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PubMed2000

W276 mutation in the endothelin receptor subtype B impairs Gq coupling but not Gi or Go coupling.

The mutation of W276 to cysteine within the human endothelin receptor subtype B (ET(B)R) is associated with Hirschsprung's disease, a congenital intestinal disease. The sequence surrounding W276 is highly conserved between the endothelin receptor subtypes A and B. We have introduced sets of mutations into W275 and W276 of the ET(B)R gene, and the corresponding W257 and W258 of the ET(A)R gene, and studied their coupling properties with G(i), G(o), and G(q) in reconstituted phospholipid vesicles. The prepared mutants all showed a similar affinity for endothelin-1. The W276C/ET(B)R and W276A/ET(B)R mutants had reduced activities in G(q) coupling but not in G(i)/G(o) coupling, while the W275A/ET(B)R displayed reduced activities in G(i)/G(q) coupling, with normal G(o) coupling. On the other hand, W257A/ET(A)R and W258A/ET(A)R exhibited wild-type activities in all examined G protein couplings. These results suggest that the defects in the G(q) signaling pathway by the ET(B)R are connected with Hirschsprung's disease and that the two conserved tryptophans play distinct roles in signal transduction by the two receptor subtypes. In addition, W275 and W276, which are thought to be located near the extracellular side of the transmembrane helix 5, play important roles in forming the active structure of ET(B)R.

Amino Acid Sequence↗
PubMed2000

Integrative behavioral couple therapy: an acceptance-based, promising new treatment for couple discord.

Although traditional behavioral couple therapy (TBCT) has garnered the most empirical support of any marital treatment, concerns have been raised about both its durability and clinical significance. Integrative behavioral couple therapy (IBCT) was designed to address some of these limitations by combining strategies for fostering emotional acceptance with the change-oriented strategies of TBCT. Results of a preliminary clinical trial, in which 21 couples were randomly assigned to TBCT or IBCT, indicated that therapists could keep the 2 treatments distinct, that both husbands and wives receiving IBCT evidenced greater increases in marital satisfaction than couples receiving TBCT, and that IBCT resulted in a greater percentage of couples who either improved or recovered on the basis of clinical significance data. Although preliminary, these findings suggest that IBCT is a promising new treatment for couple discord.

Adaptation, Psychological↗
PubMed2005

Couple attachment and the quality of marital relationships: method and concept in the validation of the new couple attachment interview and coding system.

This study investigates links between adult attachment and marital quality in 73 married couples, using a new Couple Attachment Interview that was modeled after the Adult Attachment Interview but focuses on the relationship between the partners. A coding system (CAICS) comparing the interview protocol to prototypes for secure, dismissing, and preoccupied attachment styles yielded continuous ratings of all three styles, and categorical classifications of secure/insecure for each partner. The study found direct links between couple attachment and both self-reported and observed marital quality, with all three continuous scores contributing uniquely to the equations. In most cases, the continuous scores explained variation in marital quality after the categorical security scores were entered into the regressions, although categorical scores also contributed uniquely to the explanation of marital quality. Pairing of partners' scores explained significant variance in both self-reported and observed evaluations of the couple relationship. Security of couple attachment served as a mediator in the link between self-reported marital satisfaction and observed marital quality. The results illustrated the interconnection of methodological choices and theoretical advances in the study of attachment and couple relationship quality.

Adult↗
PubMed1992

Phase coupling by synaptic spread in chains of coupled neuronal oscillators.

Many neural systems behave as arrays of coupled oscillators, with characteristic phase coupling. For example, the rhythmic activation patterns giving rise to swimming in fish are characterized by a rostral-to-caudal phase delay in ventral root activity that is independent of the cycle duration. This produces a traveling wave of curvature along the body of the animal with a wavelength approximately equal to the body length. Here a simple mechanism for phase coupling in chains of equally activated oscillators is postulated: the synapses between the cells making up a "unit oscillator" are simply repeated in neighboring segments, with a reduced synaptic strength. If such coupling is asymmetric in the rostral and caudal directions, traveling waves of activity are produced. The intersegmental phase lag that develops is independent of the coupling strength over at least a tenfold range. Furthermore, for the unit oscillator believed to underlie central pattern generation in the lamprey spinal cord, such coupling can result in a phase lag that is independent of frequency.

