Disease relevance of RHO

• GRK5, overexpressed in Sf9 insect cells using the baculovirus system, was able to phosphorylate rhodopsin in a light-dependent manner [1].
• Heterozygous missense mutation in the rhodopsin gene as a cause of congenital stationary night blindness [2].
• Since the initial report of linkage of autosomal dominant retinitis pigmentosa (adRP) to the long arm of chromosome 3, several mutations in the gene encoding rhodopsin, which also maps to 3q, have been reported in adRP pedigrees [3].
• Although rhodopsin mutations typically are associated with retinal degeneration, Gly90Asp-affected subjects up to age 33 did not show clinical retinal changes [4].
• We show that expression of P23H, but not wild-type rhodopsin, results in a generalized impairment of the ubiquitin proteasome system, suggesting a mechanism for photoreceptor degeneration that links RP to a broad class of neurodegenerative diseases [5].

Psychiatry related information on RHO

• At light intensities bleaching from 160 to 5.6 X 10(6) rhodopsin molecules/rod/s, decreases in the response latency for the cGMP kinetics parallel decreases in the latent period of the electrical response [6].
• Transducin interactions with rhodopsin. Evidence for positive cooperative behavior [7].
• The performance decrement in the blue cone monochromats was probably not associated with rod saturation, as the field action spectrum to cause a just-noticeable-difference (jnd) decrement in discrimination was poorly fitted by a rhodopsin action spectrum [8].

High impact information on RHO

• All of these are seven-transmembrane-domain rhodopsin-like G protein-coupled receptors [9].
• Moreover, the high expression level of rhodopsin in the retina, its specific localization in the internal disks of the photoreceptor structures [termed rod outer segments (ROS)], and the lack of other highly abundant membrane proteins allow rhodopsin to be examined in the native disk membranes by a number of methods [10].
• Future high-resolution structural studies of rhodopsin and other GPCRs will form a basis to elucidate the detailed molecular mechanism of GPCR-mediated signal transduction [11].
• The ligand-binding pocket of rhodopsin is remarkably compact, and several apparent chromophore-protein interactions were not predicted from extensive mutagenesis or spectroscopic studies [11].
• The change in free Ca(2+) is believed to have a variety of effects on the transduction mechanism, including modulation of the rate of the guanylyl cyclase and rhodopsin kinase, alteration of the gain of the transduction cascade, and regulation of the affinity of the outer segment channels for cGMP [12].

Chemical compound and disease context of RHO

• We show here that the mutation Gly 90-->Asp (G90D) in the second transmembrane segment of rhodopsin, which causes congenital night blindness, also constitutively activates opsin [13].
• In exon 1 at codon 23 of the rhodopsin gene, a mutation resulting in a proline-to-histidine substitution has previously been observed in approximately 12% of American autosomal dominant retinitis pigmentosa (ADRP) patients [14].
• In an examination of the effect of three rhodopsin night blindness mutations on the rate of association of 11-cis-retinal with opsin, one of the mutations (G90D) was found to slow the rate of reaction by more than 80-fold [15].
• When photolyzed rhodopsin and T beta gamma were present, Gpp(NH)p and GTP gamma S decreased [32P]ADP-ribosylation by pertussis toxin [16].
• Binding of T alpha to rhodopsin and the ADP-ribosylation of T alpha by pertussis toxin, both of which are enhanced in the presence of T beta gamma, were inhibited by vanadate [17].

Biological context of RHO

• We assessed GRK activity by rhodopsin phosphorylation and GRK expression by immunoblot [18].
• These data extend the family of GRKs and suggest that GRK6 may have a substrate specificity quite distinct from beta ARK and rhodopsin kinase [19].
• Our system, based on transient gene expression and in vitro phosphorylation of rhodopsin, represents a new method to screen for pharmacological agents acting on this kinase [20].
• A point mutation of the rhodopsin gene in one form of retinitis pigmentosa [21].
• As the gene coding for rhodopsin is also assigned to the long arm of chromosome 3 and is expressed in rod photoreceptors that are affected early in this blinding disease, we searched for a mutation of the rhodopsin gene in patients with autosomal dominant retinitis pigmentosa [21].

Anatomical context of RHO

• We assessed the activity of GRKs in lymphocytes of rheumatoid arthritis (RA) patients by rhodopsin phosphorylation [22].
• It was shown that truncated mutations and one single-point mutation (E7A) greatly decreased GRK1's activity to phosphorylate photoactivated rhodopsin (Rho*), whereas the abilities of these mutants to phosphorylate a synthetic peptide substrate and to translocate from cytosol to rod outer segments on light activation were unaffected [23].
• The rod photoreceptors are responsible for night vision and use rhodopsin as the photosensitive pigment [24].
• Mutant rhodopsin recruits the cytosolic arrestin to the plasma membrane, and the rhodopsin-arrestin complex is internalized into the endocytic pathway [25].
• We found one instance of a mutation in an affected patient that was absent in both unaffected parents (i.e., a new germ-line mutation), indicating that some "isolate" cases of retinitis pigmentosa carry a mutation of the rhodopsin gene [26].

