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Biomedical subjects

Marc Thibonnier

Publications and source records attributed to Marc Thibonnier.

12 recordsLinked to original sources
PubMed2006

Arrestin binding to calmodulin: a direct interaction between two ubiquitous signaling proteins.

Arrestins serve as multi-functional regulators of G-protein coupled receptors, interacting with hundreds of different receptor subtypes and a variety of other signaling proteins. Here we identify calmodulin as a novel arrestin interaction partner using three independent methods in vitro and in cells. Arrestin preferentially binds calcium-loaded calmodulin with a Kd value of approximately 7 microM, which is within range of endogenous calmodulin concentrations. The calmodulin binding site is localized on the concave side of the C-domain and a loop in the center of the arrestin molecule, significantly overlapping with receptor and microtubule-binding sites. Using purified proteins, we found that arrestins sequester calmodulin, preventing its binding to microtubules. Nanomolar affinity of arrestins for their cognate receptors makes calmodulin an ineffective competitor for arrestin binding at relatively high receptor concentrations. The arrestin-calmodulin interaction likely regulates the localization of both proteins and their availability for other interaction partners.

Arrestins↗
PubMed2006

Soluble mimics of the cytoplasmic face of the human V1-vascular vasopressin receptor bind arrestin2 and calmodulin.

Signal transduction by G protein-coupled receptors (GPCRs) is mediated by interactions between intracellular proteins and exposed motifs on the cytoplasmic face of these receptors. Arrestins bind to GPCRs and modulate receptor function either by interfering with heterotrimeric G protein signaling or by serving as signaling adaptors themselves. Calmodulin interacts with GPCRs triggering a calcium response. We have studied the interaction of arrestin2 and calmodulin with intracellular elements of the human V1-vascular vasopressin receptor (hV1R). For this purpose, we designed, expressed, and purified soluble fusion proteins with the maltose-binding protein (MBP) from Escherichia coli that mimic the intracellular surface of the hV1R. These MBP fusion proteins bind arrestin2 and calmodulin with affinities in the micromolar range. A different series of soluble receptor analogs, named vasopressin receptor 1 elements on a soluble scaffold (V1ROSS) proteins, consist of the third intracellular loop and/or the C-terminal segment of the hV1R receptor juxtaposed on the surface of the MBP. V1ROSS proteins bind calmodulin and a truncated, phosphorylation-independent form of arrestin2 more tightly than the corresponding linear fusion proteins. Thus, embedding receptor loops within the three-dimensional structure of the MBP yields a better representation of the active conformation of these receptor loops than linear receptor peptides fused onto the C terminus of the MBP. V1ROSS proteins provide a valuable tool to study receptor interactions because they are more amenable to structural analysis than the native membrane receptor. These findings set the stage for the detailed structural analysis of these protein-protein interactions that are important for understanding the mechanism of signaling.

Amino Acid Sequence↗
PubMed2005

Mapping the binding site of six nonpeptide antagonists to the human V2-renal vasopressin receptor.

Whereas arginine vasopressin binds to its receptor subtypes V(1)R and V(2)R with equal affinity of approximately 2 nM, nonpeptide antagonists interact differently with vasopressin receptor subtypes. The V(2)R antagonist binding site was mapped by site-directed mutagenesis at six selected amino acid positions, K100D, A110W, M120V, L175Y, R202S, and F307I, predicted to be involved in antagonist binding differences between V(2) R and V(1)R. These mutations did not alter the affinity for arginine vasopressin. However, the affinity for six nonpeptide receptor antagonists SR121463B [1-[4-(N-tert-butylcarbamoyl)-2-methoxybenzenesulfonyl]-5-ethoxy-3-spiro-[4[(2 morpholinoethoxy)cy-clohexane]indoline-2-one, phosphate monohydrate cis-isomer], SR49059 [(2S)1-[(2R3S)-(5-chloro-3-(2 chlorophenyl)-1-(3,4-dimethoxybenzene-sulfonyl)-3-hydroxy-2,3-dihydro-1H-indole-2-carbonyl]-pyrrolidine-2-carboxamide], SSR149415 [(2S,4R)-1-[5-chloro-1-[(2,4-dimethoxyphenyl)sulfonyl]-3-(2-methoxyphenyl)-2-oxo-2,3-dihydro-1H-indol-3-yl]-4-hydroxy-N,N-dimethyl-2pyrrolidine carboxamide, isomer(-)], OPC21268 [1-[1-[4-(3-acetylaminopropoxy)benzoyl]-4-piperidyl]-3,4-dihydro-2(1H)-quinolinone], OPC41061 [(+/-)-4'-[(7-chloro-2,3,4,5-tetrahydro-5-hydroxy-1H-1-benzazepin-1-yl)carbonyl]-o-tolu-m-toluidide], and OPC31260, [(+/-)-5-dimethylamino-1-[4-(2-methylbenzoylamino)benzoyl]-1,2, 3,4,5-tetrahydro-1H-benzazepine monohydrochloride], was altered to varying degrees, resulting in differences up to 6000-fold. Replacement of the small alanine for the bulky tryptophan in position 110 resulted in a reduced affinity for all six antagonists. In contrast, replacement of the large methionine for the smaller valine in position 120 caused a dramatic increase in affinity, up to a K(i) of 7 fM for OPC31260. Molecular modeling revealed that the binding sites for arginine vasopressin and the nonpeptide antagonists are partially overlapping. Whereas arginine vasopressin binds on the extracellular surface of V(2) R, the nonpeptide antagonists penetrate deeper into the transmembrane region of the receptor, in particular OPC21268. The mutagenesis data point to significant differences in the shape of the V(1)R and V(2)R antagonist binding pockets. The most important factor determining the specificity of nonpeptide antagonists seems to be the shape of the binding pocket on the receptor.

