Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transducin, a retinal G-protein, has been shown to exist as heterotrimers of alpha (39,000), beta (36,000), and gamma (approximately 7,000) subunits. Blue Sepharose CL-6B column chromatography of a transducin preparation extracted with a metal-free, low salt buffer containing GTP showed three distinct alpha and two distinct beta gamma activities in frog (Rana catesbeiana) rod outer segment. The binding of a hydrolysis-resistant GTP analog in these alpha fractions was proportional to the amount of the M(r) 39,000 protein. The first alpha was eluted in a complex with an inhibitory subunit of cGMP phosphodiesterase, but alpha subunits in the second and the third fractions were not complexed with any proteins. Two-dimensional gel electrophoresis and characterization with regard to the interaction with the inhibitory subunit of cGMP phosphodiesterase suggested that the first and the second alpha s were the same protein; however, the third alpha showed different characters as follows. We designated alpha in the first two fractions as alpha 1, and alpha in the third fraction as alpha 2. Nonlinear regression analysis for the binding of a hydrolysis-resistant GTP analog to both alpha subunits revealed a single class of GTP binding sites with an apparent stoichiometry of 1 mol of GTP/mol of alpha. Compared with alpha 1, alpha 2 required larger amounts of rhodopsin and beta gamma for the binding of a hydrolysis-resistant GTP analog. alpha 2 also showed less binding with the inhibitory subunit of cGMP phosphodiesterase. Both alpha 1 and alpha 2 complexed with beta gamma or beta delta (described below) were substrates for pertussis toxin-dependent ADP-ribosylation. The protein profiles of two beta gamma fractions revealed that the main fraction was composed of a beta gamma complex; however, the second active fraction was composed of beta complexed with delta (M(r) 12,000). Compared with beta gamma, beta delta stimulated GTP binding to alpha 1 at approximately 10-fold higher concentration. Two-dimensional gel electrophoresis revealed five beta and two gamma isoforms in beta gamma. Only one beta isoform was present in beta delta. The diversity of transducin subunits may reflect different signaling pathways in visual signal transduction.
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PMID:Heterogeneity of the retinal G-protein transducin from frog rod photoreceptors. Biochemical identification and characterization of new subunits. 132 54

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. Phosducin, a 33-kDa phosphoprotein, has been shown to form a tight complex with the T beta gamma subunit of transducin. In this study, we examined the interaction of phosducin-T beta gamma and the possible regulatory role of phosducin on the cGMP cascade. Addition of phosducin to photolyzed rod outer segment (ROS) membrane reduced the GTP hydrolysis activity of transducin as well as the subsequent activation of the cGMP phosphodiesterase. Phosducin also inhibited the pertussis toxin-catalyzed ADP-ribosylation of transducin, indicating that the interaction between the T alpha and T beta gamma subunits of transducin was interrupted upon binding of phosducin. The inhibitory effects of phosducin were reversed by the addition of exogenous T beta gamma. These results suggest that phosducin is capable of regulating the amount of T beta gamma available to interact with T alpha to form the active transducin complex and thereby functions as a negative regulator of the cGMP cascade. The phosducin-induced alteration of the subunit organization of transducin was examined by chemical cross-linking method using para-phenyl dimaleimide as cross-linker. It was found that the cross-linking among T alpha and T beta gamma was blocked in the presence of phosducin. This result implies that T beta gamma may undergo a conformational change upon phosducin binding which leads to the release of T alpha. Since phosducin is a soluble protein, the interaction with transducin only occurs when transducin is dissociated from ROS disc membrane. Indeed, phosducin failed to dissociate membrane-bound transducin and did not inhibit the initial cycle of transducin activation as measured by the presteady state GTP hydrolysis. However, phosducin interacts effectively with transducin released into solution after the initial activation and blocks the re-binding of T alpha. T beta gamma to ROS membrane by forming a tight complex with T beta gamma. This interaction may play an important role in regulating the turnover of the cGMP cascade in photoreceptor cells.
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PMID:Regulation of retinal cGMP cascade by phosducin in bovine rod photoreceptor cells. Interaction of phosducin and transducin. 133 80

