Molecular basis of neurotransmission - cryo-EM structural and functional investigation of the human serotonin receptor in a lipid environment

The human serotonin transporte, hSERT terminates serotonergic signalling via reuptake of
the serotonin neurotransmitter into presynaptic neurons. hSERT is widespread in the body
being found for example in the brain, peripheral nervous systems and platelets. Abnormal
function of the transporter is linked to a variety of disorders including anxiety, depression and
obesity.
The transporter is thus a key therapeutic target with antidepressants and other drugs
inhibiting serotonin reuptake to prolong signalling. Structures of hSERT are important to
underpin understanding of function as well as recognition of diverse therapeutic drugs.
Seminal work has resulted in high-resolution structures of the transporter with bound drugs,
but these are in detergent micelles and for thermally stable mutant forms of the transporter.
As with many human membrane proteins, there is scant detailed structure and functional
analysis in a lipid bilayer. Nonetheless, the lipid membrane provides the native environment,
stabilises membrane proteins and is crucial to correct function. This PhD project aims to
advance structural understanding of hSERT in lipid nanodiscs using the current method of
choice for structural determination; cryo-EM. The student will learn a valuable range of
sought-after techniques to study human membrane proteins. These range from
overexpression in yeast, direct extraction in lipid nanodiscs and biochemical analysis to more
detailed biophysical analysis, transport and inhibitor assays. They will also assess the
influence of mutations in the transporter and drug binding in different lipid environments.
The primary supervisor, Booth is an expert in lipid nanodisc samples, hSERT purification and
functional assays, whilst the second supervisor Bisson is a cryo-EM expert. The student will
work primarily at King's in Booth's lab and the Centre for ultrastructural Imaging, as well as
at the Frances Crick Institute in Booth's satellite laboratory and using the London Consortium
for cryo-EM, LonCEM, housed at the Crick.