Structural basis for the modulation of pentameric ligand-gated ion channel function by lipids

Thompson, Mackenzie J.; Baenziger, John E.

doi:10.1016/j.bbamem.2020.183304

Cited by 29 publications

(36 citation statements)

References 145 publications

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“…A lipid-sensing role for M4 is supported further by the observation that mutations along M4 influence channel function (20)(21)(22)(23)(24). In addition, lipids bind to the interface between M4 and the adjacent TMD a-helices, M1 and M3, in several pLGIC structures (1,(25)(26)(27)(28)(29).…”

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confidence: 87%

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The functional role of the αM4 transmembrane helix in the muscle nicotinic acetylcholine receptor probed through mutagenesis and coevolutionary analyses

Thompson

Domville

Baenziger

2020

Journal of Biological Chemistry

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The activity of the muscle-type Torpedo nicotinic acetylcholine receptor (nAChR) is highly sensitive to lipids, but the underlying mechanisms remain poorly understood. The nAChR transmembrane α‑helix, M4, is positioned at the perimeter of each subunit in direct contact with lipids and likely plays a central role in lipid-sensing. To gain insight into the mechanisms underlying nAChR lipid-sensing, we use homology modeling, co-evolutionary analyses, site-directed mutagenesis and electrophysiology to examine the role of the α-subunit M4 (αM4) in the function of the adult muscle nAChR. Ala substitutions of most αM4 residues, including those in clusters of polar residues at both the N and C termini, and deletion of up to 11 C-terminal residues had little impact on the agonist-induced response. Even Ala substitutions of co-evolved pairs of residues at the interface between αM4 and the adjacent helices, αM1 and αM3, had little effect, although some impaired nAChR expression. On the other hand, Ala substitutions of Thr422 and Arg429 caused relatively large losses of function, suggesting functional roles for these specific residues. Ala substitutions of aromatic residues at the αM4-αM1/αM3 interface generally led to gains of function, as previously reported for the prokaryotic homolog, the Erwinia chrysanthemi ligand-gated ion channel (ELIC). The functional effects of individual Ala substitutions in αM4 were found to be additive, although not in a completely independent manner. Our results provide insight into the structural features of αM4 that are important. They also suggest how lipid dependent changes in αM4 structure may ultimately modify nAChR function.

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confidence: 87%

“…Pentameric ligand-gated ion channels (pLGICs) are sensitive to a variety of allosteric modulators that act on the transmembrane domain (TMD), including lipids (1)(2)(3)(4)(5). In reconstituted membranes, the prototypic pLGIC, the Torpedo nicotinic acetylcholine receptor (nAChR), requires cholesterol and anionic lipids for optimal activity.…”

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confidence: 99%

The functional role of the αM4 transmembrane helix in the muscle nicotinic acetylcholine receptor probed through mutagenesis and coevolutionary analyses

Thompson

Domville

Baenziger

2020

Journal of Biological Chemistry

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“…It is increasingly recognized that membrane receptors and transport proteins are regulated by specific lipids ( 15 – 22 ). Structural studies of these effects have typically revealed lipids bound on sites where their headgroups form ionic interactions, seemingly conferring specificity, while the alkyl chains pack against hydrophobic regions of the protein surface.…”

Section: Resultsmentioning

confidence: 99%

Bivalent recognition of fatty acyl-CoA by a human integral membrane palmitoyltransferase

Lee

Stix

Rana

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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S-acylation, also known as palmitoylation, is the most abundant form of protein lipidation in humans. This reversible posttranslational modification, which targets thousands of proteins, is catalyzed by 23 members of the DHHC family of integral membrane enzymes. DHHC enzymes use fatty acyl-CoA as the ubiquitous fatty acyl donor and become autoacylated at a catalytic cysteine; this intermediate subsequently transfers the fatty acyl group to a cysteine in the target protein. Protein S-acylation intersects with almost all areas of human physiology, and several DHHC enzymes are considered as possible therapeutic targets against diseases such as cancer. These efforts would greatly benefit from a detailed understanding of the molecular basis for this crucial enzymatic reaction. Here, we combine X-ray crystallography with all-atom molecular dynamics simulations to elucidate the structure of the precatalytic complex of human DHHC20 in complex with palmitoyl CoA. The resulting structure reveals that the fatty acyl chain inserts into a hydrophobic pocket within the transmembrane spanning region of the protein, whereas the CoA headgroup is recognized by the cytosolic domain through polar and ionic interactions. Biochemical experiments corroborate the predictions from our structural model. We show, using both computational and experimental analyses, that palmitoyl CoA acts as a bivalent ligand where the interaction of the DHHC enzyme with both the fatty acyl chain and the CoA headgroup is important for catalytic chemistry to proceed. This bivalency explains how, in the presence of high concentrations of free CoA under physiological conditions, DHHC enzymes can efficiently use palmitoyl CoA as a substrate for autoacylation.

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“…Another recent example of allosteric modulation by a lipid molecule comes from a study of ELIC, a pentameric ligand-gated ion channel (pLGIC) . Functional modulation of pLGICs by lipids is well documented [ 124 , 125 ]. The structure of the anionic channel was resolved by cryo-EM in nanodiscs and reveals a phospholipid molecule located near a conserved proline kink in transmembrane helix M4.…”

Section: Lipids As Modulators Of Ligand Bindingmentioning

confidence: 99%

Assessing the Role of Lipids in the Molecular Mechanism of Membrane Proteins

Jodaitis

Oene

Martens

2021

IJMS

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Membrane proteins have evolved to work optimally within the complex environment of the biological membrane. Consequently, interactions with surrounding lipids are part of their molecular mechanism. Yet, the identification of lipid–protein interactions and the assessment of their molecular role is an experimental challenge. Recently, biophysical approaches have emerged that are compatible with the study of membrane proteins in an environment closer to the biological membrane. These novel approaches revealed specific mechanisms of regulation of membrane protein function. Lipids have been shown to play a role in oligomerization, conformational transitions or allosteric coupling. In this review, we summarize the recent biophysical approaches, or combination thereof, that allow to decipher the role of lipid–protein interactions in the mechanism of membrane proteins.

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Structural basis for the modulation of pentameric ligand-gated ion channel function by lipids

Cited by 29 publications

References 145 publications

The functional role of the αM4 transmembrane helix in the muscle nicotinic acetylcholine receptor probed through mutagenesis and coevolutionary analyses

The functional role of the αM4 transmembrane helix in the muscle nicotinic acetylcholine receptor probed through mutagenesis and coevolutionary analyses

Bivalent recognition of fatty acyl-CoA by a human integral membrane palmitoyltransferase

Assessing the Role of Lipids in the Molecular Mechanism of Membrane Proteins

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