Transducin, the signal coupling protein of retinal rod photoreceptor cells, is one of a family of G proteins that can be inactivated by pertussis toxin. We have investigated the nature of this inactivation in order to determine (1) whether it requires the toxin-catalyzed transfer of ADP-ribose from NAD+ to cysteine-347 of the alpha subunit and (2) whether it involves locking the alpha subunit in the inactive conformation characteristic of its GDP-bound state, or is limited to disruption of binding to photoexcited rhodopsin (R*). Our results indicate that all observed effects of pertussis toxin treatment, including a shift in the electrophoretic mobility of transducin's alpha subunit and functional inactivation, require NAD+ and that the appearance of the shift parallels incorporation of ADP-ribose. We have also found that, apart from interactions with photoexcited rhodopsin, the functional properties of ADP-ribosylated transducin are essentially the same as those of unmodified transducin. Normal spontaneous nucleotide exchange kinetics and the ability to activate cGMP phosphodiesterase are preserved following quantitative ADP-ribosylation, as are the abilities to hydrolyze GTP, to bind to a dye affinity column, and to display enhanced fluorescence upon addition of Al3+ and F-. Thus, ADP-ribosylation merely blocks catalysis of transducin nucleotide exchange by R* and does not lock transducin in an inactive state.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nucleotide exchange and cGMP phosphodiesterase activation by pertussis toxin inactivated transducin. 166 Nov 43

Radioligand binding studies disclosed one class of high affinity atrial natriuretic factor (ANF) receptors on human fibroblast membranes (Kd = 66 pM; maximum number of binding sites [Bmax] = 7,000 sites/cell). ANF increased cellular cyclic guanosine monophosphate (cGMP) content and suppressed isoproterenol- and PGE1-elevated, but not basal, cAMP content. Pertussis toxin pretreatment, which maximally ADP-ribosylated Gi, the guanine nucleotide-binding protein that couples inhibitory receptors to adenylate cyclase and blocks receptor-mediated inhibition of adenylate cyclase, did not interfere with ANF suppression of isoproterenol- or PGE1-elevated cellular cAMP content. Preliminary incubation of fibroblasts with 8-bromo cGMP or phosphodiesterase inhibitors, including 3-isobutyl-1-methylxanthine, Ro 20-1724, and cilostamide, however, prevented the ANF suppression of cAMP. MB 22948, an inhibitor that is partially selective for cGMP phosphodiesterase, did not block the effect of ANF. We conclude that in these cells, unlike other systems, ANF reduces cAMP content by activating a phosphodiesterase rather than by inhibiting adenylate cyclase.
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PMID:Atrial natriuretic factor reduces cyclic adenosine monophosphate content of human fibroblasts by enhancing phosphodiesterase activity. 245 32

The antigen receptors on B lymphocytes, membrane forms of immunoglobulins, transduce signals regulating B cell growth and differentiation by activating a phosphoinositide-specific phospholipase C. In this report, we describe our recent work aimed at understanding this process in greater detail. We have shown that a GTP-binding component is a necessary cofactor in the stimulation of phospholipase C by mIgM. This component has a number of properties in common with the G protein family of receptor-effector coupling components seen in the adenylate cyclase and other signaling systems. For example, analogues of GTP that cannot be hydrolyzed stimulated mIgM-triggered phosphoinositide breakdown, and an analogue of GDP that cannot be converted to GTP inhibited the reactions. Furthermore, aluminum fluoride, which activates known G proteins, also stimulates phosphoinositide breakdown. The G protein that appears to link mIgM to phospholipase C is not one of the well characterized G proteins involved in the regulation of adenylate cyclase or cGMP phosphodiesterase (GS, Gi, and transducin), as judged by its insensitivity to two bacterial toxins that modify these G proteins, cholera toxin and pertussis toxin. Interestingly, analysis of pertussis toxin sensitivity indicates that there are at least 2 distinct G proteins that couple receptors to phospholipase C. For example, the G protein required for chemotactic peptide receptor signaling in neutrophils is sensitive to pertussis toxin, in contrast to the phosphoinositide signaling G protein in B cells. We have also begun to explore the mechanisms by which mIgM signal transduction can be modulated. Stimulation of protein kinase C with phorbol esters or synthetic DG was found to inhibit mIgM-triggered phosphoinositide breakdown. This regulation probably represents a feedback inhibition that would occur with DG produced by phosphoinositide breakdown. Alternatively, there appear to be other signaling pathways that generate DG33, and they could possibly inhibit phosphoinositide breakdown via protein kinase C. This could be an important locus of regulation during B cell activation. For example, other signals could increase or decrease the potency of this feedback inhibition, and thereby adjust the sensitivity of the B cell to antigen. Alternatively, other agents could stimulate protein kinase C directly, or could stimulate another protein kinase which can do the same thing in this regard, and thereby make the B cell insensitive to antigen by preventing antigen receptor signaling.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Signal transduction via the B cell antigen receptor: involvement of a G protein and regulation of signaling. 255 95

