Activation of the G‐Protein‐Coupled Receptor Rhodopsin by Water

Chawla, Udeep; Perera, Suchithranga M.D.C.; Fried, Steven D.E.; Eitel, Anna R.; Mertz, Blake; Weerasinghe, Nipuna; Pitman, Michael C.; Struts, Andrey V.; Brown, Michael F.

doi:10.1002/ange.202003342

Cited by 5 publications

(7 citation statements)

References 95 publications

(144 reference statements)

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“…RLKs perceive extracellular peptide ligands. We speculate that under high VPD, the concentration of an apoplastic RLK ligand might effectively increase due to evaporation from the apoplast ( Chawla et al., 2021 ). This increase in ligand concentration could serve as the signal for initiating stomatal closure in response to high VPD, coupling a physical phenomenon (VPD) with a chemical signal.…”

Section: Discussionmentioning

confidence: 99%

Stomatal responses to VPD utilize guard cell intracellular signaling components

Zait,

Joseph,

Assmann

2024

Front. Plant Sci.

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Stomatal pores, vital for CO2 uptake and water loss regulation in plants, are formed by two specialized guard cells. Despite their importance, there is limited understanding of how guard cells sense and respond to changes in vapor pressure difference (VPD). This study leverages a selection of CO2 hyposensitive and abscisic acid (ABA) signaling mutants in Arabidopsis, including heterotrimeric G protein mutants and RLK (receptor-like kinase) mutants, along with a variety of canola cultivars to delve into the intracellular signaling mechanisms prompting stomatal closure in response to high VPD. Stomatal conductance response to step changes in VPD was measured using the LI-6800F gas exchange system. Our findings highlight that stomatal responses to VPD utilize intracellular signaling components. VPD hyposensitivity was particularly evident in mutants of the ht1 (HIGH LEAF TEMPERATURE1) gene, which encodes a protein kinase expressed mainly in guard cells, and in gpa1-3, a null mutant of the sole canonical heterotrimeric Gα subunit, previously implicated in stomatal signaling. Consequently, this research identifies a nexus in the intricate relationships between guard cell signal perception, stomatal conductance, environmental humidity, and CO2 levels.

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Section: Discussionmentioning

confidence: 99%

Stomatal responses to VPD utilize guard cell intracellular signaling components

Zait,

Joseph,

Assmann

2024

Front. Plant Sci.

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“…[70,71,86,87] Changes in the water network were observed in the transitions through different photointermediates with the greatest change occurring upon reaching the MII active state, whereby the tilting of transmembrane helices 5 and 6 opens a solvent pore on the cytosolic face of rhodopsin to allow a large influx of bulk water that ultimately hydrolyzes the Schiff base of the all-trans agonist for the release of all-trans-retinal. [63,64,[87][88][89][90][91][92] A significant amount of this bulk water is then displaced upon MII binding of transducin to elicit the phototransduction cascade. [88] The hydrolysis detailed above exhibits stereoselectivity for the all-trans configuration as demonstrated by the lack of hydrolysis of the 11-cis-locked retinal analogue that photoisomerizes to an 11,13-dicis-agonist that remains bound and thermally reverts to the mono-11-cis configuration, re-establishing ground-state rhodopsin.…”

Section: An Extensive Water Network In Rhodopsin Confers Structural I...mentioning

confidence: 99%

“…[63,64,[87][88][89][90][91][92] A significant amount of this bulk water is then displaced upon MII binding of transducin to elicit the phototransduction cascade. [88] The hydrolysis detailed above exhibits stereoselectivity for the all-trans configuration as demonstrated by the lack of hydrolysis of the 11-cis-locked retinal analogue that photoisomerizes to an 11,13-dicis-agonist that remains bound and thermally reverts to the mono-11-cis configuration, re-establishing ground-state rhodopsin. [93] The water network changes in the photoactivation of rhodopsin are highly conserved across GPCRs.…”

Section: An Extensive Water Network In Rhodopsin Confers Structural I...mentioning

confidence: 99%

A short story on how chromophore is hydrolyzed from rhodopsin for recycling

Hong

Palczewski

2023

BioEssays

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The photocycle of visual opsins is essential to maintain the light sensitivity of the retina. The early physical observations of the rhodopsin photocycle by Böll and Kühne in the 1870s inspired over a century's worth of investigations on rhodopsin biochemistry. A single photon isomerizes the Schiff‐base linked 11‐cis‐retinylidene chromophore of rhodopsin, converting it to the all‐trans agonist to elicit phototransduction through photoactivated rhodopsin (Rho*). Schiff base hydrolysis of the agonist is a key step in the photocycle, not only diminishing ongoing phototransduction but also allowing for entry and binding of fresh 11‐cis chromophore to regenerate the rhodopsin pigment and maintain light sensitivity. Many challenges have been encountered in measuring the rate of this hydrolysis, but recent advancements have facilitated studies of the hydrolysis within the native membrane environment of rhodopsin. These techniques can now be applied to study hydrolysis of agonist in other opsin proteins that mediate phototransduction or chromophore turnover. In this review, we discuss the progress that has been made in characterizing the rhodopsin photocycle and the journey to characterize the hydrolysis of its all‐trans‐retinylidene agonist.

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“…To resolve this controversy, the effect of hydration on rhodopsin activation was studied using a series of hydrophilic polymer osmolytes with different molar masses [40], Fig. 2.…”

Section: Is the Preactive MI Or Active Mii State More Hydrated?mentioning

confidence: 99%

Spectral methods for study of the G-protein-coupled receptor rhodopsin. III. Osmotic stress effects

Struts

Бармасов

Brown

2023

Optics and Spectroscopy

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We review osmotic stress studies of the G-protein-coupled receptor rhodopsin. Despite the established presence of small amounts of structural water in these receptors, the influence of bulk water on their function remains unknown. Investigations of osmotic stress effects on the GPCR archetype rhodopsin have provided unique data about the role of water in receptor activation. It was discovered that osmolytes shift the rhodopsin equilibrium after photoactivation, either to the active or inactive conformations depending on their molar mass. Experimentally at least 80 water molecules have been found to enter rhodopsin in the transition to the active state. We propose that this influx of water is a necessary condition for receptor activation. If the water movement is blocked, e.g., by large osmolytes or by dehydration, then the receptor does not undergo its functional transition. The results suggest a new model whereby rhodopsin becomes swollen and partially unfolded in the activation mechanism. Water thus acts as a powerful allosteric modulator of functioning for rhodopsin-like receptors. Keywords: G-protein-coupled receptors, membranes, optical spectroscopy, rhodopsin, signal transduction.

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Activation of the G‐Protein‐Coupled Receptor Rhodopsin by Water

Cited by 5 publications

References 95 publications

Stomatal responses to VPD utilize guard cell intracellular signaling components

Stomatal responses to VPD utilize guard cell intracellular signaling components

A short story on how chromophore is hydrolyzed from rhodopsin for recycling

Spectral methods for study of the G-protein-coupled receptor rhodopsin. III. Osmotic stress effects

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