Jennifer M. Reingle Gonzalez

Role of dimer interface in activation and desensitization in AMPA receptors.

The conversion of chemical to electrical signals by the AMPA receptors is the key step by which these proteins control cognitive and motor responses. Here, we have used luminescence resonance energy transfer (LRET) to gain insight into the conformational changes induced by glutamate binding in the agonist-binding domain in functional AMPA receptors expressed in oocytes and HEK-293 cells. The LRET-based distances indicate that the interface between the upper lobes of the agonist-binding domain within a dimer is in a decoupled state in the unligated Apo state of the receptor. Agonist binding results in the formation of the dimer interface in the open-channel form of the receptor. In the continued presence of glutamate when the receptor is primarily in the desensitized state, the dimer interface is decoupled, confirming that the decoupling of the dimer interface leads to channel closure. The LRET distances also indicate that the dimer interface is preformed before activation in the L484Y mutation and also is formed in the antagonist (ZK200775)-bound form of the AMPA receptor. These results suggests that, although the preformation of the interface is not sufficient to drive channel activation, it could play a role in the energetics of activation and hence modulation of the receptor by auxiliary proteins or small molecules.

Subunit arrangement in N-methyl-D-aspartate (NMDA) receptors.

N-Methyl-d-aspartate (NMDA) receptors, the main mediators of excitatory synaptic transmission, are heterotetrameric receptors. Typically, glycine binding NR1 subunits co-assemble with glutamate binding NR2 subunits to form a functional receptor. Here we have used luminescence resonance energy transfer (LRET) investigations to establish the specific configuration in which these subunits assemble to form the functional tetramer and show that the dimer of dimers structure is formed by the NR1 subunits assembling diagonally to each other. The distances measured by LRET are consistent with the NMDA structure predicted based on cross-linking investigations and on the structure of the full-length α-amino-5-methyl-3-hydroxy-4-isoxazole propionic acid (AMPA) receptor structure (1). Additionally, the LRET distances between the NR1 and NR2A subunits within a dimer measured in the desensitized state of the receptor are longer than the distances in the previously published crystal structure of the isolated ligand binding domain of NR1-NR2A. Because the dimer interface in the isolated ligand binding domain crystallizes in the open channel structure, the longer LRET distances would be consistent with the decoupling of the dimer interface in the desensitized state. This is similar to what has been previously observed for the AMPA subtype of the ionotropic glutamate receptors, suggesting a similar mechanism for desensitization in the two subtypes of the glutamate receptor.

Conformational Changes at the Agonist Binding Domain of the N-Methyl-d-Aspartic Acid Receptor

The conformational changes in the agonist binding domain of the glycine-binding GluN1 and glutamate-binding GluN2A subunits of the N-methyl d-aspartic acid receptor upon binding agonists of varying efficacy have been investigated by luminescence resonance energy transfer (LRET) measurements. The LRET-based distances indicate a cleft closure conformational change at the GluN1 subunit upon binding agonists; however, no significant changes in the cleft closure are observed between partial and full agonists. This is consistent with the previously reported crystal structures for the isolated agonist binding domain of this receptor. Additionally, the LRET-based distances show that the agonist binding domain of the glutamate-binding GluN2A subunit exhibits a graded cleft closure with the extent of cleft closure being proportional to the extent of activation, indicating that the mechanism of activation in this subunit is similar to that of the glutamate binding α-amino-5-methyl-3-hydroxy-4-isoxazole propionate and kainate subtypes of the ionotropic glutamate receptors.

LRET investigations of conformational changes in the ligand binding domain of a functional AMPA receptor.

The structural investigations using the soluble ligand binding domain of the AMPA subtype of the glutamate receptor have provided invaluable insight into the mechanistic pathway by which agonist binding to this extracellular domain mediates the formation of cation-selective channels in this protein. These structures, however, are in the absence of the transmembrane segments, the primary functional component of the protein. Here, we have used a modified luminescence resonance energy transfer based method to obtain distance changes due to agonist binding in the ligand binding domain in the presence of the transmembrane segments. These distance changes show that the cleft closure conformational change observed in the isolated ligand binding domain upon binding agonist is conserved in the receptor with the channel segments, thus establishing that the isolated ligand binding domain is a good model of the domain in the receptor containing the transmembrane segments.

Structural basis of the Ca2+ inhibitory mechanism of Drosophila Na+/Ca2+ exchanger CALX and its modification by alternative splicing.

The Na(+)/Ca(2+) exchanger CALX promotes Ca(2+) efflux in Drosophila sensory neuronal cells to facilitate light-mediated Ca(2+) homeostasis. CALX activity is negatively regulated by specific Ca(2+) interaction within its two intracellular Ca(2+) regulatory domains CBD1 and CBD2, yet how the Ca(2+) binding is converted to molecular motion to operate the exchanger is unknown. Here, we report crystal structures of the entire Ca(2+) regulatory domain CBD12 from two alternative splicing isoforms, CALX 1.1 and 1.2, exhibiting distinct regulatory Ca(2+) dependency. The structures show an open V-shaped conformation with four Ca(2+) ions bound on the CBD domain interface, confirmed by LRET analysis. The structures together with Ca(2+)-binding analysis support that the Ca(2+) inhibition of CALX is achieved by interdomain conformational changes induced by Ca(2+) binding at CBD1. The conformational difference between the two isoforms also indicates that alternative splicing adjusts the interdomain orientation angle to modify the Ca(2+) regulatory property of the exchangers.

