alpha7 nicotinic acetylcholine receptor allosteric modulation and native structure

Project Summary/Abstract:
Nicotinic acetylcholine receptors are pentameric ligand-gated ion channels responsible for excitatory
signaling throughout the nervous system. The α7 nicotinic receptor subtype is a widely expressed subtype that
is unique among nicotinic receptors in that it forms a functional homopentamer, desensitizes rapidly, and is
exceptionally permeable to Ca2+. It plays a prominent role in human disease with dysregulation of α7 linked to
Alzheimer’s disease, schizophrenia, and inflammation. α7’s unique characteristics and involvement in disease
have made it an attractive therapeutic target leading to the development of numerous compounds aimed at
enhancing α7 activity. Among the most promising strategies are positive allosteric modulators (PAMs). PAMs
increase receptor activity while maintaining the spatial and temporal characteristics of endogenous
neurotransmission. Despite strong functional characterization, precise modulator binding sites and structural
mechanisms of potentiation remain unknown, representing a major roadblock towards rational drug design.
Moreover, while α7 can uniquely assemble as a functional homopentamer, it can also associate with other
subtypes forming a heteromer, yielding increased diversity and altered channel properties. The degree of α7
channel diversity in native tissue is unclear. Thus, the major goal of this application is to resolve key questions
related to the α7 subtype by elucidating receptor modulation mechanisms and determining the molecular
structure of native α7. Building on previous work defining major gating cycle conformations, I aim to determine
high resolution structures of α7 complexed with numerous allosteric modulators. In parallel, I will develop a
method to purify native α7 from brain tissue and determine the structure of α7-containing channels using single
particle cryo-EM. Taken together, this work will define mechanisms of receptor modulation and native α7
structure and subunit stoichiometry, enhancing our understanding of α7 biology and pharmacology. Furthermore,
this work will provide a foundation for future native receptor purification and aid drug development towards the
entire nicotinic receptor family.

Grant Number: 5F31DA059092-03
NIH Institute/Center: NIH
Principal Investigator: Sean Burke