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Advances in the science of estrogen receptor modulation.

This work details recent advances in the science of estrogen receptor (ER) modulation, with emphasis on the discovery of novel ligands for the ER ligand binding domain (LBD). A detailed examination of structural studies of the ERs is presented with analysis of the impact of such works on contemporary ligand design and the molecular pharmacology of the ER. The various classes of ER modulators are discussed on the basis of stuctural similarities including selective estrogen receptor modulators (SERMs) and 'pure' non-steroidal antiestrogens. Additionally we review the emergence of a novel selective class of modulator which we have termed the selective estrogen receptor subtype modulators (SERSMs) and, in a departure from LBD strategies we examine the discovery of novel peptide inhibitors of the ER which inhibit transcriptional activiation of agonist liganded receptor through interaction with coactivator recruitment proteins, and offer unique insight to the mechanism of action of all classes of ER modulators. Through examination of patent and classical literature we present a thorough and informative cross-section of the contemporary state of the art in this exciting field of pharmaceutical research.

Animals↗

Different mechanisms regulate the monoclonal antibody-induced modulation of CD2, CD3, and CD5 in human lymphocytes.

The CD2, CD3, and CD5 antigens are down-modulated from the cell surface of peripheral blood mononuclear cells after a 24-hr incubation with specific monoclonal antibodies (mAb). Here we show that active (phorbol myristate acetate, phorbol dibutyrate acetate, and mezerein) but not inactive (4 beta-phorbol) tumor-promoting agents inhibit the mAb-induced modulation of CD2 and CD5, but not CD3, without concomitant changes in the surface distribution of these antigens (such as capping). This inhibitory effect is not protein synthesis dependent and is reversed by protein kinase C inhibitors (staurosporine and H-7). The use of cytoskeleton-disrupting agents shows the existence of different cytoskeletal interactions driving the mAb-induced modulation of CD2 and CD5 with respect to CD3. Treatment with cytochalasin D (an agent that inhibits microfilament polymerization) but not colchicine (an agent that inhibits microtubule polymerization) reproduced the effect of TPA on the mAb-induced modulation of CD2, CD3, and CD5. Our results indicate that the mAb-induced modulation of CD2 and CD5 is dependent on microfilament (namely actin) polymerization and PKC activation, while the modulation of CD3 is not.

Antibodies, Monoclonal↗

Modulation of the ethanol-like discriminative stimulus effects of diazepam and phencyclidine by L-type voltage-gated calcium-channel ligands in rats.

RATIONALE: Administration of voltage-gated calcium-channel (VGCC) modulators with ethanol can result in enhancement or attenuation of some behavioral effects of ethanol, including its discriminative stimulus effects. OBJECTIVES: The present study used a drug-discrimination paradigm to characterize modulation of the ethanol-like discriminative stimulus effects of a gamma-amino-butyric acid (GABA)A and N-methyl-D-aspartate (NMDA) ligand by administration of VGCC ligands. METHODS: Two groups of adult male Long-Evans rats were trained to discriminate either 1.0 g/kg ethanol (n=8) or 2.0 g/kg ethanol (n=9) from water under a fixed-ratio (FR) 20 schedule of food presentation. Following training, ethanol substitution tests were conducted with cumulative doses of the GABA(A)-positive modulator diazepam (0.3-10 mg/kg, i.p.) (DZP) and the uncompetitive NMDA antagonist phencyclidine (0.3-5.6 mg/kg, i.p.) (PCP). Next, a single dose of the VGCC antagonist nimodipine, nifedipine, isradipine, or the VGCC agonist (-)-BAY k 8644 (0.3 mg/kg, i.p.) was administered prior to a cumulative DZP or PCP dose-response determination. RESULTS: None of the VGCC modulators produced robust or consistent alterations in the ethanol-like discriminative stimulus effects of DZP in animals trained with either 1.0 g/kg or 2.0 g/kg ethanol. However, the ethanol-like discriminative stimulus effects of PCP were significantly enhanced in the presence of the VGCC antagonists and attenuated in the presence of the agonist in animals trained with 2.0 g/kg ethanol. CONCLUSIONS: Overall, these data show that VGCC modulation is not a robust component of ethanol-like discriminative stimulus effects of DZP in animals trained with 1.0 g/kg or 2.0 g/kg ethanol. However, the ethanol-like effects of PCP, particularly at higher training doses, appear to be modulated by dihydropyridine-sensitive VGCCs.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

Discriminative stimulus effects of positive GABAA modulators and other anxiolytics, sedatives, and anticonvulsants in untreated and diazepam-treated monkeys.

