Abstracts - Association for Chemoreception Sciences

Oral Abstracts
#1 GIVAUDAN LECTURE:
NON-MODEL MODELS IN OLFACTION
#2 SYMPOSIUM: THE STRUCTURAL
BASIS OF CHEMOSENSORY SIGNALING
Bill S. Hansson
Max Planck Institute for Chemical Ecology, Jena, Germany
Our knowledge regarding olfactory structure and function has
taken a quantum leap since the characterization of putative
olfactory receptors both in vertebrates and insects. Still, the
understanding of both ecological and evolutionary processes is
lagging behind. What do different odors really mean to animals,
and how has the system evolved to allow them to respond
behaviorally in a relevant manner. To understand these topics
better we use both a model insect (Drosophila melanogaster),
and a number of non-model arthropods (moths, ants, primitive
insects, land-living crustaceans).
I will spend a short introductory part on recent progress in
our work on drosophilid flies, touching on investigations of
hard-wired smell-driven behavior. The rest of my talk I will
devote to non-model arthropods.
In the desert ant, Cataglyphis fortis, we have built on the classic
investigations by the group of Rüdiger Wehner in Zürich. They
demonstrated the amazing ability of these tiny insects to find
their way home in a salt desert using vector-based orientation.
In our investigations we show how the ants use odor cues to
pinpoint their nest entrance, but how this orientation is, in a
life-saving fashion, weighed against vector orientation. We also
show how the ants use olfactory cues to find their main source
of food; dead insects, in a highly efficient way, and how this
smell-based food search is independent of the home vector.
To investigate the evolution of arthropod olfactory systems
we make use of both highly primitive, archeopteran insects
(in comparison to their neopteran relatives), and of land-living
crustaceans that have entered the terrestrial environment
during the last five million years. Using a combination of
transcriptomics, electrophysiology, morphology and bioassays
we show that the neopteran divide coincides with a drastic
development in the insect olfactory system, and that some
land-living crustaceans have developed enormous central
olfactory systems, while others seem to have abandoned
olfaction.
G protein coupling GPCRs: structural and functional
insights into reciprocal G protein and GPCR interactions
Roger K. Sunahara
University of Michigan Medical School Ann Arbor, MI, USA
Recent advances in the structural biology of G protein-coupled
receptors have helped to unravel the intricacies of ligand binding.
Similarly structural and biochemical analyses of heterotrimeric
G proteins have affirmed our understanding of the mechanism
underlying effector interactions and GTPase activity. The recent
crystal structure of a prototypic GPCR, the beta 2
-adrenergic
receptor (beta 2
AR), in a complex with the stimulatory G protein,
Gs, trapped in its nucleotide-free state, has now provided models
for activation of G proteins by GPCRs. These data have helped
to delineate how hormone binding to GPCRs leads to GDP
release on G proteins, the principle step that precedes GTP
binding and G protein activation. The crystal structure, together
with data from single particle reconstructions by electron
microscopy and deuterium exchange mass spectrometry, reveal
dramatic changes in the G protein alpha-subunit. The structural
data also suggest that G proteins may allosterically regulate the
receptor by stabilizing a closed conformation on the extracellular
face of the receptor. Radioligand binding analyses suggest
that G protein coupling slows ligand dissociation, consistent
with the observed structural changes in the extracellular face.
Such structural changes account for the slower observed ligand
dissociation rates and likely account for G protein-dependent
high affinity agonist binding. Together these data support a
plausible model for the mechanism for receptor-mediated
nucleotide exchange, G protein activation and agonist binding.
Acknowledgements: GM083118
#3 SYMPOSIUM: THE STRUCTURAL
BASIS OF CHEMOSENSORY SIGNALING
Structural Determinants of TRPV Channel Activation
and Desensitization
Rachelle Gaudet
Harvard University Cambridge, MA, USA
ORAL ABSTRACTS
My lab is broadly interested in the mechanisms of signaling
and transport across cellular membranes. Much of our research
centers on TRP channels and their role in sensory perception.
We focus on temperature-sensitive ion channels, particularly
TRPV1 and TRPA1. TRP channels are challenging structural
biology targets because they are large multidomain eukaryotic
membrane proteins and are not naturally abundant. We
take complementary approaches to obtain structural and
functional information on TRP channels. One strategy is to
divide and conquer: determine crystal structures of isolated
domains of TRP channels. The results can then combined with
Abstracts are printed as submitted by the author(s).
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