Animals↗
PubMed1997

Structure of a laccase-mediated product of coupling of 2,4-diamino-6-nitrotoluene to guaiacol, a model for coupling of 2,4,6-trinitrotoluene metabolites to a humic organic soil matrix.

This work presents laccase-mediated model reactions for coupling of reduced 2,4,6-trinitrotoluene (TNT) metabolites to an organic soil matrix. The structure of an isolated coupling product of 2,4-diamino-6-nitrotoluene (2,4-DANT) to guaiacol as humic constituent was determined. Among several structures, the compound was identified conclusively to be the trinuclear coupling product 5-(2-amino-3-methyl-4-nitroanilino)-3,3(prm1)-dimethoxy-4,4(prm1)-diphenoqu inone. The compound has a weight of 409 g mol(sup-1) and may serve as a model reaction for the biogenic formation of bound residues in soil from TNT by coupling aminotoluenes (reduced TNT metabolites) to humic constituents. A linear correlation of the substrate consumption to the enzyme activity was detected. Based on this observation, the described reaction of 2,4-DANT coupling to guaiacol may be used for determination of laccase activity since the reaction was not inhibited by other compounds of culture supernatants. We propose a two-step mechanism for the coupling reaction because 2,4-DANT was not transformed by laccases in the absence of guaiacol and guaiacol oxidation was independent of the presence of 2,4-DANT. The first reaction step is a laccase-mediated dimerization of two guaiacol monomers with subsequent oxidation to a diphenoquinone. The second step is the nucleophilic addition of 2,4-DANT to the ortho position of the carbonyl group of the diphenoquinone structure.

Journal Article↗
PubMed2003

Analysis of adiabatic coupling between photonic crystal single-line-defect and coupled-resonator optical waveguides.

A detailed analysis of adiabatic coupling between conventional photonic crystal single-line-defect and coupled-resonator optical waveguides is reported. Adiabatic coupling by progressive variation of the radii of the spacing defects between cavities is investigated. Flat transmission spectra with coupling efficiencies greater than 90% are achieved in a broad frequency range with short coupling lengths. Moreover, we find that flat transmission at low frequencies requires longer coupling lengths partly because the requirements imposed for adiabatic transmission in photonic crystals are violated.

Journal Article↗
PubMed2001

Design and analysis of coupling methods for modular endoprosthetic systems as an alternative to the conical coupling.

Modular endoprostheses are often used in bone tumor management. However, the conical coupling that connects the various modules has several shortcomings. As an alternative, four new couplings have been developed. To find out if they have sufficient strength and show no movement during loading, each coupling was analysed using the finite element method. Bolt force and friction coefficient was varied to examine their influence. From the analysis it was concluded that coupling B, a dovetail coupling, meets all requirements and is the best alternative to the conical coupling. Sensitivity to bolt force and friction coefficient is very limited.

Biomechanical Phenomena↗
PubMed2006

Predicting G-protein coupled receptors-G-protein coupling specificity based on autocross-covariance transform.

Determining G-protein coupled receptors (GPCRs) coupling specificity is very important for further understanding the functions of receptors. A successful method in this area will benefit both basic research and drug discovery practice. Previously published methods rely on the transmembrane topology prediction at training step, even at prediction step. However, the transmembrane topology predicted by even the best algorithm is not of high accuracy. In this study, we developed a new method, autocross-covariance (ACC) transform based support vector machine (SVM), to predict coupling specificity between GPCRs and G-proteins. The primary amino acid sequences are translated into vectors based on the principal physicochemical properties of the amino acids and the data are transformed into a uniform matrix by applying ACC transform. SVMs for nonpromiscuous coupled GPCRs and promiscuous coupled GPCRs were trained and validated by jackknife test and the results thus obtained are very promising. All classifiers were also evaluated by the test datasets with good performance. Besides the high prediction accuracy, the most important feature of this method is that it does not require any transmembrane topology prediction at either training or prediction step but only the primary sequences of proteins. The results indicate that this relatively simple method is applicable. Academic users can freely download the prediction program at http://www.scucic.net/group/database/Service.asp.

Algorithms↗
PubMed2000

Coupling of the muscarinic m2 receptor to G protein-activated K(+) channels via Galpha(z) and a receptor-Galpha(z) fusion protein. Fusion between the receptor and Galpha(z) eliminates catalytic (collision) coupling.