Positive GABAA modulators and other sedatives, anxiolytics, and anticonvulsants were used to evaluate mechanisms underlying the discriminative stimulus effects of midazolam in untreated monkeys and of flumazenil in monkeys treated with diazepam (5.6 mg/kg/day). Positive GABAA modulators at benzodiazepine (e.g., flunitrazepam and abecarnil) and neuroactive steroid sites (e.g., androsterone) substituted for midazolam in all monkeys; the neuroactive steroids dihydroandrosterone and epipregnanolone substituted for midazolam in two of three monkeys. All positive GABAA modulators attenuated flumazenil in diazepam-treated monkeys; doses of flunitrazepam and abecarnil larger than doses substituting for midazolam were required to attenuate flumazenil, whereas doses of neuroactive steroids smaller than doses substituting for midazolam attenuated flumazenil. Drugs with mechanisms that do not predominantly involve allosteric modulation of GABA (e.g., buspirone, ketamine, valproic acid, and diphenhydramine) did not substitute for midazolam or flumazenil. However, valproic acid enhanced the midazolam discriminative stimulus and attenuated the flumazenil discriminative stimulus; diphenhydramine attenuated the midazolam discriminative stimulus. These results suggest that drugs not sharing a mechanism of action with benzodiazepines can modulate the behavioral effects of benzodiazepines. In addition, this study demonstrates that endogenous ligands, presumably by acting at neuroactive steroid sites on the GABAA receptor complex, share discriminative stimulus effects with benzodiazepines. This study also suggests that positive GABAA-modulating neuroactive steroids are especially potent in attenuating behavioral effects that are related to diazepam withdrawal.

Animals↗

Daily treatment with diazepam differentially modifies sensitivity to the effects of gamma-aminobutyric acid(A) modulators on schedule-controlled responding in rhesus monkeys.

The present study examined how daily treatment with the benzodiazepine (BZ) diazepam modifies the effects of positive modulators acting at different sites on the gamma-aminobutyric acid(A) (GABA(A)) receptor complex and negative modulators acting at BZ sites on the receptor complex. GABA(A) modulators were administered alone or in combination with acute or chronic diazepam to rhesus monkeys (n = 4) responding under a multiple fixed ratio (FR/FR) schedule of food presentation and stimulus-shock termination (SST). There was mutual antagonism between the rate-decreasing effects of diazepam (5.6 mg/kg, p.o.) and high efficacy BZ site negative modulators [ethyl beta-carboline-3-carboxylate (beta-CCE), methyl beta-carboline-3-carboxylate (beta-CCM) and methyl-6,7-dimethoxyl-4-ethyl-beta-carboline-3-carboxylate (DMCM)]. Antagonism of beta-CCE, beta-CCM, and DMCM by diazepam was markedly reduced in monkeys receiving diazepam daily. In contrast, daily diazepam treatment enhanced the rate-decreasing effects of Ro 15-4513 (ethyl 8-azido-6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-alpha]-[1,4]benzodiazepine-3-carboxylate) and flumazenil. Chronic diazepam elicited cross-tolerance to the BZ triazolam and not to the barbiturate pentobarbital or the neuroactive steroid pregnanolone. These results suggest that tolerance to the rate-decreasing effects of BZs is not accompanied by cross-tolerance to positive GABA(A) modulators acting at other sites on the receptor complex. Moreover, changes in sensitivity to negative GABA(A) modulators during chronic diazepam treatment appeared to be related to negative efficacy and not clearly related to the precipitation of withdrawal for all drugs. These results indicate that changes in sensitivity to the behavioral effects of drugs that act at different sites on the GABA(A) receptor complex might be especially useful for identifying and characterizing the functional consequences of GABA(A) receptor heterogeneity.

