Structure of a D2 dopamine receptor-G-protein complex in a lipid membrane.

The D2 dopamine receptor (DRD2) is a therapeutic target for Parkinson's disease1 and antipsychotic drugs2. DRD2 is activated by the endogenous neurotransmitter dopamine and synthetic agonist drugs such as bromocriptine3, leading to stimulation of Gi and inhibition of adenylyl cyclase. Here we used cryo-electron microscopy to elucidate the structure of an agonist-bound activated DRD2-Gi complex reconstituted into a phospholipid membrane. The extracellular ligand-binding site of DRD2 is remodelled in response to agonist binding, with conformational changes in extracellular loop 2, transmembrane domain 5 (TM5), TM6 and TM7, propagating to opening of the intracellular Gi-binding site. The DRD2-Gi structure represents, to our knowledge, the first experimental model of a G-protein-coupled receptor-G-protein complex embedded in a phospholipid bilayer, which serves as a benchmark to validate the interactions seen in previous detergent-bound structures. The structure also reveals interactions that are unique to the membrane-embedded complex, including helix 8 burial in the inner leaflet, ordered lysine and arginine side chains in the membrane interfacial regions, and lipid anchoring of the G protein in the membrane. Our model of the activated DRD2 will help to inform the design of subtype-selective DRD2 ligands for multiple human central nervous system disorders.

Leveraging nonstructural data to predict structures and affinities of protein-ligand complexes.

Over the past five decades, tremendous effort has been devoted to computational methods for predicting properties of ligands-i.e., molecules that bind macromolecular targets. Such methods, which are critical to rational drug design, fall into two categories: physics-based methods, which directly model ligand interactions with the target given the target's three-dimensional (3D) structure, and ligand-based methods, which predict ligand properties given experimental measurements for similar ligands. Here, we present a rigorous statistical framework to combine these two sources of information. We develop a method to predict a ligand's pose-the 3D structure of the ligand bound to its target-that leverages a widely available source of information: a list of other ligands that are known to bind the same target but for which no 3D structure is available. This combination of physics-based and ligand-based modeling improves pose prediction accuracy across all major families of drug targets. Using the same framework, we develop a method for virtual screening of drug candidates, which outperforms standard physics-based and ligand-based virtual screening methods. Our results suggest broad opportunities to improve prediction of various ligand properties by combining diverse sources of information through customized machine-learning approaches.

An allosteric modulator binds to a conformational hub in the ß2 adrenergic receptor.

Most drugs acting on G-protein-coupled receptors target the orthosteric binding pocket where the native hormone or neurotransmitter binds. There is much interest in finding allosteric ligands for these targets because they modulate physiologic signaling and promise to be more selective than orthosteric ligands. Here we describe a newly developed allosteric modulator of the ß2-adrenergic receptor (ß2AR), AS408, that binds to the membrane-facing surface of transmembrane segments 3 and 5, as revealed by X-ray crystallography. AS408 disrupts a water-mediated polar network involving E1223.41 and the backbone carbonyls of V2065.45 and S2075.46. The AS408 binding site is adjacent to a previously identified molecular switch for ß2AR activation formed by I3.40, P5.50 and F6.44. The structure reveals how AS408 stabilizes the inactive conformation of this switch, thereby acting as a negative allosteric modulator for agonists and positive allosteric modulator for inverse agonists.

Developmental Monitoring and Referral for Low-Income Children Served by WIC: Program Development and Implementation Outcomes.

OBJECTIVE: To develop, implement, and assess implementation outcomes for a developmental monitoring and referral program for children in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). METHODS: Based on Centers for Disease Control and Prevention's Learn the Signs. Act Early. campaign, the program was developed and replicated in two phases at 20 demographically diverse WIC clinics in eastern Missouri. Parents were asked to complete developmental milestone checklists for their children, ages 2 months to 4 years, during WIC eligibility recertification visits; WIC staff referred children with potential concerns to their healthcare providers for developmental screening. WIC staff surveys and focus groups were used to assess initial implementation outcomes. RESULTS: In both phases, all surveyed staff (n = 46) agreed the program was easy to use. Most (≥ 80%) agreed that checklists fit easily into clinic workflow and required ≤ 5 min to complete. Staff (≥ 55%) indicated using checklists with ≥ 75% of their clients. 92% or more reported referring one or more children with potential developmental concerns. According to 80% of staff, parents indicated checklists helped them learn about development and planned to share them with healthcare providers. During the second phase, 18 of 20 staff surveyed indicated the program helped them learn when to refer children and how to support parents, and 19 felt the program promoted healthy development. Focus groups supported survey findings, and all clinics planned to sustain the program. CONCLUSIONS: Initial implementation outcomes supported this approach to developmental monitoring and referral in WIC. The program has potential to help low-income parents identify possible concerns and access support.