G protein-activated K(+) channel (GIRK), which is activated by the G(betagamma) subunit of heterotrimeric G proteins, and muscarinic m2 receptor (m2R) were coexpressed in Xenopus oocytes. Acetylcholine evoked a K(+) current, I(ACh), via the endogenous pertussis toxin (PTX)-sensitive G(i/o) proteins. Activation of I(ACh) was accelerated by increasing the expression of m2R, suggesting a collision coupling mechanism in which one receptor catalytically activates several G proteins. Coexpression of the alpha subunit of the PTX-insensitive G protein G(z), Galpha(z), induced a slowly activating PTX-insensitive I(ACh), whose activation kinetics were also compatible with the collision coupling mechanism. When GIRK was coexpressed with an m2R x Galpha(z) fusion protein (tandem), in which the C terminus of m2R was tethered to the N terminus of Galpha(z), part of I(ACh) was still eliminated by PTX. Thus, the m2R of the tandem activates the tethered Galpha(z) but also the nontethered G(i/o) proteins. After PTX treatment, the speed of activation of the m2R x Galpha(z)-mediated response did not depend on the expression level of m2R x Galpha(z) and was faster than when m2R and Galpha(z) were coexpressed as separate proteins. These results demonstrate that fusing the receptor and the Galpha strengthens their coupling, support the collision-coupling mechanism between m2R and the G proteins, and suggest a noncatalytic (stoichiometric) coupling between the G protein and GIRK in this model system.

Animals↗
PubMed2007

Regulators of G-protein-coupled receptor-G-protein coupling: antidepressants mechanism of action.

There is a significant gap between advances in medication for mental disorders and the present static situation of biological diagnosis and monitoring treatment. The system of neural transmission and signal transduction is a complicated, highly regulated cascade of biochemical events. Growing evidence suggests that receptor-G-protein coupling may be involved in both the pathogenesis and treatment of mood disorders. Our knowledge concerning the basic mechanisms underlying the phenomenon of desensitization, internalization, downregulation and resensitization of the G-protein-coupled receptor has been advanced during the last decade. The present review discusses the possible involvement of regulators of G-protein-coupled receptor-G-protein coupling: beta-arrestins, G-protein-coupled receptor kinases and phosducin-like proteins, as well as beta-arrestins alternative signaling events, in the pathophysiology, diagnosis and treatment monitoring of mood disorders and in the mechanism of action of antidepressant medications.

Animals↗
PubMed1994

Inhibition of thrombin receptor signaling by a G-protein coupled receptor kinase. Functional specificity among G-protein coupled receptor kinases.

The thrombin receptor, a member of the seven membrane-spanning superfamily of G-protein coupled receptors, is activated by an irreversible proteolytic mechanism, but signaling by activated thrombin receptors shuts off soon after receptor activation. This shut-off mechanism is thought to be required for concentration-dependent responses to thrombin and an important determinant of the cell's sensitivity to thrombin. We report that the thrombin receptor is rapidly phosphorylated upon activation, consistent with the action of a G-protein-coupled receptor kinase. Moreover, the G-protein coupled receptor kinase BARK2 (beta-adrenergic receptor kinase 2) blocked signaling by thrombin receptors coexpressed in Xenopus oocytes. In this system, rhodopsin kinase was inactive and BARK1 was markedly less effective than BARK2. Thrombin receptor mutants which lacked potential serine and threonine phosphorylation sites in the receptor's cytoplasmic tail were insensitive to inhibition by exogenous BARK2 but did confer concentration-dependent responses to thrombin. Our studies demonstrate that a G-protein coupled receptor kinase can shut off thrombin receptor signaling but that additional mechanism(s) for terminating signaling exist. These studies also reveal functional specificity among G-protein coupled receptor kinases in a novel in vivo reconstitution system and show that heterologous expression of these kinases can be used to manipulate cellular responsiveness.

Amino Acid Sequence↗
PubMed2005

Understanding the conformational dependence of spin-spin coupling constants: through-bond and through-space J(31P,31P) coupling in tetraphosphane-1,4-diides [M(L)x]2[P4R4].

