Dimerization Rules of Mammalian PAS Proteins.

The PAS (PER, ARNT, SIM) protein family plays a vital role in mammalian biology and human disease. This analysis arose from an interest in the signaling mechanics by the Ah receptor (AHR) and the Ah receptor nuclear translocator (ARNT). After more than fifty years by studying this and related mammalian sensor systems, describing the role of PAS domains in signal transduction is still challenging. In this perspective, we attempt to interpret recent studies of mammalian PAS protein structure and consider how this new insight might explain how these domains are employed in human signal transduction with an eye towards developing strategies to target and engineer these molecules for a new generation of therapeutics. Our approach is to integrate our understanding of PAS protein history, cell biology, and molecular biology with recent structural discoveries to help explain the mechanics of mammalian PAS protein signaling. As a learning set, we focus on sequences and crystal structures of mammalian PAS protein dimers that can be visualized using readily available software.

Enhanced sensitivity of an Ah-receptor system in yeast through condition modification and use of mammalian modifiers.

Proteins, such as the Ah receptor (AHR), hold potential as sensors to detect ligands in environmental and biological samples, and may also serve as tools to regulate biosynthetic and industrial processes. The AHR is also a prototype system for the PAS superfamily that can sense and mediate adaptation to signals as diverse as light, voltage, oxygen and an array of small molecules. The yeast, S. cerevisiae, has proven to be an important model to study the signal transduction of sensors like the AHR because of its ease of use, numerous available strategies for genetic manipulation, and capacity for heterologous expression. To better understand the utility of sensor proteins as components of yeast detection systems, we characterized a chimeric AHR-LexA system that drives expression from a Lex operator (LexO) driven, beta-galactosidase (ß-Gal) reporter. In this report, we demonstrate that improvements in assays sensitivity and pharmacology can arise from the careful optimization of yeast growth phase and the duration of ligand exposure. We also report that the coexpression of heterotypic modifiers from mammalian cells (e.g., the ARA9 and ARA3 proteins), can improve yeast assay performance. We propose that complementing these assay improvements with previously reported yeast mutations described by others will expand the utility of the AHR for biotechnology applications.

The aryl hydrocarbon receptor as a model PAS sensor.

Proteins containing PER-ARNT-SIM (PAS) domains are commonly associated with environmental adaptation in a variety of organisms. The PAS domain is found in proteins throughout Archaea, Bacteria, and Eukarya and often binds small-molecules, supports protein-protein interactions, and transduces input signals to mediate an adaptive physiological response. Signaling events mediated by PAS sensors can occur through induced phosphorelays or genomic events that are often dependent upon PAS domain interactions. In this perspective, we briefly discuss the diversity of PAS domain containing proteins, with particular emphasis on the prototype member, the aryl hydrocarbon receptor (AHR). This ligand-activated transcription factor acts as a sensor of the chemical environment in humans and many chordates. We conclude with the idea that since mammalian PAS proteins often act through PAS-PAS dimers, undocumented interactions of this type may link biological processes that we currently think of as independent. To support this idea, we present a framework to guide future experiments aimed at fully elucidating the spectrum of PAS-PAS interactions with an eye towards understanding how they might influence environmental sensing in human and wildlife populations.

Generation of an Allelic Series at the Ahr Locus Using an Edited Recombinant Approach.

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor and a member of the PER-ARNT-SIM (PAS) superfamily of environmental sensors. The AHR is involved in a series of biological processes including adaptive metabolism of xenobiotics, toxicity of certain environmental pollutants, vascular development, fertility, and immune function. Mouse models, including the Ahr null and Ahr conditional null (Ahrfx) mice, are widely used for the study of AHR-mediated biology and toxicity. The Ahr conditional null mouse harbors the low-affinity Ahrd allele that exhibits approximately a 10-fold lower binding affinity for certain xenobiotic AHR ligands than the widely used C57BL/6 mouse that harbors the higher affinity Ahrb1 allele. Here, we report a novel mouse model that introduces a V375A polymorphism that converts the low-affinity allele into a high-affinity allele, offering a more sensitive conditional model. In the generation of this novel conditional allele, two additional mutants arose, including a 3-bp deletion in the PAS-B domain (AhrNG367R) and an early termination codon in the PAS-B domain (AhrTer383). The AhrNG367R allele presents as a phenocopy of the null and the AhrTer383 allele presents as an antimorph when assessing for the ductus venosus and liver lobe weight endpoints. These new models represent a series of tools that will be useful in further characterizing AHR biology.

Signs of Severity (SOS) ED Escalation Guide: Bridging the Experience Gap.

INTRODUCTION: This study evaluated the introduction of an ED Escalation Guide (EDEG) as an early warning system for the many new graduate nurses in the emergency department. The EDEG is a chart that provides ED-appropriate parameters to prioritize both vital signs and critical symptoms. Scenario quizzes were used to evaluate its usefulness. METHODS: Comparative quizzes that required prioritizing the urgency of patient symptoms were given to emergency nurses with varying levels of experience, with and without the use of the EDEG. The quizzes, with scenarios adapted from the Emergency Severity Index (ESI) Handbook, were given to ED RNs 1 week apart; the second quiz included availability of the EDEG. Scores were compared based on demographic data that included years of ED experience and clinical expertise. RESULTS: RNs with less than 1 year of ED experience showed a 29% improvement in scenario scores with use of the EDEG. Those with more experience had similar scores with and without the availability of the guide, but increasing experience led to higher scores. A log kept by new emergency nurses using the EDEG showed accuracy and greater confidence in notifying ED physicians. DISCUSSION: RNs with less than 1 year of ED experience might not recognize or report critical symptoms without a guide. The EDEG helps new emergency nurses to prioritize the urgency of clinical symptoms better and gives them the confidence to report these clinical symptoms. Early warning systems, such as the EDEG, can be valuable tools for inexperienced emergency nurses.

Emergency Nurse Transport of Telemetry Patients: Benefits and Drawbacks.

PROBLEM: Emergency nurse-accompanied telemetry transport on admission to the hospital is a common practice. Potential drawbacks include inefficient use of nursing resources, unnecessary telemetry transports, and disruption of care for remaining ED patients. METHODS: This was a 2-part descriptive quality improvement study using retrospective chart review and prospective documentation of patient transports. Charts were selected by American Heart Association Practice Standards for ECG Monitoring to classify transported telemetry patients into 3 categories. Patient characteristics and adverse events were assessed. Prospectively, the length of transport time and the number and severity of patients the transport nurse left in the emergency department were also recorded. RESULTS: Zero adverse events occurred during any transport. Transport time ranged from 5 to 38 minutes, with a mean of 16.5 minutes. The normal patient ratio increased for nursing staff remaining in the emergency department for the period of the transport, with 74% of patients left in the emergency department classified into high-risk Emergency Severity Index categories 1 and 2. IMPLICATIONS FOR PRACTICE: Findings provided evidence that low-risk telemetry patients had minimal chance of adverse events during transport and highlighted added risks for the remaining emergency patients. Alternative models and interventions are needed to identify appropriate patients for telemetry transport, assign appropriate staff such as licensed paramedics for transport, and evaluate alternative models of nursing care and teamwork in the emergency department.