Disease relevance of Rod Outer Segments

• Phosducin (Pd), a small protein found abundantly in photoreceptors, is widely assumed to regulate light sensitivity in the rod outer segment through interaction with the heterotrimeric G protein transducin [1].
• Incubation of photolyzed bovine rod outer segment (ROS) membranes with pertussis toxin led to an inhibition of GTPase activity in an NAD-dependent reaction [2].
• Sorbitol, myo-inositol, and rod outer segment phagocytosis in cultured hRPE cells exposed to glucose. In vitro model of myo-inositol depletion hypothesis of diabetic complications [3].
• Moreover, we found that transfection of a human melanoma cell line with CD36 cDNA enabled these cells to bind and internalize isolated photoreceptor outer segments as seen by double immunofluorescent staining for surface bound and total cell-associated rod outer segments, and by measurement of cell-associated 125I-labeled rod outer segments [4].
• Lima bean agglutinin-fluorescein 5-isothiocyanate conjugate (FluNCS-lima bean lectin) interacts with specific receptor molecules on membranes both from the rod outer segment (ROS) of the frog retina and from S49 mouse lymphoma cells [5].

High impact information on Rod Outer Segments

• Rim protein (RmP) is an ABC transporter of unknown function in rod outer segment discs [6].
• Stargardt's ABCR is localized to the disc membrane of retinal rod outer segments [7].
• Photobleaching of rhodopsin in rod photoreceptors activates the visual cascade system leading to a decrease in cyclic GMP and the closure of cGMP-gated channels in the rod outer segment plasma membrane [8].
• Calcium plays an important role in the recovery of the rod outer segment to its dark state by regulating the resynthesis of cGMP by guanylate cyclase [8].
• We have perfused the inside-out preparation of a frog rod outer segment (I/O ROS, originally termed truncated ROS, and find that Ca2+ in a physiological range regulates the light-activation of PDE [9].

Chemical compound and disease context of Rod Outer Segments

• Cyclic GMP (cGMP) is the intracellular messenger mediating phototransduction in retinal rods, with its longitudinal diffusion in the rod outer segment (ROS) likely to be a factor in determining light sensitivity [10].

Biological context of Rod Outer Segments

• Role of light and rhodopsin phosphorylation in control of permeability of retinal rod outer segment disks to Ca2plus [11].
• These unique properties of RGS9 match those of the rod outer segment GAP and implicate it as a key element in the recovery phase of visual transduction [12].
• Membrane morphogenesis in retinal rod outer segments: inhibition by tunicamycin [13].
• Phagocytosis of rod outer segments by retinal pigment epithelial cells requires alpha(v)beta5 integrin for binding but not for internalization [14].
• Methylation and demethylation reactions of guanine nucleotide-binding proteins of retinal rod outer segments [15].

Anatomical context of Rod Outer Segments

• Light absorption by photoreceptor rod outer segments (ROS) leads not only to spectral and structural changes in the rhodopsin molecule but also to the activation of several enzymatic activities including GTPase [16].
• Retinol isomerase is concentrated in the pigment epithelium; this localization clarifies the role of this tissue in rhodopsin regeneration and explains the need to transfer all-trans retinol from the rod outer segments to the pigment epithelium during the visual cycle [17].
• Taking advantage of the high and reproducible yield of T gamma from the column, we analyzed the composition of T gamma subspecies in the T alpha-T beta gamma complex which did not bind with transducin-depleted rod outer segment membranes containing metarhodopsin II [18].
• Rhodopsin-to-metarhodopsin II transition triggers amplified changes in cytosol ATP and ADP in intact retinal rod outer segments [19].
• Photoexcitation of retinal rod photoreceptor cells involves the activation of cGMP enzyme cascade in which sequential activation of rhodopsin, transducin, and the cGMP phosphodiesterase in the rod outer segment constitutes the signal amplification mechanism [20].

Associations of Rod Outer Segments with chemical compounds

• Cyclic GMP can increase rod outer-segment light-sensitive current 10-fold without delay of excitation [21].
• We show here that the guanylate cyclase activity of unilluminated bovine rod outer segments increases markedly (5 to 20-fold) when the calcium level is lowered from 200 nM to 50 nM [22].
• 11-Cis vitamin A in dark-adapted rod outer segments is a probable source of prosthetic groups for rhodopsin biosynthesis [23].
• To test this idea electrophysiologically, we have injected purified GTP-binding protein that was binding a hydrolysis-resistant analogue of GTP, guanylyl imidodiphosphate (p(NH)ppG), termed Gp(NH)ppG, as well as partially purified PDE, into toad rod outer segments while recording membrane voltage [24].
• The 48K protein, a soluble protein found in rod outer segments, is purified through its specific binding to photoexcited rhodopsin and is involved in the quenching of light-induced guanosine 3',5'-monophosphate-phosphodiesterase activity [25].

Gene context of Rod Outer Segments

• Monoclonal antibodies were used with Western blot analysis to localize the wild-type mouse peripherin/rds protein to isolated mouse rod outer segments and to show that it, like bovine peripherin, exists as two subunits linked by one or more disulfide bonds [26].
• By using a GCAP2-specific antibody in enzymatic assays, we confirmed that GCAP1 but not GCAP2 is the major component that stimulates GC in bovine rod outer segment homogenates [27].
• Recoverin and rhodopsin kinase activity in detergent-resistant membrane rafts from rod outer segments [28].
• We suggest that the mechanism of phosducin action is based on the reduction of transducin affinity to the membranes of rod outer segments, achieved by keeping the transducin beta gamma subunits apart from the alpha subunit [29].
• Rod outer segments isolated from bovine retina phosphorylated the FLAG-tagged GRKs in the presence of dibutyryl-cAMP, suggesting that GRK1 and GRK7 are physiologically relevant substrates [30].

Analytical, diagnostic and therapeutic context of Rod Outer Segments

• Neutron diffraction measurements on isolated retinal rod outer segments show that most of the visual pigment protein, rhodopsin, is embedded in the hydrophobic core of the disk membrane [31].
• We have injected cyclic GMP intracellularly by iontophoresis through the recording electrode into single rod outer segments of the isolated superfused retina of the toad [32].
• We report here that the activation of guanylate cyclase by low Ca is mediated by an approximately 20-kDa protein purified from bovine rod outer segments by using DEAE-Sepharose, hydroxylapatite, and reverse-phase chromatographies [33].
• The molar ratio of retinol dehydrogenase to opsin in rod outer segments estimated by enzyme-linked immunosorbent assay was 1:140 [34].
• Rhodopsin (Rho) has been extracted in n-dodecyl beta-D-maltoside (DM) from bovine retinal rod outer segments and purified to homogeneity by affinity chromatography on concanavalin A-Sepharose [35].

References