The characteristic dependence of J(31P,31P) spin-spin coupling constants of alkali metal tetraphosphane-1,4-diides on structure and composition has been analyzed by density functional methods. The computations confirm that the structure of the contact ion pairs is conserved in solution. Calculations on model systems M2P4H4, on naked P4H4(2-) anions, and on models including point charges, show that the role of the cations is mainly structural and to a smaller extent electrostatic. Three of the four J(P,P) coupling constants depend characteristically on the conformation of the anion, which in turn is determined by the substituents R and by cation-anion interactions. Several couplings exhibit a large through-space component and are thus strongly dependent on the relative orientation of nonbonding electron pairs on the phosphorus atoms involved. This is shown by visualization of coupling pathways using the recently introduced coupling energy density (CED), in combination with the electron localization function (ELF).

Journal Article↗
PubMed1998

The new active-coupling-pattern tilting experiment for an efficient and accurate determination of homonuclear coupling constants

A new constant-time COSY experiment which allows an efficient determination of accurate homonuclear coupling constant values is presented. Characteristic features include an improved scheme for homonuclear active-coupling-pattern tilting (ACT) and an arbitrarily scaled shift and coupling information (ASSCI) design of the F1 domain. As a result, simple and easy to interpret tilted cross-peak patterns, even for two-spin systems, are obtained with good sensitivity. The relative spacing of chemical-shift differences and coupling splittings is largely under experimental control. The effectiveness of the spectral region selective variant of the new sequence is demonstrated by a determination of the 3JHN, Halpha couplings in a peptide sample. The multiplet-selective variant is shown to produce good results with a terpene. The superiority of the new ACT scheme is additionally demonstrated by an ACT-J spectrum of the peptide. Copyright 1998 Academic Press.

Journal Article↗
PubMed1989

Pharmacological differences between muscarinic receptors coupled to phosphoinositide turnover and those coupled to adenylate cyclase inhibition.

Pharmacological differences between muscarinic cholinergic receptors coupled to phosphoinositide turnover and those coupled to adenylate cyclase were studied. Stimulation of muscarinic receptors from SK-N-SH human neuroblastoma cells resulted in phosphoinositide hydrolysis, but not in inhibition of cAMP formation. As has been shown previously, stimulation of muscarinic receptors from NG108-15 neuroblastoma x glioma cells, on the other hand, resulted in inhibition of cAMP formation without any observable phosphoinositide hydrolysis. These two cell lines provide a useful model system in which to study differential coupling of muscarinic cholinergic receptors. Inhibition of [3H]N-methyl scopolamine [( 3H]NMS) binding and inhibition of carbachol-stimulated function by the antagonists pirenzepine, AF-DX 116, and 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) were studied in this system. Pirenzepine inhibited [3H]NMS binding in both cell lines with low affinity (Ki of 130 and 160 nM in NG108-15 and SK-N-SH cells respectively), indicating that both cell lines express M2 receptors. None of the three antagonists studied exhibited any clear selectivity for the receptors in one cell line over those of the other. In contrast, several agonists including acetylcholine, bethanechol and carbachol exhibited pronounced selectivity. These agonists inhibited [3H]NMS binding to membranes from SK-N-SH cells with IC50 values that were 17-, 3- and 38-fold higher, respectively, than those of NG108-15 cells. This selectivity was still observed when whole cells rather than membranes were studied. These findings indicate that pharmacological differences between receptors coupled to phosphoinositide turnover and those coupled to cAMP inhibition can be detected with certain agonists, but not with the antagonists pirenzepine, AF-DX 116 or 4-DAMP.

1-Methyl-3-isobutylxanthine↗
PubMed1990

A simple dye-coupling assay for evaluating gap junctional communication: the importance of transcription and translation on the establishment of dye-coupling.

A simple dye-coupling assay has been developed to study gap junctional communication using a uterine cell line. The new dye-coupling assay was found to be of comparable sensitivity to an autoradiographic assay for transfer of radiolabelled nucleotide. To investigate the importance of protein synthesis in the establishment of dye-coupling under the conditions of this assay, cultures were treated with actinomycin-D and cycloheximide to inhibit transcription and translation, respectively. Inhibition of transcription had no significant effect on dye-coupling. The protein synthesis inhibitor, cycloheximide, also had no significant effect on dye-coupling at concentrations up to 1 uM, even though protein synthesis was inhibited to 19% of control.

Cell Communication↗
PubMed1999

Coupling of beta-adrenergic receptors to cardiac L-type Ca2+ channels: preferential coupling of the beta1 versus beta2 receptor subtype and evidence for PKA-independent activation of the channel.