Structure-guided development of selective M3 muscarinic acetylcholine receptor antagonists.

Drugs that treat chronic obstructive pulmonary disease by antagonizing the M3 muscarinic acetylcholine receptor (M3R) have had a significant effect on health, but can suffer from their lack of selectivity against the M2R subtype, which modulates heart rate. Beginning with the crystal structures of M2R and M3R, we exploited a single amino acid difference in their orthosteric binding pockets using molecular docking and structure-based design. The resulting M3R antagonists had up to 100-fold selectivity over M2R in affinity and over 1,000-fold selectivity in vivo. The crystal structure of the M3R-selective antagonist in complex with M3R corresponded closely to the docking-predicted geometry, providing a template for further optimization.

Structure-based discovery of selective positive allosteric modulators of antagonists for the M2 muscarinic acetylcholine receptor.

Subtype-selective antagonists for muscarinic acetylcholine receptors (mAChRs) have long been elusive, owing to the highly conserved orthosteric binding site. However, allosteric sites of these receptors are less conserved, motivating the search for allosteric ligands that modulate agonists or antagonists to confer subtype selectivity. Accordingly, a 4.6 million-molecule library was docked against the structure of the prototypical M2 mAChR, seeking molecules that specifically stabilized antagonist binding. This led us to identify a positive allosteric modulator (PAM) that potentiated the antagonist N-methyl scopolamine (NMS). Structure-based optimization led to compound '628, which enhanced binding of NMS, and the drug scopolamine itself, with a cooperativity factor (α) of 5.5 and a KB of 1.1 µM, while sparing the endogenous agonist acetylcholine. NMR spectral changes determined for methionine residues reflected changes in the allosteric network. Moreover, '628 slowed the dissociation rate of NMS from the M2 mAChR by 50-fold, an effect not observed at the other four mAChR subtypes. The specific PAM effect of '628 on NMS antagonism was conserved in functional assays, including agonist stimulation of [35S]GTPγS binding and ERK 1/2 phosphorylation. Importantly, the selective allostery between '628 and NMS was retained in membranes from adult rat hypothalamus and in neonatal rat cardiomyocytes, supporting the physiological relevance of this PAM/antagonist approach. This study supports the feasibility of discovering PAMs that confer subtype selectivity to antagonists; molecules like '628 can convert an armamentarium of potent but nonselective GPCR antagonist drugs into subtype-selective reagents, thus reducing their off-target effects.

A randomized controlled trial to evaluate outcomes of a workplace self-management intervention and an intensive monitoring intervention.

The purpose of this study was to determine and compare outcomes of two voluntary workplace health management methods: an adapted worksite self-management (WSM) approach and an intensive health monitoring (IM) approach. Research participants were randomly assigned to either the WSM group or the IM group by a computer-generated list (n = 180; 92 WSM and 88 IM). Participants completed baseline, 3 and 12-month follow-up surveys. Individuals receiving workplace WSM and IM improved in self-efficacy and nearly all health behaviors and health status variables after the intervention, compared to before the intervention. Individuals in the WSM group improved in depression symptoms at 3 and 12 months (P < 0.0001, P < 0.0001), and individuals in the IM group did not improve at either time period (P < 0.1488, P < 0.0521). Participants in the WSM group reported more improvement in physical activity and energy, health interfering less with personal life and daily activities and fewer depression symptoms at follow up, compared to participants in the IM group. This study provided additional support for worksite-based health promotion programs to promote healthy lifestyles and improve health status, and documented effectiveness of both methods, with superior performance and greater scalability for the WSM program.

Discovery of positive allosteric modulators and silent allosteric modulators of the µ-opioid receptor.