Amino Acid Sequence↗
PubMed2005

A C-terminal segment of the V1R vasopressin receptor is unstructured in the crystal structure of its chimera with the maltose-binding protein.

The V1 vascular vasopressin receptor (V1R) is a G-protein-coupled receptor (GPCR) involved in the regulation of body-fluid osmolality, blood volume and blood pressure. Signal transduction is mediated by the third intracellular loop of this seven-transmembrane protein as well as by the C-terminal cytoplasmic segment. A chimera of the maltose-binding protein (MBP) and the C-terminal segment of V1R has been cloned, expressed, purified and crystallized. The crystals belong to space group P2(1), with unit-cell parameters a = 51.10, b = 66.56, c = 115.72 A, beta = 95.99 degrees. The 1.8 A crystal structure reveals the conformation of MBP and part of the linker region of this chimera, with the C-terminal segment being unstructured. This may reflect a conformational plasticity in the C-terminal segment that may be necessary for proper function of V1R.

Carrier Proteins↗
PubMed2005

Vardenafil improved patient satisfaction with erectile hardness, orgasmic function and sexual experience in men with erectile dysfunction following nerve sparing radical prostatectomy.

PURPOSE: Nerve sparing radical retropubic prostatectomy (NS-RRP) results in erectile dysfunction in a significant number of patients. Vardenafil, a potent and selective phosphodiesterase type 5 inhibitor, is generally safe. It improves International Index of Erectile Function erectile function domain scores, and penetration and erection maintenance success rates in patients who have undergone NS-RRP. We report additional parameters important to patient perceptions regarding erection quality and satisfaction with sexual experience following NS-RRP. MATERIALS AND METHODS: A total of 440 men at 58 centers throughout the United States and Canada participated in this randomized, placebo controlled, double-blind trial with 3 phases, namely baseline (4-week untreated period), treatment (12 weeks) and followup (7 days). Participants received placebo (145), 10 mg vardenafil (146) or 20 mg vardenafil (149) at home on demand but no more than once per calendar day. Efficacy and satisfaction with erection quality and sexual experience were determined during the trial. RESULTS: The 10 and 20 mg vardenafil doses were significantly superior to placebo for the International Index of Erectile Function domains for intercourse satisfaction, orgasmic function and overall satisfaction with sexual experience (vs placebo p <0.0009). Significant improvement in the satisfaction rate with erection hardness were demonstrated for each vardenafil dose compared with placebo (p <0.0001). Vardenafil was generally well tolerated. Common adverse events were headache, vasodilatation and rhinitis. CONCLUSIONS: In this difficult to treat population of men with erectile dysfunction subsequent to NS-RRP on demand treatment with vardenafil during a 3-month period significantly improved key aspects of the sexual experience important to patient quality of life.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2004

Genetics of vasopressin receptors.

Membrane receptors that couple to guanine nucleotide binding protein (GPCRs) represent one of the largest families of proteins in the genome. Because of their universal distribution and multiple actions, genetic variations of GPCRs are associated with various human diseases. For instance, the clinical phenotype of congenital nephrogenic diabetes insipidus has been linked to more than 155 loss-of-function putative mutations of the arginine vasopressin (AVP) V(2) receptor, which span each and every segment of this seven-transmembrane domain receptor. These mutant receptors, which are mostly trapped in the endoplasmic reticulum, can be rescued by membrane-permeant nonpeptidic AVP receptor antagonists. An overexpression of V(1)-vascular and V(3)-pituitary AVP receptors has been observed in some endocrine tumors. The single nucleotide polymorphism of AVP receptors in the context of complex genetic traits is currently being investigated, and preliminary findings have been reported in arterial hypertension and autism.

