Rhodopsin Metarhodopsin
Rhodopsin Metarhodopsin - Related Videos
01:11
Channel Rhodopsins
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2023
Most organisms use photoreceptors to sense and respond to light. Examples of photoreceptors include bacteriorhodopsins and bacteriophytochromes in some bacteria, phytochromes in plants, and rhodopsins in the photoreceptor cells of the vertebral retina. The light-sensitive property of these receptors is because of the bound chromophores, such as bilin in the phytochromes and retinal in the rhodopsins. Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...
03:06
Investigating Prolonged Depolarizing Afterpotential (PDA) in Drosophila Photoreceptors
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2025
This video demonstrates an experimental protocol to investigate the prolonged depolarizing afterpotential (PDA) in white-eyed Drosophila. The fly's eye is exposed to intense blue light pulses to convert the photopigment rhodopsin to metarhodopsin, initiating a signaling cascade that opens positive ion channels and causes membrane depolarization. Because blue light prevents the reconversion of metarhodopsin to rhodopsin, the continuous influx of positive ions results in sustained depolarization,...
12:11
A Rhodopsin Transport Assay by High-Content Imaging Analysis
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Cited by 1 •
2019
Here, we described a high-content imaging method to quantify the transport of rhodopsin mutants associated with retinitis pigmentosa. A multiple-wavelength scoring analysis was used to quantify rhodopsin protein on the cell surface or in the whole cell.
11:13
Ex Vivo Optogenetic Dissection of Fear Circuits in Brain Slices
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Cited by 8 •
2016
Optogenetic approaches are widely used to manipulate neural activity and assess the consequences for brain function. Here, a technique is outlined that upon in vivo expression of the optical activator Channelrhodopsin, allows for ex vivo analysis of synaptic properties of specific long range and local neural connections in fear-related circuits.
06:54
Dissection of Human Retina and RPE-Choroid for Proteomic Analysis
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Cited by 7 •
2017
The human retina is composed of functionally and molecularly distinct regions, including the fovea, macula, and peripheral retina. Here, we describe a method using punch biopsies and manual removal of tissue layers from a human eye to dissect and collect these distinct retinal regions for downstream proteomic analysis.
FAQs
The absorbed photon provides the initiating event for 11-cis-retinal isomerization to all-trans-retinal. This chemical rearrangement changes the conformation of the rhodopsin molecule and produces the active metarhodopsin II state. The chromophore therefore links light absorption to protein activation, making it the molecular step that determines whether a photoreceptor begins the downstream signaling cascade.
Metarhodopsin II is the active state that couples the light-induced molecular change to intracellular signaling. It activates the G protein transducin, which then stimulates phosphodiesterase. This placement makes metarhodopsin II a functional bridge between the initial photon-driven conformational change and the biochemical reduction of cGMP that ultimately alters photoreceptor electrical activity.
After phosphodiesterase is stimulated, cGMP levels fall, causing cyclic nucleotide-gated ion channels to close. The resulting change in ion flow hyperpolarizes the photoreceptor and regulates neurotransmitter release. Thus, the pathway translates a molecular decrease in cGMP into an electrical and synaptic response, allowing light-driven signaling to influence communication from the photoreceptor to downstream neurons.
A useful analysis follows the pathway in causal order: photon absorption, 11-cis-retinal isomerization, formation of metarhodopsin II, transducin activation, phosphodiesterase stimulation, cGMP reduction, channel closure, photoreceptor hyperpolarization, and altered neurotransmitter release. Tracking this sequence helps distinguish the initiating molecular event from later electrical and synaptic outcomes in studies of retinal phototransduction.
These molecular states provide a framework for connecting light exposure with changes in photoreceptor signaling. Investigators can relate chromophore isomerization and metarhodopsin II formation to transducin, phosphodiesterase, cGMP, ion-channel behavior, membrane polarization, and neurotransmitter release. This integrated view helps explain how retinal photoreceptors convert a physical stimulus into neural information.
Disruption at any linked stage can be considered in relation to abnormal visual transduction, from the light-driven chromophore change through metarhodopsin II signaling and the cGMP-dependent channel response. Studying these transitions helps researchers connect molecular defects with altered photoreceptor physiology and neurotransmitter release, providing a mechanistic framework for investigating disorders caused by disrupted retinal signaling.