kalata-kalata," the cyclotide kalata B7 was found to induce strong contractility on human uterine smooth muscle cells. Radioligand displacement and second messenger-based reporter assays confirmed the oxytocin and vasopressin V-1a receptors, members of the G protein-coupled receptor family, as molecular targets for this cyclotide. Furthermore, we show that cyclotides can serve as templates for the design of selective G protein-coupled receptor ligands by generating an oxytocin-like peptide with nanomolar affinity. This nonapeptide elicited dose-dependent contractions on human myometrium. These observations provide a proof of concept for the development of cyclotide-based peptide ligands.
Formatted abstract
Cyclotides are plant peptides comprising a circular backbone and three conserved disulfide bonds that confer them with exceptional stability. They were originally discovered in Oldenlandia affinis based on their use in traditional African medicine to accelerate labor. Recently, cyclotides have been identified in numerous plant species of the coffee, violet, cucurbit, pea, potato, and grass families. Their unique structural topology, high stability, and tolerance to sequence variation make them promising templates for the development of peptide-based pharmaceuticals. However, the mechanisms underlying their biological activities remain largely unknown; specifically, a receptor for a native cyclotide has not been reported hitherto. Using bioactivity-guided fractionation of an herbal peptide extract known to indigenous healers as “kalata-kalata,” the cyclotide kalata B7 was found to induce strong contractility on human uterine smooth muscle cells. Radioligand displacement and second messenger-based reporter assays confirmed the oxytocin and vasopressin V1a receptors, members of the G protein-coupled receptor family, as molecular targets for this cyclotide. Furthermore, we show that cyclotides can serve as templates for the design of selective G protein-coupled receptor ligands by generating an oxytocin-like peptide with nanomolar affinity. This nonapeptide elicited dose-dependent contractions on human myometrium. These observations provide a proof of concept for the development of cyclotide-based peptide ligands.

Significance G protein-coupled receptors (GPCRs) are promising drug targets: >30% of the currently marketed drugs elicit their actions by binding to these transmembrane receptors. However, only ∼10% of all GPCRs are targeted by approved drugs. Resorting to plant-derived compounds catalogued by ethnopharmacological analyses may increase this repertoire. We provide a proof of concept by analyzing the uterotonic action of an herbal remedy used in traditional African medicine. We identified cyclic peptides, investigated the molecular mechanisms underlying their uterotonic activity, and report an oxytocic plant peptide that modulates the human oxytocin/vasopressin receptors. This naturally occurring peptide served as a template for the design of an oxytocin-like nonapeptide with enhanced receptor selectivity, highlighting the potential of cyclotides for the discovery of peptide-based GPCR ligands.
Keyword Circular plant peptide
Peptide ligand design
Uterotonic
Chemical pharmacology
Peptide drugs
Q-Index Code C1
Q-Index Status Confirmed Code
Grant ID P22889-B11
254897
Institutional Status UQ
Additional Notes Published online before print: 18 November 2013.

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2014 Collection
Institute for Molecular Bioscience - Publications
 
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Created: Tue, 10 Dec 2013, 21:08:02 EST by Susan Allen on behalf of Institute for Molecular Bioscience