Animals↗
PubMed2004

Erection quality scale: initial scale development and validation.

OBJECTIVES: The Erection Quality Scale (EQS) is a new, self-report measure for assessing the quality of penile erections. It is intended to complement existing diagnostic and outcome measures (eg, International Index of Erectile Function, Sexual Encounter Profile) in both clinical practice and outcomes research in erectile dysfunction (ED). METHODS: The initial phases of development and psychometric validation of the EQS are described. Specifically, qualitative research in patients and healthy men was used to generate relevant constructs. On the basis of the findings from these phases, and recommendations from an expert panel, seven constructs were selected for inclusion. Multiple items with different formats were drafted to measure each of the key constructs. An iterative process of cognitive testing, item revision, and item reduction was used to identify the 15 most appropriate items and their optimal response scales. This version of the scale was tested in a 200-subject discriminant validity study designed to gather data for a psychometric evaluation. Participants were classified into ED-untreated, ED-treated, and healthy control groups to evaluate the discriminant validity of the measure in men with different levels of erectile function. RESULTS: The study results supported a robust single-factor structure, indicating that the EQS provides an overall index of erection quality. An intraclass correlation coefficient of 0.85 denotes adequate test-retest reliability. Furthermore, the EQS correlated well with existing measures and differentiated patients from the three ED classifications, a preliminary indication of discriminant validity. CONCLUSIONS: The findings presented provide evidence of the scale's potential utility for measuring erection quality in future studies.

Adult↗
PubMed2004

Vardenafil provides reliable efficacy over time in men with erectile dysfunction.

OBJECTIVES: To evaluate the reliability of vardenafil efficacy and tolerability within 12 weeks in a broad population of men with erectile dysfunction (ED). METHODS: In a retrospective analysis of two pivotal, Phase III, randomized, double-blind, placebo-controlled trials conducted in 107 centers, 1650 men aged 18 years or older with ED received vardenafil 5 mg, 10 mg, or 20 mg on demand for 12 to 26 weeks. Outcome measures included the first-time and subsequent overall success rate until week 12 for diary entries regarding vaginal penetration (Sexual Encounter Profile [SEP]-2), erection maintenance (SEP-3), satisfaction with erection hardness, and overall satisfaction with the sexual experience. Mean efficacy was calculated for each patient during 12 weeks and then averaged for all patients within each treatment group. RESULTS: At baseline, the intention-to-treat population had moderate ED (International Index of Erectile Function-Erectile Function domain score of 13). For SEP-2 (penetration), the first-attempt and subsequent success rate was 44% and 74% for placebo, 71% and 81% for vardenafil 5 mg, 76% and 86% for vardenafil 10 mg, and 76% and 91% for vardenafil 20 mg, respectively. For SEP-3 (maintenance), first-attempt and subsequent success rate was 25% and 56% for placebo, 51% and 76% for vardenafil 5 mg, 65% and 76% for vardenafil 10 mg, and 59% and 84% for vardenafil 20 mg, respectively. For overall satisfaction with the sexual experience, the first-attempt and subsequent success rate was 19% and 48% for placebo, 48% and 68% for vardenafil 5 mg, 57% and 72% for vardenafil 10 mg, and 56% and 79% for vardenafil 20 mg, respectively. The reliability of vardenafil was similar or slightly greater in sildenafil-naive subjects compared with prior sildenafil responders. The most common adverse events were mild-to-moderate headache, flushing, and rhinitis. CONCLUSIONS: Vardenafil provides reliable efficacy for key erectile function parameters important to patients when continuing oral treatment for ED.

Clinical Trials, Phase III as Topic↗
PubMed2004

Vardenafil improves patient satisfaction with erection hardness, orgasmic function, and overall sexual experience, while improving quality of life in men with erectile dysfunction.

