Disease relevance of Phototransduction

• The Drosophila retinal degeneration B (rdgB) gene encodes an integral membrane protein involved in phototransduction and prevention of retinal degeneration [1].
• Melanopsin, a presumptive photopigment, is an essential component in the phototransduction cascade within these intrinsically photosensitive ganglion cells and plays an important role in the retinal photoentrainment pathway [2].

Psychiatry related information on Phototransduction

• The authors conclude that extraocular phototransduction is not capable of shifting the phase of the hamster's locomotor activity rhythm or of suppressing pineal melatonin synthesis [3].
• Bilirubin, REM sleep, and phototransduction of environmental time cues. A hypothesis [4].

High impact information on Phototransduction

• We also analyzed light responses in a variety of mutant and transgenic backgrounds and demonstrate the importance of calmodulin in mediating calcium-dependent negative regulation of phototransduction [5].
• TRP: its role in phototransduction and store-operated Ca2+ entry [6].
• Three of these encode members of the rod photoreceptor visual transduction cascade: rhodopsin, the rod cGMP-gated cation channel alpha subunit, and the beta subunit of cGMP-phosphodiesterase (PDEB) [7].
• Cyclic GMP and calcium mediate phytochrome phototransduction [8].
• PDE beta is the second member of the phototransduction cascade besides rhodopsin that is absent or altered as a cause of retinitis pigmentosa, suggesting that other members of this pathway may be defective in other forms of this disease [9].

Chemical compound and disease context of Phototransduction

• Mutant photoreceptors underwent late onset retinal degeneration; however, whole-cell recordings from young flies demonstrated that phototransduction was unaffected, quantum bumps, macroscopic responses in the presence and absence of external Ca(2+), light adaptation, and Ca(2+) release from internal stores all being normal [10].
• Defects in the Drosophila norpA (no receptor potential A) gene encoding a phosphoinositide-specific phospholipase C (PLC) block invertebrate phototransduction and lead to retinal degeneration [11].

Biological context of Phototransduction

• Deactivation of visual transduction without guanosine triphosphate hydrolysis by G protein [12].
• In some cases, RGS proteins modulate the lifetime and kinetics of both slow-acting (e.g., Ca(2+) oscillations) and fast-acting (e.g., ion conductances, phototransduction) signaling responses [13].
• Phototransduction in Drosophila occurs through the ubiquitous phosphoinositide-mediated signal transduction system [14].
• In rods, 11-cis-retinal produces a transient activation of the phototransduction cascade that precedes sensitivity recovery, thus slowing dark adaptation [15].
• Thus, the rdgB is a conditional mutant that requires the operation of some stages of the phototransduction cascade to express its characteristic phenotype [16].

Anatomical context of Phototransduction

• In Drosophila photoreceptors, the InaD protein, which consists of five PDZ domains, functions as a multivalent adaptor that brings together several components of the phototransduction cascade into a macromolecular complex [17].
• The rolling blackout (rbo) gene encodes an integral plasma membrane lipase required for Drosophila phototransduction [18].
• Although rods and cones seem to contain distinct transducin subunits, it is not known whether phototransduction in a given cell type depends strictly on a single form of each subunit [19].
• cGMP is a key regulatory molecule in visual transduction, integration of neuronal response to excitatory neurotransmitters, relaxation of smooth muscle, intestinal secretion of water and salt, and reabsorption of sodium and water in the distal tubules of the nephron [20].
• The phosphoinositide cascade mediates visual transduction in invertebrate photoreceptors [21].

Associations of Phototransduction with chemical compounds

• Calcium ions appear to have a role in this phototransduction process: they provide negative feedback between the conductance, which is permeable to Ca2+ (refs 4, 5), and the concentration of cGMP, which is sensitive to Ca2+ (refs 6-8) [22].
• These results suggest the existence of a positive feedback loop at the cone output synapse: over most of the light-response range, glutamate released by depolarization of the cone will cause further depolarization, increasing the gain of phototransduction [23].
• These results suggest a model for phototransduction, with implications for bacteriorhodopsin, photoactive proteins, PAS domains, and signalling proteins [24].
• Changes in cyclic AMP following light exposure have been reported, leading to the suggestion that in cone phototransduction cAMP assumes a role analogous to that played by cGMP in rods [25].
• Heterotrimeric GTP-binding proteins, calcium-calmodulin, cyclic guanosine 5'-phosphate, and the COP-DET-FUS class of master regulators are implicated as signaling intermediates in phototransduction [26].

Gene context of Phototransduction

• Isolation of a putative phospholipase C gene of Drosophila, norpA, and its role in phototransduction [27].
• The ninaA gene required for visual transduction in Drosophila encodes a homologue of cyclosporin A-binding protein [28].
• A photo-receptor cell-specific isoform of CDS from Drosophila is a key regulator of phototransduction, a G-protein-coupled signalling cascade mediated by phospholipase C. cds mutants cannot sustain a light-activated current as a result of depletion of PtdlnsP2 [29].
• These results indicate that eye-PKC functions in the light-dependent regulation of the phototransduction cascade in Drosophila [30].
• Epistasis studies suggest that DOC1 and DET3 act downstream from DET1 on two separate branches in the phototransduction pathway [31].

Analytical, diagnostic and therapeutic context of Phototransduction

• Chromatin immunoprecipitation assay showed that in addition to the rod phototransduction genes, Nrl might modulate the promoters of many functionally diverse genes in vivo [32].
• The spatial expression pattern determined for Ggamma(e) as well as co-immunoprecipitation experiments demonstrated that Ggamma(e) dimerizes with Gbeta(e) to form the heterodimeric Gbetagamma subunit which functions in visual transduction in the Drosophila compound eye [33].
• We hypothesized that because depletion of vitamin A blocks the initiation of phototransduction, such inhibition of functional activation should lead to decrease retinal metabolism and perfusion [34].

References