Beta1- and beta2-adrenergic receptors (beta-ARs) co-exist in mammalian heart, and it is generally accepted that both activate adenylyl cyclase (AC), resulting in increased levels of cAMP and subsequent activation of L-type Ca2+ channels (CaCh). To investigate the contribution of each beta-AR subtype in AC and CaCh coupling, we stably expressed cardiac CaCh alpha1 and beta2 subunits along with either beta1-AR or beta2-AR in CHW fibroblasts. Co-expression of either beta-AR with CaCh subunits conferred responsiveness of AC and CaCh to isoproterenol (ISO), which was not observed in non-transfected cells. ISO-promoted cAMP formation occurred at a lower EC50 through the beta2-AR than through the beta1-AR (0.13 +/- 0.01 vs. 0.6 +/- 0.14 nM). In contrast, activation of CaCh was more efficacious via the beta1-AR than the beta2-AR (EC50 for CaCh activation = 238 +/- 33 vs. 1057 +/- 113 nM). Pre-treatment with pertussis toxin (PTX) had no effect upon the responsiveness of either cAMP formation or CaCh activation through either receptor. We conclude (1) that beta1-ARs exhibit preferential coupling to CaCh activation, versus that observed for the beta2-AR; (2) that this preferential coupling cannot be explained solely by cAMP-dependent processes; and (3) that the relative attenuation of beta2-AR-promoted CaCh activation is not due to receptor coupling to PTX-sensitive G proteins. Thus, it is likely that other subtype-specific, cAMP-independent coupling of the beta-AR to CaCh is present.

Calcium Channels↗
PubMed1995

Two-couple orthodontic appliance systems utility arches: a two-couple intrusion arch.

The utility arch is a two-couple intrusion arch wire used for control of anterior deep overbite. It is similar to a one-couple intrusion arch in that it is commonly made with rectangular wire, attached to the teeth only at the molars and the incisors and is activated for incisor intrusion by a molar tip back bend. It differs from a one-couple intrusion arch by the insertion of the incisor segment into the incisor brackets. This results in a fixed point of application of the intrusion force anterior to the incisors and, therefore, incisor rotation by the moment of the force. In addition, insertion of the rectangular wire into the incisor brackets usually creates a third-order couple for incisor rotation. Depending on how it is used, the moment of this couple may be activated in either direction and the resulting associated equilibrium forces will either supplement or reduce the vertical equilibrium forces created by the activation bends at the molars.

Dental Stress Analysis↗
PubMed1994

A novel mechanism for coupling of m4 muscarinic acetylcholine receptors to calmodulin-sensitive adenylyl cyclases: crossover from G protein-coupled inhibition to stimulation.

Muscarinic m4 acetylcholine receptors are normally coupled through Gi to inhibition of adenylyl cyclases. In the olfactory bulb and some cultured cells, however, m4 receptors can couple to stimulation of adenylyl cyclase activity. In this study, m4 receptors and specific isozymes of adenylyl cyclases were coexpressed in HEK-293 cells to characterize the mechanism(s) for m4 receptor stimulation of adenylyl cyclases. The calmodulin-sensitive type I and type III adenylyl cyclases were chosen for this study because neither enzyme is stimulated by the beta/gamma complex of G coupling proteins. M4 receptors exhibited either inhibition or stimulation of type I and III adenylyl cyclases depending upon receptor density and agonist concentration. Inhibition of adenylyl cyclase was apparently due to M4 coupling through Gi. Adenylyl cyclase stimulation through m4 receptors was not due to increases in intracellular Ca2+ and stimulation of the calmodulin-sensitive enzymes since it was evident in isolated membranes in the absence of free Ca2+ and with whole cells preloaded with the Ca2+ chelator BAPTA/AM. Stimulation of adenylyl cyclase activities by m4 receptors was apparently mediated via Gs since it was GTP-dependent, was insensitive to pertussis toxin, and was not due to beta/gamma stimulation. Synthetic peptides derived from a G protein activating region of the m4 receptor mimicked the m4-mediated stimulation of adenylyl cyclase activity. These data demonstrate a novel mechanism for muscarinic regulation of adenylyl cyclases that may involve crossover from inhibitory to stimulatory G protein coupling.

Adenylyl Cyclases↗