µ-Opioid receptors are among the most studied G protein-coupled receptors because of the therapeutic value of agonists, such as morphine, that are used to treat chronic pain. However, these drugs have significant side effects, such as respiratory suppression, constipation, allodynia, tolerance, and dependence, as well as abuse potential. Efforts to fine tune pain control while alleviating the side effects of drugs, both physiological and psychological, have led to the development of a wide variety of structurally diverse agonist ligands for the µ-opioid receptor, as well as compounds that target κ- and δ-opioid receptors. In recent years, the identification of allosteric ligands for some G protein-coupled receptors has provided breakthroughs in obtaining receptor subtype-selectivity that can reduce the overall side effect profiles of a potential drug. However, positive allosteric modulators (PAMs) can also have the specific advantage of only modulating the activity of the receptor when the orthosteric agonist occupies the receptor, thus maintaining spatial and temporal control of receptor signaling in vivo. This second advantage of allosteric modulators may yield breakthroughs in opioid receptor research and could lead to drugs with improved side-effect profiles or fewer tolerance and dependence issues compared with orthosteric opioid receptor agonists. Here, we describe the discovery and characterization of µ-opioid receptor PAMs and silent allosteric modulators, identified from high-throughput screening using a ß-arrestin-recruitment assay.

Act Healthy: promoting health behaviors and self-efficacy in the workplace.

Chronic health conditions and multiple health risk factors afflict Americans and burden employers, but effective, affordable, workplace-based health promotion interventions have not been widely implemented. This is the first study to adapt the empirically validated Chronic Disease Self-Management Program for a general employee population in a workplace setting with an emphasis on disease prevention and health promotion. A quasi-experimental, wellness standard of care comparison, prospective cohort design was used among employee participants at a large University employer. Ninety-one individuals participated in the program. Participants reported significantly increased health behavior frequency and self-efficacy after the intervention, compared with their pre-intervention scores, and improvements were sustained at 3-month follow-up [self-rated abilities for health practices scale (SRA): F = 30.89, P < 0.001; health promoting lifestyle profile-II (HPLP-II): F = 36.30 P < 0.001]. Individuals in the intervention group reported improved self-efficacy and health behaviors compared with the wellness standard of care comparison group at post intervention (SRA: F = 12.45, P < 0.001; HPLP-II: F = 25.28, P < 0.001). Adapting lay-facilitated self-management for the workplace offers promise as a replicable, scalable, affordable model for culture change in organizations.

Increased agonist affinity at the µ-opioid receptor induced by prolonged agonist exposure.

Prolonged exposure to high-efficacy agonists results in desensitization of the µ-opioid receptor (MOR). Desensitized receptors are thought to be unable to couple to G-proteins, preventing downstream signaling; however, the changes to the receptor itself are not well characterized. In the current study, confocal imaging was used to determine whether desensitizing conditions cause a change in agonist-receptor interactions. Using rapid solution exchange, the binding kinetics of fluorescently labeled opioid agonist, dermorphin Alexa594 (derm A594), to MORs was measured in live cells. The affinity of derm A594 binding increased after prolonged treatment of cells with multiple agonists that are known to cause receptor desensitization. In contrast, binding of a fluorescent antagonist, naltrexamine Alexa594, was unaffected by similar agonist pretreatment. The increased affinity of derm A594 for the receptor was long-lived and partially reversed after a 45 min wash. Treatment of the cells with pertussis toxin did not alter the increase in affinity of the derm A594 for MOR. Likewise, the affinity of derm A594 for MORs expressed in mouse embryonic fibroblasts derived from arrestin 1 and 2 knock-out animals increased after treatment of the cells with the desensitization protocol. Thus, opioid receptors were "imprinted" with a memory of prior agonist exposure that was independent of G-protein activation or arrestin binding that altered subsequent agonist-receptor interactions. The increased affinity suggests that acute desensitization results in a long-lasting but reversible conformational change in the receptor.

Synthesis and evaluation of 4-substituted piperidines and piperazines as balanced affinity µ opioid receptor (MOR) agonist/δ opioid receptor (DOR) antagonist ligands.

In this letter, we describe a series of 4-substituted piperidine and piperazine compounds based on tetrahydroquinoline 1, a compound that shows balanced, low nanomolar binding affinity for the mu opioid receptor (MOR) and the delta opioid receptor (DOR). We have shown that by changing the length and flexibility profile of the side chain in this position, binding affinity is improved at both receptors by a significant degree. Furthermore, several of the compounds described herein display good efficacy at MOR, while simultaneously displaying DOR antagonism. The MOR agonist/DOR antagonist has shown promise in the reduction of negative side effects displayed by selective MOR agonists, namely the development of dependence and tolerance.

