Structures of highly flexible intracellular domain of human \u03b17 nicotinic acetylcholine receptor

Vasyl Bondarenko,Sunil Saxena,Qiang Chen,Jonathan A Coleman,Marta M Wells,Nicole Brandon,Kevin Singewald,Joel Caporoso,Tommy S Tillman,Erik Lindahl,Matthew J Lawless,Yan Xu,Pei Tang

doi:10.1038/s41467-022-28400-x

Abstract

The intracellular domain (ICD) of Cys-loop receptors mediates diverse functions. To date, no structure of a full-length ICD is available due to challenges stemming from its dynamic nature. Here, combining nuclear magnetic resonance (NMR) and electron spin resonance experiments with Rosetta computations, we determine full-length ICD structures of the human α7 nicotinic acetylcholine receptor in a resting state. We show that ~57% of the ICD residues are in highly flexible regions, primarily in a large loop (loop L) with the most mobile segment spanning ~50 Å from the central channel axis. Loop L is anchored onto the MA helix and virtually forms two smaller loops, thereby increasing its stability. Previously known motifs for cytoplasmic binding, regulation, and signaling are found in both the helices and disordered flexible regions, supporting the essential role of the ICD conformational plasticity in orchestrating a broad range of biological processes.

Highlights

The intracellular domain (ICD) of Cys-loop receptors mediates diverse functions
Each receptor consists of an extracellular domain (ECD) containing agonist-binding sites, a transmembrane domain (TMD) enclosing a channel gate, and an intracellular domain (ICD) that refers to the regions connecting the TMD helices TM3 and TM4
The α7 nicotinic acetylcholine receptor (α7nAChR) TMD + ICD structure captures a complete picture of the ICD

Summary

Introduction

The intracellular domain (ICD) of Cys-loop receptors mediates diverse functions. The ICD mediates receptorreceptor interactions[4] and interactions with intracellular proteins that regulate diverse downstream signaling pathways[5]. It has been recognized as a potential target for drug design[6]. In the case of the ICD of Cys-loop receptors, no homolog of known structures is available, and the domain is partly unstructured rather than efficiently packed with few obvious patterns. These lead to predictions that fall in the “very low” confidence category

Methods

Findings

Conclusion