Recently we have shown that atrial natriuretic peptide (ANP) inhibits renin release from isolated rat renal juxtaglomerular (JG) cells. ANP in general is thought to act on its target cells by the binding to specific membrane receptors. It is the objective of this contribution to summarize our present knowledge about the sequence of events by which the occupancy of ANP receptors could lead to an inhibition of renin release from juxtaglomerular (JG) cells. It was found that ANP did not affect the intracellular concentration of calcium. ANP led to a dose dependent increase in the intracellular concentration of cyclic GMP and to a dose dependent decrease of cAMPi. Inhibition of renin release from the JG-cells by ANP was clearly correlated to the level of cGMPi and not to the level of cAMPi. Concerning the mechanism by which ANP causes a rise in cGMPi in JG-cells it was found that the effect of ANP on cGMPi was potentiated by the cGMP phosphodiesterase specific inhibitor M & B 22,948. This finding suggests that ANP enhances cGMPi by the stimulation of a guanylate cyclase rather than by the inhibition of a cGMP phosphodiesterase. Moreover, evidence was obtained that the effect of ANP on cGMP, was markedly attenuated after pretreatment of the JG-cells with pertussis toxin. Since pertussis toxin is considered to inactivate guanine nucleotide binding proteins (G-proteins), this result could indicate that ANP receptors are coupled to a guanylate cyclase via a G-protein. Experimental evidence suggests that the G-protein in question might be the inhibitory unit (Ni) of the adenylate cyclase.
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PMID:Transmembrane signalling of atrial natriuretic peptide in rat renal juxtaglomerular cells. 287 65

Transducin, the guanyl nucleotide-binding protein of the retinal light-activated cGMP phosphodiesterase system, is structurally and functionally similar to the inhibitory and stimulatory guanyl nucleotide-binding proteins, Gi and Gs, of the adenylate cyclase complex. All are heterotrimers composed of alpha, beta, and gamma subunits. Gs and Gi can be activated by NaF with AlCl3 as well as by agonists acting through specific receptors. The effects of NaF and AlCl3 on transducin were investigated in a reconstituted system consisting of the purified subunits of transducin (T alpha, T beta, gamma) and rhodopsin. NaF noncompetitively inhibited the GTPase activity of T alpha in a concentration- and time-dependent manner. Inhibition by NaF was enhanced synergistically by AlCl3 which alone only slightly inhibited GTPase activity. None of the other anions tested reproduced the effect of fluoride. Fluoride inhibited [3H]guanosine 5'-(beta, gamma-imido)triphosphate binding to T alpha and release of bound GDP. The ADP-ribosylation of T alpha by pertussis toxin and binding of T alpha to rhodopsin, both of which are enhanced in the presence of T beta gamma, were inhibited by NaF and AlCl3. These findings are consistent with the hypothesis that fluoride enhances the dissociation of T alpha from T beta gamma, resulting in the inhibition of GTP-GDP exchange, and therefore, GTP hydrolysis.
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PMID:Mechanism of inhibition of transducin GTPase activity by fluoride and aluminum. 299 38