Animals↗

Structural aspects of the functional modules in human protein kinase-C alpha deduced from comparative analyses.

Three-dimensional models of the five functional modules in human protein kinase C alpha (PKC alpha) have been generated on the basis of known related structures. The catalytic region at the C-terminus of the sequence and the N-terminal auto-inhibitory pseudo-substrate have been modeled using the crystal structure complex of cAMP-dependent protein kinase (cAPK) and PKI peptide. While the N-terminal helix of the catalytic region of PKC alpha is predicted to be in a different location compared with cAPK, the C-terminal extension is modeled like that in the cAPK. The predicted permissive phosphorylation site of PKC alpha, Thr 497, is found to be entirely consistent with the mutagenesis studies. Basic Lys and Arg residues in the pseudo-substrate make several specific interactions with acidic residues in the catalytic region and may interact with the permissive phosphorylation site. Models of the two zinc-binding modules of PKC alpha are based on nuclear magnetic resonance and crystal structures of such modules in other PKC isoforms while the calcium phospholipid binding module (C2) is based on the crystal structure of a repeating unit in synaptotagmin I. Phorbol ester binding regions in zinc-binding modules and the calcium binding region in the C2 domain are similar to those in the basis structures. A hypothetical model of the relative positions of all five modules has the putative lipid binding ends of the C2 and the two zinc-binding domains pointing in the same direction and may serve as a basis for further experiments.

Amino Acid Sequence↗

The PedsQL in pediatric rheumatology: reliability, validity, and responsiveness of the Pediatric Quality of Life Inventory Generic Core Scales and Rheumatology Module.

OBJECTIVE: The Pediatric Quality of Life Inventory (PedsQL) is a modular instrument designed to measure health-related quality of life (HRQOL) in children and adolescents ages 2-18 years. The 23-item PedsQL 4.0 Generic Core Scales are multidimensional child self-report and parent proxy-report scales developed as the generic core measure to be integrated with the PedsQL disease-specific modules. The 22-item PedsQL 3.0 Rheumatology Module was designed to measure pediatric rheumatology-specific HRQOL. This study was undertaken to demonstrate the reliability, validity, and responsiveness of the PedsQL 4.0 Generic Core Scales and the PedsQL 3.0 Rheumatology Module in pediatric rheumatology. METHODS: The 4 PedsQL 4.0 Generic Core Scales (physical, emotional, social, and school functioning) and the 5 PedsQL 3.0 Rheumatology Module scales (pain and hurt, daily activities, treatment, worry, and communication) were administered to 231 children and 244 parents (271 subjects accrued overall) recruited from a pediatric rheumatology clinic. RESULTS: Internal consistency reliability for the PedsQL Generic Core total scale score (alpha = 0.91 for child self report, alpha = 0.93 for parent proxy report), physical health summary score (alpha = 0.87 for child self report, alpha = 0.89 for parent proxy report), and psychosocial health summary score (alpha = 0.86 for child self report, alpha = 0.90 for parent proxy report) were acceptable for group comparisons. The Rheumatology Module scales also demonstrated acceptable reliability for group comparisons (alpha = 0.75-0.86 for child self report, alpha = 0.82-0.91 for parent proxy report). Validity was demonstrated using the known-groups method. The PedsQL distinguished between healthy children and children with rheumatic diseases as a group. The responsiveness of the PedsQL was demonstrated through patient change over time as a result of clinical intervention. CONCLUSION: The results demonstrate the reliability, validity, and responsiveness of the PedsQL 4.0 Generic Core Scales and the PedsQL 3.0 Rheumatology Module in pediatric rheumatology.

Adolescent↗

Inter-beat intervals of cardiac-cell aggregates during exposure to 2.45 GHz CW, pulsed, and square-wave-modulated microwaves.

