Project Summary Our renewal of this interdisciplinary PPG remains focused on the theme of novel molecular mechanisms to inhibit human airway smooth muscle (HASM) contraction and promote bronchodilation within the context of airway inflammation and asthma. The principal hypothesis states that G protein coupled receptor (GPCR) desensitization and unbiased signaling limits the efficacy of conventional bronchodilators, such that targeting desensitization mechanisms, promoting biased agonism, circumventing mechanisms of ASM hypercontractility/airway hyperresponsiveness (AHR), or engaging novel bronchorelaxant mechanisms in HASM will provide superior therapy for asthma. Each Project addresses this hypothesis by either: 1) optimizing pro- relaxant signaling abilities of one of 3 different GPCRs using strategies rooted in cutting edge biophysical or pharmacological approaches; or 2) establishing novel intracellular targets mediating inflammation-driven AHR and increased GPCR pro-contractile signaling. Project 1 will establish the mechanisms by which TGF-β1 modulates excitation-contraction (EC) coupling of HASM and thereby identify novel therapeutic targets linked to both AHR and increased GPCR-mediated contraction. Project 2 will advance the recent discovery of bitter taste receptors (TAS2R) as novel bronchodilators clarifying the role of TAS2R subtypes in HASM, their mode of regulation and means to improve their efficacy through biased agonism. Project 3 will characterize the molecular basis of β2AR biased signaling to develop compounds that mediate Gs-biased signaling through either inhibition of β-arrestin interaction with the agonist-occupied β2AR (arrestin-biased negative allosteric modulators (NAMs)) or by enhancing coupling of the β2AR to Gs (biased orthosteric agonists). Project 4 will similarly characterize the mechanisms underlying biased signaling of OGR1, develop new biased OGR1 benzodiazepine derivatives with superior ability to bronchodilate, and determine the relative contribution of and mechanisms underlying peripheral benzodiazepine receptor activation by candidate drugs. The four projects will be supported by Core A that will use high through-put screening of small molecule libraries, whole genome, pooled shRNA libraries and virtual screening approaches to identify targets and effectors of bronchodilation. Core B will provide all de-identified human cell and tissue models to study novel mechanisms regulating EC coupling in HASM. Core C will provide administrative support for the program. The strengths of this Program are the common focus on a single theme and the productive working relationship among investigators with the ability to apply cutting edge GPCR biology to key questions in asthma biology and pharmacology.