Sarcolemmal membranes were isolated from porcine skeletal muscle by modifications of a LiBr-extraction technique. Latency determinations of acetylcholinesterase, ouabain-sensitive p-nitrophenylphosphatase, [3H]ouabain binding, and (Na+ + K+)-ATPase activities indicated that 65-76% of the membranes were sealed inside-out vesicles. The preparations were enriched in cholesterol and phospholipid, and demonstrated adenylate cyclase activity and both cAMP and cGMP phosphodiesterase activities. An indication of the purity of this fraction was that the Ca2+-ATPase activity (0.13 mumol Pi mg-1 min-1 at 37 degrees C) was 3.8% of that of porcine skeletal muscle sarcoplasmic reticulum preparations. Pertussis toxin specifically catalyzed the ADP-ribosylation of a Mr 41,000 sarcolemmal protein, indicating the presence of the inhibitory guanine nucleotide regulatory protein of adenylate cyclase, Ni. An endogenous ADP-ribosyltransferase activity, with several membrane protein substrates, was also demonstrated. The addition of exogenous cAMP-dependent protein kinase or calmodulin promoted the phosphorylation of a number of sarcolemmal proteins. The calmodulin-dependent phosphorylation exhibited an approximate K 1/2 for Ca2+ of 0.5 microM, and an approximate K 1/2 for calmodulin of 0.1 microM. 125I-Calmodulin affinity labeling of the sarcolemma, using dithiobis(succinimidyl propionate), demonstrated the presence of Mr 160,000 and 280,000 calmodulin-binding components in these membranes. These results demonstrate that this porcine preparation will be valuable in the study of skeletal muscle sarcolemmal ion transport, protein and hormonal receptors, and protein kinase-catalyzed phosphorylation.
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PMID:Components of purified sarcolemma from porcine skeletal muscle. 299 26

Light stimulates phospholipase A2 activity in rod outer segments (ROS) of bovine retina as measured by the liberation of arachidonate from phosphatidylcholine, in in vitro assays of dark-adapted ROS. A role for GTP-binding proteins (G or N proteins) in the light activation of phospholipase A2 is suggested by the capacity for guanosine 5'-O-(thiotriphosphate) (GTP gamma S) to activate phospholipase A2 in dark-adapted ROS. In contrast, addition of GTP gamma S coincident with light exposure inhibited the light activation of phospholipase A2, suggesting that phospholipase A2 activity in the ROS is under dual regulation by G proteins. Transducin, the major G protein of the ROS, mediates the activation of cGMP phosphodiesterase by light and is a substrate for both cholera and pertussis toxin. Treatment of dark-adapted ROS with either toxin inhibits both basal and light-activated phospholipase A2, mimicking the action of the toxins on the light-induced cGMP phosphodiesterase activity of ROS. There is a loss of light-sensitive phospholipase A2 activity coincident with extraction of transducin from ROS membranes. In addition, the light-sensitive phospholipase A2 activity can be partially restored by the addition of purified transducin to the extracted ROS membranes. Light activation of phospholipase A2 in ROS membranes thus occurs by a transducin-dependent mechanism.
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PMID:Light activation of phospholipase A2 in rod outer segments of bovine retina and its modulation by GTP-binding proteins. 302 1

Adenylate cyclase activity was identified in membranes isolated from bovine lens fiber cells. Basal activity, in the presence of microM Ca2+ was stimulated by either sodium fluoride, guanosine 5'-[alpha,beta-imido]triphosphate (Gpp(NH)p), or forskolin; ethylene glycolbis(2-aminoethylether) tetraacetic acid (EGTA) markedly inhibited both the basal activity and the extent of stimulation by these agents. Exogenous calmodulin enhanced the Ca2+-dependent stimulation of adenylate cyclase activity. In the presence of optimal concentrations of Ca2+ plus calmodulin, adenylate cyclase activity was approximately 15 times greater than that in the presence of EGTA. Adenylate cyclase activity was not stimulated by a number of potential agonists that included carbachol, serotonin, prostaglandin E1 (PGE1), prostaglandin E2 (PGE2), adenosine, isoproterenol epinephrine, dopamine, and phenylephrine. The presence of the Ns and Ni guanine nucleotide regulatory complexes was indicated by two observations: Cholera toxin catalyzed the adenosine diphosphate (ADP) ribosylation of a number of lens membrane proteins, including a 46,500-dalton component (likely the alpha-subunit of Ns), and Pertussis toxin catalyzed the ADP ribosylation of a single 41,000-dalton lens membrane component (likely the alpha-subunit of Ni). However, that Gpp(NH)p did not inhibit either the forskolin-activated or the calmodulin-activated adenylate cyclase activities does not indicate a role for Ni in regulating this enzyme. Both cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) phosphodiesterase activities were identified in a supernate fraction derived from bovine lens. The cAMP phosphodiesterase activity appeared to be predominantly the low Km form of the enzyme. The cGMP phosphodiesterase activity, which was Ca2+-dependent, was partly inhibited maximally by 7 microM R24571, indicating its probable calmodulin dependence.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regulation of lens cyclic nucleotide metabolism by Ca2+ plus calmodulin. 303 38


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