Inter-beat intervals of aggregated cardiac cells from chicken embryos were studied during 190 s exposures to 2.45 GHz microwaves in an open-ended coaxial device. Averaged specific-absorption rates (SARs) and modulation conditions were 1.2-86.9 W/kg continuous-wave (CW), 1.2-12.2 W/kg pulse modulation (PW, duty cycle approximately 11%), and 12.0-43.5 W/kg square-wave modulation (duty cycle = 50%). The inter-beat interval decreased during microwave exposures at 42.0 W/kg and higher when CW or square-wave modulation was used, which is consistent with established effects of elevated temperatures. However, increases in the inter-beat interval during CW exposures at 1.2-12.2 W/kg, and decreases in the inter-beat interval after PW exposures at 8.4-12.2 W/kg, are not consistent with simple thermal effects. Analysis of variance indicated that SAR, modulation, and the modulation-SAR interaction were all significant factors in altering the inter-beat interval. The latter two factors indicated that the cardiac cells were affected by athermal as well as thermal effects of microwave exposure.

Animals↗

The conserved C-terminal I/LWEQ module targets Talin1 to focal adhesions.

The cytoskeletal protein Talin1 is a critical link between integrins and the actin cytoskeleton, where it is required for the structural and signaling functions of integrin-containing adhesion complexes. However, the elements in Talin1 that are responsible for localizing it to adhesion complexes are not known. In this report we have used a series of constructs based on the modular structure of Talin1 to determine the structural elements that specify the subcellular localization of Talin1. We show that the conserved actin-binding I/LWEQ module at the C-terminus of Talin1 is necessary and sufficient for targeting to focal adhesion complexes. We also used truncation and site-directed mutagenesis to demonstrate that this novel targeting function correlates with, but is separable from, the actin-binding properties of the Talin1 I/LWEQ module. In addition, we have shown that focal adhesion targeting, unlike actin binding, is not conserved among I/LWEQ module proteins. Finally, we have demonstrated that the subcellular localization of the Talin1 I/LWEQ module is regulated by an intrasteric interaction with an upstream alpha-helix, suggesting that both the actin binding and adhesion-targeting elements are masked in full-length Talin1. Our results define a novel role for the I/LWEQ module as the primary adhesion-complex targeting determinant of Talin1 and suggest that pathways that can relieve inhibition of I/LWEQ module function will be important for regulating the structural and signaling properties of adhesion complexes.

Actins↗

Patterns of anthracycline retention modulation in human tumor cells.

Laser excitation of cellular doxorubicin and daunomycin content (with or without incubation in the presence of efflux blockers such as phenothiazines or verapamil) was studied in cells from leukemic peripheral blood, bone marrow aspirates, and ascites and pleural fluid of solid tumor patients. Selected examples are presented to show that heterogeneity in cellular anthracycline retention as well as sensitivity to efflux modulators is seen in human tumor cells. Several tumor subpopulations differing in their cellular retention of anthracyclines or sensitivity to modulators were seen. In serial tumor samples from patients (pre- and post-treatment with anthracycline-containing protocols), initial drug retention and sensitivity to efflux modulators was followed by lack of drug retention and insensitivity to modulators. The present study shows that in view of the variables encountered in drug-retention characteristics and sensitivity to efflux modulators, one needs to screen tumor samples before recommending use of any particular transport modulator to enhance drug retention and sensitivity of drug-resistant cells.

Bone Marrow↗

Modulation of P-glycoprotein but not MRP1- or BCRP-mediated drug resistance by LY335979.

Our study examines the ability of LY335979 (Zosuquidar trihydrochloride) to modulate 3 distinct ABC transporters that are mechanisms of drug resistance: P-glycoprotein (Pgp, ABCB1), multidrug resistance associated protein (MRP1, ABCC2) and breast cancer resistance protein (BCRP, ABCG2). Pgp-mediated resistance can be modulated by coadministration with the highly potent, selective inhibitor, LY335979. Modulation of resistance by mitoxantrone and vinorelbine, 2 drugs used to treat certain solid tumors, was examined in a 3-day cytotoxicity assay using a panel of HL60 leukemia cell lines or MCF-7 breast cancer transfectants. LY335979, at 0.5 microM, substantially reversed mitoxantrone resistance and fully reversed vinorelbine resistance of Pgp-expressing HL60/Vinc cells. However, LY335979 did not modulate drug resistance in the MRP1-expressing HL60/ADR or drug-sensitive parental HL60 cells. To ascertain if LY335979 modulates BCRP-mediated drug resistance, the sensitivity of 26-fold mitoxantrone resistant, BCRP-transfected MCF-7 cells was evaluated. Addition of 5 microM LY335979, a concentration approximately 100-fold higher than the affinity of Pgp, had little to no effect on the BCRP transfectant. [(125)I]Iodomycin photolabeled Pgp in CEM/VLB(100) membranes and was inhibited by 5 microM LY335979 and GF120918. No photolabeling of MRP or BCRP occurred in H69AR or MCF-7/BCRP membranes, respectively. These results further demonstrate that LY335979 is highly specific for Pgp and does not modulate MRP1- or BCRP-mediated resistance and can be used in combination with mitoxantrone and vinorelbine in tumor cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Evaluation of S9788 as a potential modulator of drug resistance against human tumour sublines expressing differing resistance mechanisms in vitro.

