The systems of photo- and pheromone signals transduction in unicellular eukaryotes.
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3',5'-Cyclic-GMP Phosphodiesterases↗
Biomedical subjects
R N Etingof
Publications and source records attributed to R N Etingof.
Active sites of the cyclic GMP phosphodiesterase gamma-subunit of retinal rod outer segments.
Monoclonal antibodies were prepared to the gamma-subunit of the cGMP phosphodiesterase. One of them gamma p-1, suppresses the activation of phosphodiesterase through the alpha-subunit of transducin. The gamma-subunit fragment 24-45 rich in Arg and Lys residues is involved in gamma p-1 binding and is essential for the gamma-subunit interaction with transducin. Carboxypeptidase Y cleaves off seven amino acid residues from the C-terminus of the gamma-subunit resulting in phosphodiesterase activation. Thus, the C-terminal fragment of gamma-subunit participates in phosphodiesterase inhibition.
3',5'-Cyclic-GMP Phosphodiesterases↗
[Different functional domains of the molecule of gamma-subunit of 3',5'-phosphodiesterase from rod outer segments: evaluation with the use of monoclonal antibodies].
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3',5'-Cyclic-GMP Phosphodiesterases↗
[The role of GTP-binding proteins in the olfactory reception of vertebrates].
The inhibitory effect of the non-hydrolyzable GTP analog Gpp (NH) p (10(-5)-10(-3) M) on the specific binding of some natural odorants (L-3H-amino acids, boar sex pheromone analog 5 alpha-3H-androstan-3-one) and sex hormones (17 beta-3H-estradiol, 3H-testosterone and 5 alpha-3H-dihydrotestosterone) to the olfactory receptors of some vertebrates (fish, frog, sow, rat) was found. Under the same experimental conditions Gpp (NH) p did not affect the high affinity binding of 5 alpha-3H-androstan-3-one to the sow respiratory tissue preparations. It was assumed that the changes in the specific binding of odorants in the presence of guanyl nucleotides can be a suitable test for the identification of true odorant receptors which conjugate with the system of olfactory transduction through G-proteins. The existence of two forms of high affinity GTPase in the olfactory tissue was demonstrated. One of them is an integral membrane component, whereas the second one is a loosely bound to the membrane and it can be solubilized in the presence of EDTA. The role of G-proteins in the system of olfactory transduction and the problem of odorant receptor identification are discussed.
Animals↗
[The peptide activator of cyclic nucleotide phosphodiesterases: its effect on muscle contractile activity].
The presence of the peptide activator of cyclic nucleotide phosphodiesterase, which has been discovered previously in rat and calf myometrium, was studied in different rat tissues. The peptide was shown to present only in muscle tissues, except for intestinal tissue. In physiological experiments the peptide stimulated the contraction of rat uterine smooth muscle and diaphragmatic muscle. Phosphodiesterase inhibitors reduced this effect of the peptide. It is suggested that the effects of peptide are related to the changes in cyclic nucleotide levels in consequence of phosphodiesterase activation. Peptide did not change the activity of uterine adenylate cyclase.
2',3'-Cyclic-Nucleotide Phosphodiesterases↗
[Detection of peptide, an activator of cyclic nucleotide phosphodiesterases, in uterine tissue].
The soluble fraction of uterine tissue was found to contain a factor which is a potent activator of various cyclic nucleotide phosphodiesterases (with the exception of the retinal photoreceptor cell enzyme). The protein origin of this factor was established, using proteolysis, precipitation with trichloroacetic acid. The activator was purified by gel filtration on Sephadex G-25 and Biogel P-4 as well as by a highly effective liquid chromatography. The activator was shown to be a peptide with Mr = 1150 Da. The peptide was thermostable and stable within a broad range of pH. Besides phosphodiesterases, the peptide activated 5'-nucleotidase and Mg2+-ATPase of photoreceptor membranes.
2',3'-Cyclic-Nucleotide Phosphodiesterases↗
[Methylation of 3',5'-cGMP phosphodiesterase in retinal photoreceptor membranes].
It was found that the level of methylation of phosphodiesterase (EC 3.1.4.17) and of proteins with Mr 61000 and 21000-26000 Da in isolated preparations of bovine retinal outer segments was sharply increased in the presence of cGMP, but not with cAMP. Preparations of the outer segment phosphodiesterase protein inhibitor, which inhibits the cyclic nucleotide hydrolysis, significantly decreased the methylation level. The degree of the enzyme methylation depended on the functional state of the outer segments: in light-induced preparations it was higher that in the dark ones.