The relationship between the medical home and unmet needs for children with autism spectrum disorders.

The purpose of this study was to examine the relationship between having access to a medical home and unmet needs for specialty care services for children with autism spectrum disorders (ASD). Parents of children enrolled in a national autism registry were invited to complete an online Access to Care Questionnaire. The resulting sample consisted of 371 parents-child dyads. Bivariate and hierarchical regression analyses were conducted to determine whether having a medical home was associated with the number of unmet needs for specialty care. Less than one in five children with ASD had a medical home (18.9%). Nearly all parents reported that their child had a personal doctor or nurse as well as a usual source of care, but less than one-third received coordinated care (29.9%) and less than one-half received family-centered care (47.1%). Many children had unmet needs (63%), and the highest unmet need was for behavioral therapy. Having a medical home was associated with fewer unmet specialty care needs, even after demographic, child and family characteristics were taken into account. Children with ASD who have a medical home are more likely to have adequate access to needed services. Unfortunately, relatively few children have a medical home that includes family-centered and coordinated care. Enhancements in the delivery of primary care for children with ASD may make a real difference in access to needed specialty care services, potentially improving child and family outcomes.

Constrained catecholamines gain ß2AR selectivity through allosteric effects on pocket dynamics.

G protein-coupled receptors (GPCRs) within the same subfamily often share high homology in their orthosteric pocket and therefore pose challenges to drug development. The amino acids that form the orthosteric binding pocket for epinephrine and norepinephrine in the ß1 and ß2 adrenergic receptors (ß1AR and ß2AR) are identical. Here, to examine the effect of conformational restriction on ligand binding kinetics, we synthesized a constrained form of epinephrine. Surprisingly, the constrained epinephrine exhibits over 100-fold selectivity for the ß2AR over the ß1AR. We provide evidence that the selectivity may be due to reduced ligand flexibility that enhances the association rate for the ß2AR, as well as a less stable binding pocket for constrained epinephrine in the ß1AR. The differences in the amino acid sequence of the extracellular vestibule of the ß1AR allosterically alter the shape and stability of the binding pocket, resulting in a marked difference in affinity compared to the ß2AR. These studies suggest that for receptors containing identical binding pocket residues, the binding selectivity may be influenced in an allosteric manner by surrounding residues, like those of the extracellular loops (ECLs) that form the vestibule. Exploiting these allosteric influences may facilitate the development of more subtype-selective ligands for GPCRs.

Consultative care coordination through the medical home for CSHCN: a randomized controlled trial.

The purpose of this study was to examine the impact of a care coordination intervention aimed at improving the medical home for children with special health care needs (CSHCN). 100 CSHCN referred by a Medicaid managed care plan were randomly assigned to a care coordination intervention or to a wait list comparison group that received standard care. For the intervention group, a care coordinator supported the medical home by consulting with primary care providers at multiple practices to develop an integrated, individualized plan to meet child and family needs. During the second phase of the study, the wait list comparison group received the 6-month intervention. At the end of 12 months, the two groups were combined to examine within subject differences (n = 61). Compared to the control group, participants in the initial intervention group reported a decreased need for information and improved satisfaction with mental health services and specialized therapies. This effect was replicated when the wait list control group received the intervention. Additional benefits were observed in the within subject analysis, including a decline in unmet needs, improved satisfaction with specialty care and care coordination, and improved ratings of child health and family functioning. This intervention improved outcomes for CSHCN and their families by supporting the efforts of primary care physicians to provide comprehensive and coordinated care through the medical home. The consulting care coordinator may provide an efficient and cost effective approach to enhancing the quality of care for CSHCN.

Binding pathway determines norepinephrine selectivity for the human ß1AR over ß2AR.

Beta adrenergic receptors (ßARs) mediate physiologic responses to the catecholamines epinephrine and norepinephrine released by the sympathetic nervous system. While the hormone epinephrine binds ß1AR and ß2AR with similar affinity, the smaller neurotransmitter norepinephrine is approximately tenfold selective for the ß1AR. To understand the structural basis for this physiologically important selectivity, we solved the crystal structures of the human ß1AR bound to an antagonist carazolol and different agonists including norepinephrine, epinephrine and BI-167107. Structural comparison revealed that the catecholamine-binding pockets are identical between ß1AR and ß2AR, but the extracellular vestibules have different shapes and electrostatic properties. Metadynamics simulations and mutagenesis studies revealed that these differences influence the path norepinephrine takes to the orthosteric pocket and contribute to the different association rates and thus different affinities.