Associations of RHO with chemical compounds

• The amino terminus with a conserved glutamic acid of G protein-coupled receptor kinases is indispensable for their ability to phosphorylate photoactivated rhodopsin [23].
• The GRK protein expression and activity were determined by Western blot and phosphorylation of rhodopsin using [gamma-(32)P] adenosine triphosphate, respectively [27].
• When coupled with 11-cis-retinal in vitro, Ala292Glu rhodopsin is able to activate transducin in a light-dependent manner like wild-type rhodopsin [2].
• This demonstrates the proximity of Asp 90 and Lys 296 in the three-dimensional structure of rhodopsin and suggests that the constitutively activating mutations operate by a common molecular mechanism, disrupting a salt bridge between Lys 296 and the Schiff base counterion, Glu 113 [13].
• Three mutant opsins with alterations in their cytoplasmic loops bound 11-cis-retinal to yield pigments with native rhodopsin absorption spectra, but they failed to stimulate the guanosine triphosphatase activity of Gt [28].

Physical interactions of RHO

• Last, we show that mutation of the hydrophobic residues severely diminishes phospholipid-dependent autophosphorylation of GRK5 and phosphorylation of membrane-bound rhodopsin by GRK5 [29].
• These results suggest that autophosphorylation plays an important role in regulating the binding of RK to Rho and that the binding sites of RK and arrestin overlap at least partially [30].
• Complex formation between the heterotrimer and activated rhodopsin leads to a dramatic change in R1 motion at residue 217 in the receptor-binding alpha2/beta4 loop and smaller allosteric changes at the Galphai1-Gbetagamma interface distant from the receptor binding surface [31].
• We report here the NMR structure of Ca(2+)-bound recoverin bound to a functional N-terminal fragment of rhodopsin kinase (residues 1-25, called RK25) [32].
• Purified beta-arrestin bound to rhodopsin in a phosphorylation-dependent plus light-dependent manner [33].

Enzymatic interactions of RHO

• GRK1 phosphorylates photoactivated rhodopsin, initiating steps in its deactivation [34].
• Recombinant human GRK7 catalyzes rhodopsin phosphorylation in a light dependent manner [35].
• Truncation of the C-terminal domain or deletion of the conserved region in this domain of GRK2 resulted in a complete loss of its ability to phosphorylate rhodopsin and in an obvious decrease in its sensitivity to receptor-mediated phosphorylation of a peptide substrate [36].
• Binding studies revealed no binding of cArr to rhodopsin regardless of whether it was bleached and/or phosphorylated. cArr also failed to bind to heparin-Sepharose under conditions which rod arrestin (rArr) bound to the column [37].
• In the early steps of visual signal transduction, light-activated rhodopsin (R*) catalyzes GDP/GTP exchange in the heterotrimeric G protein (Galphabetagamma) transducin [38].

Regulatory relationships of RHO

• Rhodopsin phosphorylation by transiently expressed human beta ARK1: a new method for drug development [20].
• The role of RK in rods would thus be to accelerate inactivation of activated rhodopsin molecules that in concert with regeneration leads to the normal rate of recovery of sensitivity [39].
• Rhodopsin is a seven-transmembrane helix receptor that binds and catalytically activates the heterotrimeric G protein transducin (G(t)) [40].
• The high resolution structure of rhodopsin has greatly enhanced current understanding of G protein-coupled receptor (GPCR) structure in the off-state, but the activation process remains to be clarified [41].
• The occurrence of a guanine nucleotide binding protein activated by squid rhodopsin was established by examination of GTPase activity, guanine nucleotide binding, and cholera toxin catalyzed labeling of squid photoreceptor membranes [42].

Other interactions of RHO

• Calcium-dependent inhibition of rhodopsin kinase by recoverin represents one of the mechanisms that control adaptation to light [43].
• GRK6, overexpressed in Sf9 insect cells using the baculovirus system, was able to phosphorylate both the beta 2-adrenergic receptor and rhodopsin in a stimulus-dependent fashion, although it was significantly less active then beta ARK on these substrates [19].
• The identification herein of three putative receptor kinases indicates that in addition to beta ARK and rhodopsin kinase subfamilies, there are other receptor-kinase subfamilies that regulate the broad spectrum of G-protein-coupled receptors [44].
• Gene profiling of FACS-purified photoreceptors confirmed the role of NR2E3 as a strong suppressor of cone genes but an activator of only a subset of rod genes (including rhodopsin) in vivo [45].
• An intact N terminus of the gamma subunit is required for the Gbetagamma stimulation of rhodopsin phosphorylation by human beta-adrenergic receptor kinase-1 but not for kinase binding [46].

Analytical, diagnostic and therapeutic context of RHO

• GRK activity was assayed by rhodopsin phosphorylation, and GRK protein and mRNA expressions assessed by immunoblotting and real-time quantitative RT-PCR, respectively [47].
• The assay consists of amplifying with PCR the five exons of the rhodopsin gene and then analyzing each PCR product by DGGE [48].
• Twenty-one of these mutations have been introduced into a human rhodopsin cDNA by site-directed mutagenesis, and the encoded proteins have been produced by transfection of a human embryonic kidney cell line (293S) [49].
• We have used surface plasmon resonance to investigate the influences of Ca2+, myristoylation, and adenine nucleotides on the recoverin-rhodopsin kinase interaction [50].
• Sequence analysis of the 5.34-kb 5' flanking region of the human rhodopsin-encoding gene [51].

References