3',5'-Cyclic-GMP Phosphodiesterases↗
[Receptors of the olfactory cells: the problem of their identification and characteristics].
Own and some last literary data on the vertebrate olfactory receptors are summarized. Special attention is devoted to the identification of these receptors. The connection of these receptors with the proteins binding the guanosine triphosphate is demonstrated. On this basis a biochemical test to elicit the olfactory receptors is proposed. Using the boar pheromon receptor the application of this test to differentiate the true olfactory receptor and a respiratory lining component that binds the pheromon with the same characteristics like the receptor is shown. The olfactory receptors may be represented no only by the integral but also by peripheric membrane proteins. The questions on the olfactory mucosa receptors and mechanism of the signal transduction in the olfactory cell have been discussed.
Animals↗
Immunochemical study of the cyclic nucleotide system of retinal photoreceptor membranes: antibodies raised to phosphodiesterase, its protein inhibitor and GTP-binding proteins.
Monospecific precipitating antibodies raised to phosphodiesterase, its protein inhibitor and GTP-binding proteins of bovine retina photoreceptor membranes were obtained. The characterization of the antibodies was carried out by immunochemical methods and according to their functional properties as determined by their effect on enzyme activities. The antibodies were used to study the distribution of immunolike proteins in different animal retinas and to purify the inhibitor protein by the method of immunoaffinity chromatography.
Animals↗
Estradiol receptor and cyclic nucleotide phosphodiesterase: functional relationship, possible role of guanine nucleotide binding proteins.
The inhibitory effect of estradiol (10(-9)M - 2 X 10(-5)M) on the cyclic nucleotide phosphodiesterase (EC 3.1.4.17) activity of cytosol from rat uterine tissue and human myometrium and endometrium was established. The hormone action was shown to disappear due to preparative separation of the receptor and the enzyme; the effect reappeared after protein mixing. In the presence of GTP, Gpp (NH)p, NaF and cholera toxin the estradiol action on the phosphodiesterase activity was significantly decreased or failed to be revealed. The antibodies raised against G-proteins of retina photoreceptor membranes abolished the hormone action on phosphodiesterase. A conclusion is drawn that in uterine tissue there exists a functional connection between estradiol receptor and phosphodiesterase. The necessary participation of G-proteins in signal transmission is postulated.
3',5'-Cyclic-AMP Phosphodiesterases↗
[Comparative immunochemical characteristics of different phosphodiesterases of cyclic nucleotides].
Precipitating monospecific antibodies against purified bovine retinal rod outer segment phosphodiesterase (EC 3.1.4.17) were obtained from rabbit blood serum. These antibodies do not form precipitating complexes with phosphodiesterase isolated from rat or ox brain tissues or from the heart, lung, liver, kidney, testes and uterus of the rat. The antibodies inhibit the activity of retinal rod outer segment phosphodiesterase or that of rat brain, liver, heart and uterus enzyme (despite the lack of precipitation) but have no effect on the phosphodiesterase activity of preparations obtained from rat lungs, kidney or testes. The same effect on the phosphodiesterase activity of all these tissues is exerted by monovalent fragments of the antibodies. Using partially purified preparations of phosphodiesterase from retinal rod outer segments and brain of the ox and from human myometrium, the mechanisms of inhibition of the enzyme catalytic activity by the antibodies was studied. In the presence of the antibodies, the Km and V values appeared to be different, depending on the preparation. It was assumed that a certain site in the phosphodiesterase molecule is characterized by great structural rigidity. Taking into account the shifts in the Km values induced by the antibodies, the differences in the localization of the antigenic determinant in relation to the enzyme active center are discussed.
Animals↗
[GTP-binding proteins of the retinal photoreceptor membranes: purification, antibodies].