Significant activity has been identified using S9788, a triazineaminopiperidine derivative, as a new modulator of multi-drug resistance against a series of drug-resistant human tumour-cell lines in vitro. Maximal non-cytotoxic concentrations (i.e., those resulting in < or = 10% cytotoxicity) of S9788 or verapamil were tested in combination with vinblastine, Adriamycin or vincristine and cytotoxicity was evaluated using a clonogenic assay, or the metabolic dye reduction MTT assay, or by monitoring growth inhibition. Under these conditions, the extent of resistance modulation by verapamil and by S9788 was comparable in the various tumour cell lines tested, although a definite concentration-dependent modulation was noted with both compounds. The highest dose-modification factors were noted in the highly vinblastine-resistant classic multi-drug-resistant subline CEM/VLB100, although resistance reversal was only partial. Resistance modulation by both verapamil and S9788 was noted in 4 drug-selected resistant sublines and 4 "intrinsically" resistant human tumour cell lines, which all exhibited significant P-glycoprotein expression. In contrast, in 2 drug-resistant human tumour sublines (GLC4/ADR and CEM/VM-1) characterized by altered topoisomerase-II activity and proving to be P-glycoprotein-negative, no resistance modulation relative to parental cells was observed. These data are consistent with the proposal that resistance modulation is mediated by interaction between S9788 and P-glycoprotein and support its clinical evaluation in patients with P-glycoprotein-positive tumours.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Varieties of modules: kinds, levels, origins, and behaviors.

This article began as a review of a conference, organized by Gerhard Schlosser, entitled "Modularity in Development and Evolution." The conference was held at, and sponsored by, the Hanse Wissenschaftskolleg in Delmenhorst, Germany in May, 2000. The article subsequently metamorphosed into a literature and concept review as well as an analysis of the differences in current perspectives on modularity. Consequently, I refer to general aspects of the conference but do not review particular presentations. I divide modules into three kinds: structural, developmental, and physiological. Every module fulfills none, one, or multiple functional roles. Two further orthogonal distinctions are important in this context: module-kinds versus module-variants-of-a-kind and reproducer versus nonreproducer modules. I review criteria for individuation of modules and mechanisms for the phylogenetic origin of modularity. I discuss conceptual and methodological differences between developmental and evolutionary biologists, in particular the difference between integration and competition perspectives on individualization and modular behavior. The variety in views regarding modularity presents challenges that require resolution in order to attain a comprehensive, rather than a piecemeal and fragmentary, evolutionary developmental biology. J. Exp. Zool. (Mol. Dev. Evol.) 291:116-129, 2001.

Adaptation, Physiological↗

A systematic analysis of a flow-switching modulator for comprehensive two-dimensional gas chromatography.

A simple flow-switching device has been designed for use as a comprehensive two-dimensional gas chromatography modulator. The device is constructed from fused silica tubing, t-unions, and a solenoid valve. A series of experiments were conducted to determine the influence of primary flow, secondary flow, modulation time, and device dimensions on the performance of the modulator. The flow-switching device was found to produce pulses with widths near the theoretical minimum. High-performance was maintained over a wide range of modulation times. The flow-switching device did not introduce extra broadening along the primary retention axis. However, the modulator performance was optimal only over a narrow range of primary to secondary flow ratios. The ideal flow ratio is determined by the dimensions of the tubes that connect the t-unions. A simple flow resistance model has been developed that can predict the dimensions that will produce optimal results for a specified primary to secondary flow ratio. Thus, it is possible to construct a device that operates near the theoretical limit without numerous alterations. Under optimal conditions, the flow switching modulator generates peaks that are narrower than those produced by a diaphragm valve.

