SPEAKER
Prof Jan STEYAERT
Francqui Research Professor at the Vrije
Universiteit Brussel (VUB)
Director, VIB-VUB Center for Structural
Biology, VIB
Director, Structural Biology Brussels,
VUB, Belgium
HOST:
Department of Infection and Immunity
RESPONSIBLE LIH SCIENTIST:
Dr Andy Chevigne (andy.chevigne@lih.lu)
www.lih.lu
Supported by:
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NANOBODY-ENABLED INVESTIGATION OF GPCR
TRANSMEMBRANE SIGNALLING: FROM STRUCTURE
TO FUNCTION TO DRUGS
ABSTRACT
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Polytopic membrane proteins such as GPCRs are
dynamic proteins that exist in an ensemble of
functionally distinct conformational states.
Crystallogenesis typically traps the most stable low
energy states, making it challenging to obtain
agonist bound active-state structures of GPCRs.
Stabilization of an active conformation of a GPCR
can be achieved in different ways. The most
physiologic approach is to use a native signaling
partner such as a G protein. An alternative to using a
G protein is to identify another binding protein that
can stabilize the same conformational state.
Antibodies evolved to bind to a diverse array of
protein structures with high affinity and specificity.
Last years, we generated Nanobodies that selectively
recognize an active state of the human beta2
adrenergic receptor (β2AR). Such Nanobodies that
faithfully mimic the effects of G protein binding
were used to obtain diffraction quality crystals and
to solve the very first structure of an active
agonist-bound state of the human 2 adrenergic
receptor, the M2R muscarinic receptor or the
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μ-opioid receptor. More interesting, we also
identified nanobodies that stabilize the β2AR•Gs
complex. One of these nanobodies was used to
obtain the high-resolution crystal structure of
this complex, providing the first view of
transmembrane signalling by a GPCR. Currently
we are applying such conformational nanobodies
for better drug design.
Nanobodies are the small (15 kDa) and stable
single domain fragments harbouring the full
antigen-binding capacity of the original heavy
chain only antibodies that naturally occur in
Camelids. Because of their unique threedimensional
structure, nanobodies have access
to cavities or clefts on the surface of proteins. The
nanobody platform has the competitive
advantage to other recombinant scaffold libraries
in that large numbers (109) of fragments harbouring
the full antigen-binding capacity of genuine in
vivo matured antibodies can be screened for high
affinity binders in a couple of days, allowing one
to fully exploit the humoral response of large
mammals against native antigens.
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* Opposite Luxembourg Institute of Health, House of BioHealth, 29, rue Henri Koch L-4354 Esch/Alzette
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