PURPOSE: The North American Pivotal Trial was designed to investigate the efficacy and safety of vardenafil in males with erectile dysfunction (ED). MATERIALS AND METHODS: In this randomized, double-blind, placebo-controlled, multicenter, fixed-dose, parallel group, 6-month study, vardenafil at three doses (5 mg, 10 mg, and 20 mg) was compared to placebo with the primary efficacy variables being the International Index of Erectile Function (IIEF) Erectile Function (EF) domain score and per patient diary response success rates for penetration and maintenance of erection through completion of intercourse. Additional efficacy variables included IIEF domain scores measuring intercourse satisfaction, orgasmic function, sexual desire, and overall satisfaction. Diary entries for overall per patient satisfaction rates for hardness and sexual experience were also measured. Improvements in quality of sexual life were assessed using the Fugl-Meyer quality of life (QoL) questionnaire. RESULTS: Compared to placebo, patients taking 10 mg and 20 mg doses of vardenafil showed statistically significantly greater improvement in IIEF domain scores measuring intercourse satisfaction (10.3 and 10.3 vs. 7.7), orgasmic function (7.1 and 6.9 vs. 5.3), overall satisfaction. (7.1 and 7.1 vs. 5.2) for vardenafil 10 mg and 20 mg vs. placebo, respectively, at last observation carried forward (LOCF). Vardenafil 5 mg was statistically significantly better than placebo for the secondary IIEF domain variables of intercourse satisfaction (8.9 vs. 7.7) and overall satisfaction (6.3 vs. 5.2) for vardenafil vs. placebo, respectively, at LOCF. Per patient satisfaction rates for the secondary diary variables measuring erection hardness (38%, 52%, 58% and 18%) and overall satisfaction (45%, 58%, 62% and 23%) were dose dependent and statistically significantly superior for vardenafil at 5 mg, 10 mg and 20 mg compared with placebo, respectively. Patients' answers to the Fugl-Meyer QoL questionnaire assessing improvement in sexual life also indicated statistically significant superiority for all doses of vardenafil vs. placebo treatment. The most frequent adverse events (AE) in the 5 mg, 10 mg, and 20 mg of vardenafil and placebo groups, respectively, were: headache (10%, 22%, 21% and 4%), flushing (5%, 10%, 13% and 0%), dyspepsia (1%, 4%, 6% and < 1%), and rhinitis (9%, 14%, 17% and 5%). Most AEs were mild or moderate in severity and transient in nature. CONCLUSION: Vardenafil was superior to placebo for IIEF domain scores, per patient success rates for diary questions, and assessment of quality of sexual life, in a broad range of patients with ED irrespective of etiology or severity. Vardenafil was generally well tolerated, with most AEs being mild or moderate in severity and transient in nature.

Adult↗
PubMed2003

Vasopressin receptor antagonists in heart failure.

There is ample evidence that arginine vasopressin (AVP) is a component of the neurohormonal response to congestive heart failure (CHF). Furthermore, AVP might play a role in the development, progression and worsening of CHF. Because of the need for further improvement in the treatment of CHF, randomized clinical trials were conducted to assess the efficacy and safety of non-peptide AVP receptor antagonists in patients with CHF. In pivotal trials of three non-peptide AVP receptor antagonists, these compounds improved the fluid status, osmotic balance and hemodynamics of patients with CHF. These studies support the approval of this class of agents for the symptomatic treatment of CHF, but long-term studies are required to demonstrate their role in the outcome and quality of life of these patients.

Animals↗
PubMed2003

Sustained efficacy and tolerability of vardenafil, a highly potent selective phosphodiesterase type 5 inhibitor, in men with erectile dysfunction: results of a randomized, double-blind, 26-week placebo-controlled pivotal trial.

The durability of key efficacy response parameters and safety of vardenafil was evaluated in a pivotal trial conducted in a broad population of men with erectile dysfunction (ED) in North America. In this randomized, double-blind, placebo-controlled, multicenter, fixed-dose, parallel-group, 6-month comparison study, men >18 years of age with ED for >6 months received 5-mg, 10-mg, and 20-mg doses of vardenafil as needed for up to 26 weeks. The primary efficacy variables were the International Index of Erectile Function (IIEF)-Erectile Function (EF) domain scores, and the Sexual Encounter Profile (SEP) mean per-patient success rates for penetration (SEP question 2) and maintenance of erections (SEP question 3). Safety data were also collected over time. Improvement in all primary efficacy variables was observed in all vardenafil groups versus placebo. These improvements occurred early and were either sustained or increased through week 26. Vardenafil in 10-mg and 20-mg doses was significantly superior to placebo at all time points for all efficacy variables (P <0.01), and all doses were superior to placebo at endpoint (P <0.001). Most treatment-emergent adverse events (headache, flushing, dyspepsia, and rhinitis) were mild or moderate in intensity, and incidence generally decreased over time. All 3 doses of vardenafil were superior to placebo across all primary efficacy variables and all study time points in a broad range of patients with ED, regardless of etiology or severity. Vardenafil was well tolerated. These results demonstrate that vardenafil provides sustained efficacy with reduced incidence of nuisance side effects over time. High resolution video, medium resolution video, low resolution video.

Aged↗