Mental Health of Prisoners: Identifying Barriers to Mental Health Treatment and Medication Continuity

OBJECTIVES We assessed mental health screening and medication continuity in a nationally representative sample of US prisoners. METHODS We obtained data from 18 185 prisoners interviewed in the 2004 Survey of Inmates in State and Federal Correctional Facilities. We conducted survey logistic regressions with Stata version 13. RESULTS About 26% of the inmates were diagnosed with a mental health condition at some point during their lifetime, and a very small proportion (18%) were taking medication for their condition(s) on admission to prison. In prison, more than 50% of those who were medicated for mental health conditions at admission did not receive pharmacotherapy in prison. Inmates with schizophrenia were most likely to receive pharmacotherapy compared with those presenting with less overt conditions (e.g., depression). This lack of treatment continuity is partially attributable to screening procedures that do not result in treatment by a medical professional in prison. CONCLUSIONS A substantial portion of the prison population is not receiving treatment for mental health conditions. This treatment discontinuity has the potential to affect both recidivism and health care costs on release from prison.

A Quasi-Experimental Evaluation of the Effects of Police Body-Worn Cameras (BWCs) on Response-to-Resistance in a Large Metropolitan Police Department

ABSTRACT The current study provides a statistically rigorous program evaluation of the impact of police body-worn cameras (BWCs) on police response-to-resistance (e.g., use of force). Results indicate that BWC officers’ mean frequency of response-to-resistance decreased by 8.4% from the 12 months pre-BWC implementation to the 12 months post-BWC implementation compared with a 3.4% increase observed for the matched sample of non-BWC officers. Police departments should consider adopting BWCs alongside other strategies to reduce police response-to-resistance, and to improve transparency and accountability. Study limitations and directions for future research are also discussed.

Trends in Fighting and Violence Among Adolescents in the United States, 2002–2014

OBJECTIVES To examine trends in and correlates of fighting and violence among youths from the 3 largest racial/ethnic groups in the United States. METHODS We derived race/ethnicity-specific prevalence estimates for fighting, group fighting, and attacks with intent to harm from the National Survey on Drug Use and Health, a population-based study of youths aged 12 to 17 years. RESULTS The prevalence of youth fighting and violence decreased significantly in all racial/ethnic groups over the study period (2002-2014), dropping from a high of 33.6% in 2003 to a low of 23.7% in 2014, reflecting a 29% decrease in the relative proportion of young people involved in these behaviors. However, there was also a clear severity gradient in which year-by-year point estimates for fighting and violence were consistently highest among non-Hispanic African American youths, followed by Hispanic and then non-Hispanic White youths. CONCLUSIONS Although fighting and violence are on the decline among young people in general and across racial/ethnic subgroups, there is a stable pattern of disparities in youth involvement in these behaviors.

The Intersection of Perceptions and Experiences of Bullying by Race and Ethnicity among Middle School Students in the United States

Little is known about how ethnic identity influences bullying. Using a racially diverse sample, we examine how within-race perceptions match experiences. We utilize bivariate probit regression to examine the correlation between actual and perceived victimization and bullying experiences. Results suggest no differences in victimization by ethnicity but perceived victimization differed across groups. Perceived and actual bullying differed across all groups. School climate acted as a protective factor against bullying and victimization, but school diversity increased the likelihood of bullying by whites and Latinos. These findings shed light on the importance of ethnic identity in understanding the etiology of bullying.

Structural school safety measures, SROs, and school-related delinquent behavior and perceptions of safety: A state-of-the-art review

Purpose The purpose of this paper is to examine the impact of school safety measures, including SROs and safety personnel, on school-related delinquency and perceived safety. Design/methodology/approach Specifically, a comprehensive search of the literature was performed to identify studies published between January 1, 1998 and July 1, 2016 that focussed on structural school safety measures such as metal detectors, cameras, closed circuit television systems, and access control measures and/or school resource officers in primary and secondary schools. Only studies that relied on randomized controlled trials and pre-test/post-test designs evaluating the impact of at least one school safety measure in reference to a control condition were eligible for inclusion. Findings The results of this exhaustive search revealed 32 unique study samples that met the inclusion criteria. Results from the studies suggest that implementation of more security measures may not be an effective policy. More safety measures often result in a decline of student-perceived safety. Study limitations and directions for future research are also discussed. Originality/value Results from this meta-review can provide educational administrators, superintendents, and school safety policymakers with a synthesis of only the most rigorous and valid studies that evaluate the impact of school safety measures on both actual and perceived school-related delinquency and safety. This information will provide school safety decision makers with a state-of-the-art synthesis of how school safety measures impact school-related delinquency problems and safety, and which measures appear to be most effective for informing the allocation of scarce resources.