Related Experiment Video
Updated: Aug 8, 2026
14:28
Using the Horseshoe Crab, Limulus Polyphemus, in Vision Research
Published on: July 3, 2009
Current components stimulated by different G-proteins in Limulus ventral photoreceptor
Neuroreport
|October 2, 1995
Summary
Researchers investigated G-protein involvement in Limulus ventral photoreceptor light transduction. Injecting an antibody against Gq-alpha blocked one light-activated current component, supporting the hypothesis of distinct G-protein pathways.
Area of Science:
- Neuroscience
- Cell Biology
- Phototransduction Mechanisms
Background:
- Light-activated currents in Limulus ventral photoreceptors exhibit diverse physical and pharmacological properties.
- These distinct properties suggest the involvement of multiple, separate signal transduction pathways.
- The specific G-proteins mediating these pathways remain to be fully elucidated.
Purpose of the Study:
- To determine if different G-proteins selectively activate the distinct transduction pathways in Limulus ventral photoreceptors.
- To investigate the role of Gq-alpha, a known mediator of light-dependent phospholipase C (PLC) activation, in this process.
Main Methods:
- An antiserum targeting the C-terminal sequence of Gq-alpha, conserved in squid photoreceptors, was prepared.
- This Gq-alpha specific antibody was microinjected into the ventral photoreceptor cells of Limulus.
- The effects of antibody injection on light-evoked currents and their components were analyzed.
Main Results:
- Injection of the Gq-alpha antiserum selectively blocked the second component of the light-evoked current.
- Other components of the light-activated current remained unaffected and could still be elicited.
- This demonstrates a specific role for Gq-alpha in the activation of a particular transduction pathway.
Conclusions:
- The findings support the hypothesis that distinct G-proteins selectively activate different transduction pathways in Limulus ventral photoreceptors.
- Gq-alpha is implicated in mediating a specific component of the light response, likely via PLC activation.
- This research contributes to understanding the molecular basis of phototransduction complexity in invertebrate photoreceptors.
More Related Videos
Related Concept Videos
01:11Channel Rhodopsins
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,...
Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...
01:21G-Protein Gated Ion Channels
GPCRs are primarily responsible for our sense of smell, taste, and vision. The binding of a sensory stimulus activates GPCR to stimulate effector proteins, many of which are ion channels in the sensory organs. GPCRs modulate the opening and closing of the target ion channels either directly by binding them, or by releasing second messengers that activate these channels. As ions move across the membrane, the membrane potential is altered, which induces an appropriate response.
Sensory organs,...
Sensory organs,...
01:11IP3/DAG Signaling Pathway
Membrane lipids such as phosphatidylinositol (PI) are precursors for several membrane-bound and soluble second messengers. Specific kinases phosphorylate PI and produce phosphorylated inositol phospholipids. One such inositol phospholipids are the phosphatidylinositol-4,5 bisphosphate [PI(4,5)P2], present in the inner half of the lipid bilayer. Upon ligand binding, GPCR stimulates Gq proteins to turn on phospholipase Cꞵ. Activated phospholipase Cꞵ cleaves PI(4,5)P2 and produces two-second...
01:16Calmodulin-dependent Signaling
Calmodulin (CaM) is a calcium-binding protein in eukaryotes that controls various calcium-regulated cellular processes. It has four calcium-binding sites that bind calcium to form the calcium-calmodulin ( Ca2+-CaM) complex. GPCR stimulation increases the calcium levels in the cells that bind to CaM and induces a conformational change.
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
01:30Transducer Mechanism: G Protein–Coupled Receptors
G Protein–Coupled Receptors (GPCRs) are membrane-bound receptors that transiently associate with heterotrimeric G proteins and induce an appropriate response to various stimuli. GPCRs regulate critical physiological pathways and are excellent drug targets for treating diseases such as diabetes, cancer, obesity, depression, or Alzheimer's. Nearly 35% of approved drugs implement their therapeutic effects by selectively interacting with specific GPCRs.
GPCRs are also called heptahelical, 7TM, or...
GPCRs are also called heptahelical, 7TM, or...
01:22Photoreceptors and Visual Pathways
At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...