A scheme of immunization of rabbits with partially purified GTP-binding proteins isolated from ox retinal photoreceptor membranes has been developed. Using double radial immunodiffusion, it was shown that rabbit antiserum interacts with the GTP-binding proteins of the retinal phosphoreceptor membranes of ox, pig and frog. The antibodies interaction with the GTP-binding proteins of ox retinal rod outer segments was followed by immunoelectrophoresis as well as by elimination of the activating effect of the non-hydrolyzable derivative of GTP, guanyl-5'-yl-imidodiphosphate on cyclic nucleotide phosphodiesterase in illuminated photoreceptor membranes and in their extracts. A similar effect was exerted by immunoglobulins from immunized animals on the enzyme activation by NaF. Purified immunoglobulins type G did not practically interact with the GTP-binding proteins of the photoreceptor membranes.
Animals↗
[The presence of calmodulin in chemosensory structures, its purification and content].
Chemosensory tissues, bovine olfactory epithelium and barbel of dwarf sheat-fish (Ictalurus nebulosus) rich in gustatory buds were shown to contain calmodulin. The fraction of thermostable proteins which activate brain phosphodiesterase of cyclic nucleotides was purified to homogeneity by stepwise ion-exchange chromatography on DEAE-cellulose and gel filtration on Sephacryl S-300. Some properties of calmodulin from chemosensory tissues (e. g., content, molecular weight, electrophoretic mobility, degree of activation of phosphodiesterase) are similar to those of brain calmodulin.
2',3'-Cyclic-Nucleotide Phosphodiesterases↗
[Calmodulin in the olfactory membrane: detection and purification].
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Animals↗
[Effect of nucleoside triphosphates on cyclic nucleotide phosphodiesterase: role of protein modulators].
The effects of nucleoside triphosphates (ATP and GTP) on phosphodiesterase (PDE) of brain and outer segments of the retina enriched or devoid of protein modulators were studied. In the case of retinal outer segment PDE the enzyme activity was considerably inhibited by both nucleosides only when the enzyme was separated from the inhibitor. In case of brain PDE, on the contrary, the effect of the nucleosides was much more pronounced in the enzyme preparation coupled with the protein activator, calmodulin. The latter when added to brain PDE devoid of the activator in the presence of ATP and GTP considerably reduced the enzyme activity. An addition of the inhibitor simultaneously with GTP to the purified PDE of outer segments increased the PDE activity. The constants for the inhibition of brain PDE coupled with calmodulin and retinal outer segment PDE separated from the inhibitor by ATP and GTP were determined.
3',5'-Cyclic-AMP Phosphodiesterases↗
[Sensitivity of retinal pigments to the melanotropic effect of ACTH in normal and mutant rats with hereditary retinal dystrophy].
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Adrenocorticotropic Hormone↗
[Role of cyclic nucleotide phosphodiesterase in the effect of estradiol on uterine tissue].
It is shown that 17 beta-estradiol (10(-7)--10(-5) M) inhibited phosphodiesterase activity of the preparations (supernatant 100000 epsilon, 1 h) obtained from uterine tissue of sexually mature rats and did not affect adenylate cyclase activity of crude membrane fraction of this tissue. The hormone did not change phosphodiesterase activity of the preparations obtained from the brain, heart and outer segments of the retinal rods. Cytosol preparations from uterine tissue were demonstrated to be able to specific hormone binding. The antiestrogen clomifen completely blocked the binding. In the presence of clomifen estradiol had no effect on phosphodiesterase activity. It is suggested that estrogen receptors are necessary for the effect of 17 beta-estradiol on phosphodiesterase to be realized in uterine tissue.
2',3'-Cyclic-Nucleotide Phosphodiesterases↗
[Early changes in retinal 5'-nucleotidase activity in hereditary retinal degeneration].
Activity of soluble cGMP phosphodiesterase (PDE) and of two membrane enzymes, 5'-nucleotidase and Na,K-ATPase, was studied in the developing retina of rats with inherited retinal degeneration. It was found that by day 10 of life, the content of 5'-nucleotidase in the afflicted rats was significantly reduced as compared with controls. This difference was unchanged throughout the subsequent animals' life. Na,K-ATPase activity in the afflicted and normal animals was the same. Within the first 45 days of life, PDE calculated with respect to the rhodopsin content was not different as regards both the afflicted and normal rats. When calculated with respect to protein, the changes in PDE corresponded with the reported data. The data obtained allowed a suggestion to be made that changes in 5'-nucleotidase in inherited retinal degeneration are disease-specific. They are accounted for by changes in the enzymes of nonphotoreceptor retinal membranes. The changes in PDE may be regarded as secondary, correlating with variation in the number of the photoreceptor membranes.
5'-Nucleotidase↗