Nicotinic acetylcholine receptors (AChRs) at the nerve-muscle synapse enter and recover from D(esensitized) states that remain inactive in the continuous presence of neurotransmitter. Receptor desensitization down-regulates cell responses and encodes long-term activity patterns. Our goal is to understand the AChR desensitization process at a molecular level. The essential problem of how D states are connected to C(losed) and O(pen) gating states remains unsolved. We will investigate two hypotheses: i) D, O and C are connected in a closed cycle and ii) D is not connected either to C or O but rather to a short-lived gating intermediate state. We will test the second hypothesis experimentally by using mutations and voltage to shift the point of bifurcation between gating and desensitization conformational-change pathways, towards C to produce openings upon recovery or towards O to prevent openings. Many amino acids change structure during the AChR gating and desensitization transitions, and each of these microscopic rearrangements has an associated and mostly-local free energy change. We will measure these energy changes in desensitization at two regions in the AChR transmembrane domain: i) a proline kink in M1 and ii) the hydrophobic M2 gate. Despite intensive investigation, the molecular basis of AChR desensitization has remained obscure since the process was first described 60 years ago. The experiments in this proposal will fill this substantial gap in our understanding of receptor operation.

Public Health Relevance

Synaptic receptors generate cell responses by switching between inactive and active conformations under the influence of agonists. These membrane proteins also enter and recover from refractory (Desensitized) states that fail to respond to the activating ligand. Desensitization limits cell responses by removing (temporarily) a receptor from the activatable pool. The goal of this project is to understand the molecular mechanism of desensitization in muscle nicotinic acetylcholine receptors.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM121463-02
Application #
9554973
Study Section
Biophysics of Neural Systems Study Section (BPNS)
Program Officer
Nie, Zhongzhen
Project Start
2017-09-01
Project End
2021-04-30
Budget Start
2018-05-01
Budget End
2019-04-30
Support Year
2
Fiscal Year
2018
Total Cost
Indirect Cost
Name
State University of New York at Buffalo
Department
Physiology
Type
Schools of Medicine
DUNS #
038633251
City
Amherst
State
NY
Country
United States
Zip Code
14228