Journal Article↗

Session-long modulations of accumbal firing during sucrose-reinforced operant behavior.

The nucleus accumbens is involved in the selection and expression of motivated behaviors. Attempts to understand how activity of single neurons in the accumbens relates to behavior have largely concentrated on brief modulations in accumbal firing that occur in the seconds around events during operant sessions. However, a small number of studies have reported modulations that last the entire duration of a behavioral session. In all of these reports, the operant session was a drug self-administration session. The present study tested the hypothesis that session-long modulations, like phasic firing patterns, are components of normal accumbal activity during periods of instrumental behavior. Eight rats were chronically implanted (unilaterally) with microwire arrays in the nucleus accumbens, and trained to lever press on a Fixed-Ratio 1 schedule of sucrose reinforcement. Activity of 51 single units was recorded, and both session-long increases (n = 14) and session-long decreases (n = 13) were observed. These findings show that session-long modulations are a normal component of the response of accumbal neurons during periods of operant behavior. Moreover, although session-long modulations during cocaine self-administration sessions might reflect pharmacological actions, aspects of the modulations might additionally or alternatively correspond to afferent-driven responses. Further characterization of the firing patterns may elucidate novel mechanisms that mediate accumbal contributions to behavior.

Animals↗

Specific regulation of male rat liver cytosolic estrogen receptor by the modulator of the glucocorticoid receptor.

Modulator is a novel low-molecular-weight organic compound that regulates activities of glucocorticoid and mineralocorticoid receptors as well as protein kinase C. In this study we show that male rat liver cytosolic estrogen receptor activation is inhibited by modulator in a dose-dependent manner. Fifty percent inhibition is obtained with 1 unit/ml modulator purified from bovine liver which is within the physiological concentration for modulator. However, sheep uterine cytosolic estrogen and androgen receptors are insensitive to regulation by modulator. Exogenous sodium molybdate treatment inhibits activation of all of these receptors of liver or uterus origin in an identical manner, further differentiating the effects of modulator and the molybdate anion.

Adrenalectomy↗

Modular structure of neuronal nitric oxide synthase: localization of the arginine binding site and modulation by pterin.

A putative dihydrofolate reductase (DHFR) module has been identified in neuronal nitric oxide synthase, consisting of amino acids 558-721, and is proposed to be the site of tetrahydrobiopterin (BH4) binding. This polypeptide has been expressed in E. coli as a fusion protein with glutathione S-transferase (GST), using the plasmid pGEX-4T1. The protein binds N omega-nitro-L-arginine (NNA) tightly, but this binding is not stimulated by BH4. cDNAs for Module II (residues 220-557) and Module III (residues 220-721) have been expressed as fusion proteins with GST. Module II does not bind NNA. However, Module III does bind NNA and binding is significantly stimulated by BH4. These observations are taken as strong evidence that the DHFR module contains the L-arginine binding site and, presumably, the BH4 binding site by analogy to its homology with DHFR, but that tight binding of BH4 requires amino acids 220-577.

Amino Acid Oxidoreductases↗

Calcium modulated signaling site in type 2 rod outer segment membrane guanylate cyclase (ROS-GC2).

The ROS-GC subfamily of membrane guanylate cyclases is at present represented by two members: ROS-GC1 and ROS-GC2. A unique functional feature of this subfamily is that it is intracellularly modulated in low Ca2+ concentration by calmodulin-like Ca(2+)-binding proteins termed GCAPs, 1 and 2, and the modulation is consistent with its linkage to phototransduction. The present study shows that: (1) GCAP2 is a specific modulator of ROS-GC2; (2) through systematic remodeling of ROS-GC modules, the study also shows that the modulated domain resides within the amino acid segment 736-1020. This domain is distinct form the corresponding GCAP1-modulated ROS-GC1 domain. Thus, GCAP1 and GCAP2 act through different ROS-GCs and through two different cyclase domains.

Animals↗