Differential modulation of mu-opioid receptor signaling to adenylyl cyclase by regulators of G protein signaling proteins 4 or 8 and 7 in permeabilised C6 cells is Galpha subtype dependent.

Regulators of G protein signaling (RGS) proteins act as GTPase-accelerating protein to negatively modulate G protein signaling and are defined by a conserved RGS domain with considerable amino acid diversity. To determine the effects of specific, purified RGS proteins on mu-opioid signaling, C6 cells stably expressing a mu-opioid receptor were rendered permeable to proteins by treatment with digitonin. Mu-opioid inhibition of forskolin-stimulated adenylyl cyclase by [D-Ala(2),N-Me-Phe(4),Gly-ol]-enkephalin (DAMGO), a mu-specific opioid peptide, remained fully intact in permeabilized cells. Purified RGS domain of RGS4 added to permeabilized cells resulted in a twofold loss in DAMGO potency but had no effect in cells expressing RGS-insensitive G proteins. The inhibitory effect of DAMGO was reduced to the same extent by purified RGS4 and RGS8. In contrast, the RGS domain of RGS7 had no effect and inhibited the action of RGS8 as a result of weak physical association with Galphai2 and minimal GTPase-accelerating protein activity in C6 cell membranes. These data suggest that differences in conserved RGS domains of specific RGS proteins contribute to differential regulation of opioid signaling to adenylyl cyclase and that a permeabilized cell model is useful for studying the effects of specific RGS proteins on aspects of G protein-coupled receptor signaling.

Structure and selectivity engineering of the M1 muscarinic receptor toxin complex.

Muscarinic toxins (MTs) are natural toxins produced by mamba snakes that primarily bind to muscarinic acetylcholine receptors (MAChRs) and modulate their function. Despite their similar primary and tertiary structures, MTs show distinct binding selectivity toward different MAChRs. The molecular details of how MTs distinguish MAChRs are not well understood. Here, we present the crystal structure of M1AChR in complex with MT7, a subtype-selective anti-M1AChR snake venom toxin. The structure reveals the molecular basis of the extreme subtype specificity of MT7 for M1AChR and the mechanism by which it regulates receptor function. Through in vitro engineering of MT7 finger regions that was guided by the structure, we have converted the selectivity from M1AChR toward M2AChR, suggesting that the three-finger fold is a promising scaffold for developing G protein-coupled receptor modulators.

A longitudinal comparison of consumer-directed and agency-directed personal assistance service programmes among persons with physical disabilities.

PURPOSE: To compare outcomes for persons who were enrolled in an agency-directed personal assistance services (PAS) programme and then changed to a consumer-directed PAS programme. METHOD: A convenience sample was used for this longitudinal study. In-home interviews were conducted by a trained data collector from April 2000 to December 2001. RESULTS: Participants reported more satisfaction and safety with personal assistance, and fewer unmet needs after receiving consumer-directed services than after receiving agency-directed services. Other variables related to outcomes included race and ethnicity, employment, functional status, unmet needs, and the level of confidence in obtaining help if assistance is unavailable. Participants (74%) also reported high rates of unmet needs in the past month. CONCLUSIONS: Consumer-directed PAS enhances outcomes for many persons with disabilities. Self-reported outcomes are affected by many factors that could be addressed in PAS program development.

Evaluation of a consumer-personal assistant training project.

PURPOSE: This study evaluated a personal assistance services (PAS) training programme that aimed to improve the consumer and personal assistant relationship and increase consumer and personal assistant knowledge on health and wellness issues. METHOD: A total of 87 consumers and 53 personal assistants were enrolled in this longitudinal intervention study. Consumers and personal assistants in the intervention group participated in a six-hour in-person PAS training programme. RESULTS: Consumers and personal assistants who participated in the training had increased knowledge at both three and six months post-training compared to consumers and personal assistants who were in the non-treatment group. There were no differences in consumer/personal assistant relationship variables. CONCLUSIONS: Future studies should examine the impact of PAS training programmes on health behaviours needed to decrease secondary conditions.