Cis–trans isomerization at a proline opens the pore of a neurotransmitter-gated ion channel

Lummis, Sarah C. R.; Beene, Darren L.; Lee, Lori W.; Lester, Henry A.; Broadhurst, R. William; Dougherty, Dennis A.

doi:10.1038/nature04130

Cited by 429 publications

(421 citation statements)

References 29 publications

(1 reference statement)

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“…The binding of agonist to the orthosteric site on a Cys-loop ligand-gated ion channel induces a conformational change in the extracellular N-terminal domain, which is relayed to the TM2-TM3 loop (Lummis et al, 2005). One model of channel activation is that the movement of the TM2-TM3 loop then causes the TM2 domain to rotate leading to channel opening (Miyazawa et al, 2003).…”

Section: Discussionmentioning

confidence: 99%

The L293 residue in transmembrane domain 2 of the 5-HT3A receptor is a molecular determinant of allosteric modulation by 5-hydroxyindole

Lovinger

2008

Neuropharmacology

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Allosteric modulation of ligand-gated ion channels can play important roles in shaping synaptic transmission. The function of the 5-hydroxytryptamine (serotonin) type 3 (5-HT 3 ) receptor, a member of the Cys-loop ligand-gated ion channel superfamily, is modulated by a variety of compounds such as alcohols, anesthetics and 5-hydroxyindole (5-HI). In the present study, the molecular determinants of allosteric modulation by 5-HI were explored in N1E-115 neuroblastoma cells expressing the native 5-HT 3 receptor and HEK 293 cells transfected with the recombinant 5-HT 3A receptor using molecular biology and whole-cell patch-clamp techniques. 5-HI potentiated 5-HT-activated currents in both N1E-115 cells and HEK 293 cells, and significantly decreased current desensitization and deactivation. Substitution of Leu293 (L293, L15′) in the second transmembrane domain (TM2) with cysteine (L293C) or serine (L293S) abolished 5-HI modulation. Other mutations in the TM2 domain, such as D298A and T284F, failed to alter 5-HI modulation. The L293S mutation enhanced dopamine efficacy and converted 5-HI into a partial agonist at the mutant receptor. These data suggest that 5-HI stabilizes the 5-HT 3A receptor in the open state by decreasing both desensitization and 5-HT unbinding/channel closing; and L293 is a common site for both channel gating and allosteric modulation by 5-HI. Our observations also indicate existence of a second 5-HI recognition site on the 5-HT 3A receptor which may overlap with the 5-HT binding site and is not involved in the positive modulation by 5-HI. These findings support the idea that there are two discrete sites for 5-HI allosteric modulation and direct activation in the 5-HT 3A receptor.

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Section: Discussionmentioning

confidence: 99%

The L293 residue in transmembrane domain 2 of the 5-HT3A receptor is a molecular determinant of allosteric modulation by 5-hydroxyindole

Lovinger

2008

Neuropharmacology

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“…αP272 in M2-M3 linker is coupled not only to V46 in loop 2 but also to V135 in the cys-loop [68] . The homologous proline in M2-M3 linker of 5-HT 3 R controls channel opening and closing through its backbone cis-trans isomerization [69] . However, this proline is only conserved in nAChRs and 5-HT 3 R. In GABA A receptor, the couplings between loop2/ cys-loop to M2-M3 linker in both α and β subunits are through a charge interaction [70,71] .…”

Section: Activation Mechanismmentioning

confidence: 99%

Allosteric activation mechanism of the cys-loop receptors

et al. 2009

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Binding of a neurotransmitter to its ionotropic receptor opens a distantly located ion channel, a process termed allosteric activation. Here we review recent advances in the molecular mechanism by which the cys-loop receptors are activated with emphasis on the best studied nicotinic acetylcholine receptors (nAChRs). With a combination of affinity labeling, mutagenesis, electrophysiology, kinetic modeling, electron microscopy (EM), and crystal structure analysis, the allosteric activation mechanism is emerging. Specifically, the binding domain and gating domain are interconnected by an allosteric activation network. Agonist binding induces conformational changes, resulting in the rotation of a β sheet of aminoterminal domain and outward movement of loop 2, loop F, and cys-loop, which are coupled to the M2-M3 linker to pull the channel to open. However, there are still some controversies about the movement of the channel-lining domain M2. Nine angstrom resolution EM structure of a nAChR imaged in the open state suggests that channel opening is the result of rotation of the M2 domain. In contrast, recent crystal structures of bacterial homologues of the cys-loop receptor family in apparently open state have implied an M2 tilting model with pore dilation and quaternary twist of the whole pentameric receptor. An elegant study of the nAChR using protonation scanning of M2 domain supports a similar pore dilation activation mechanism with minimal rotation of M2. This remains to be validated with other approaches including high resolution structure determination of the mammalian cys-loop receptors in the open state.

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“…Proline cis-trans isomerization has emerged as a particularly efficient regulatory mechanism in many biological processes, including cell signaling, [62][63][64][65] neurodegeneration, 66 amyloidogenesis, 67 channel gating, 68 gene regulation, 69,70 phage and virus infection, 71,72 enzyme function, 73,74 and ligand recognition. 75 Proline isomerization is unique in that it exerts its function through multiple mechanisms involving (i) significant conformational changes caused by the 180 rotation about the prolyl bond, (ii) slow kinetics of isomerization affording a molecular timer, and (iii) the recruitment of prolyl cis-trans isomerase enzymes (PPIases).…”

Section: Protein Activity Regulation By a Proline Switchmentioning

confidence: 99%

NMR reveals novel mechanisms of protein activity regulation

Kalodimos

2011

Protein Science

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NMR spectroscopy is one of the most powerful tools for the characterization of biomolecular systems. A unique aspect of NMR is its capacity to provide an integrated insight into both the structure and intrinsic dynamics of biomolecules. In addition, NMR can provide siteresolved information about the conformation entropy of binding, as well as about energetically excited conformational states. Recent advances have enabled the application of NMR for the characterization of supramolecular systems. A summary of mechanisms underpinning protein activity regulation revealed by the application of NMR spectroscopy in a number of biological systems studied in the lab is provided.

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Cis–trans isomerization at a proline opens the pore of a neurotransmitter-gated ion channel

Cited by 429 publications

References 29 publications

The L293 residue in transmembrane domain 2 of the 5-HT3A receptor is a molecular determinant of allosteric modulation by 5-hydroxyindole

The L293 residue in transmembrane domain 2 of the 5-HT3A receptor is a molecular determinant of allosteric modulation by 5-hydroxyindole

Allosteric activation mechanism of the cys-loop receptors

NMR reveals novel mechanisms of protein activity regulation

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