Modulation of the Erwinia ligand-gated ion channel (ELIC) and the 5-HT3 receptor via a common vestibule site
Marijke Brams,
Cedric Govaerts,
Kumiko Kambara,
Kerry L Price,
Radovan Spurny,
Anant Gharpure,
Els Pardon,
Genevieve L Evans,
Daniel Bertrand,
Sarah CR Lummis,
Ryan E Hibbs,
Jan Steyaert,
Chris Ulens
Affiliations
Marijke Brams
Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, Faculty of Medicine, KU Leuven, Leuven, Belgium
Cedric Govaerts
Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics, Université libre de Bruxelles, Brussels, Belgium
Kumiko Kambara
HiQscreen, Geneva, Switzerland
Kerry L Price
Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
Radovan Spurny
Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, Faculty of Medicine, KU Leuven, Leuven, Belgium
Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, United States; Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
Els Pardon
Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium; VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, Faculty of Medicine, KU Leuven, Leuven, Belgium
Daniel Bertrand
HiQscreen, Geneva, Switzerland
Sarah CR Lummis
Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
Ryan E Hibbs
Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, United States; Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
Pentameric ligand-gated ion channels (pLGICs) or Cys-loop receptors are involved in fast synaptic signaling in the nervous system. Allosteric modulators bind to sites that are remote from the neurotransmitter binding site, but modify coupling of ligand binding to channel opening. In this study, we developed nanobodies (single domain antibodies), which are functionally active as allosteric modulators, and solved co-crystal structures of the prokaryote (Erwinia) channel ELIC bound either to a positive or a negative allosteric modulator. The allosteric nanobody binding sites partially overlap with those of small molecule modulators, including a vestibule binding site that is not accessible in some pLGICs. Using mutagenesis, we extrapolate the functional importance of the vestibule binding site to the human 5-HT3 receptor, suggesting a common mechanism of modulation in this protein and ELIC. Thus we identify key elements of allosteric binding sites, and extend drug design possibilities in pLGICs with an accessible vestibule site.
