Many major signaling events in the lung are carried out by the superfamily of G-protein coupled receptors (GPCRs). These include bronchial smooth muscle relaxation and contraction, mucous secretion, ciliary beat frequency, inflammation, immune cell trafficking, pulmonary vascular tone and permeability, and alveolar fluid and electrolyte transport, as well as many yet to be defined functions. Approximately 75 GPCRs are estimated to be expressed in human lung. Within the next five years, the great majority of all therapeutic agents will target GPCRs. However, the physiologic, pathologic, and pharmacologic behavior of GPCR signaling displays substantial interindividual variability which is thought to be due to common variants (polymorphisms) of the genes encoding these receptors. Such polymorphisms have been estimated to account for as much as 50% of the variability in the response to therapeutic agonists and antagonists targeted to GPCRs. Indeed, with just one GPCR, the (2-adrenergic receptor, we have shown that coding and promoter polymorphisms alter receptor expression, function, and regulation in vitro in cells, and in asthmatic patients, they are associated with clinical phenotypes and the response to beta-agonist therapy. The long-term goals of this proposal are to identify polymorphisms of up to 20 pulmonary GPCR genes, and by the use of recombinant expression techniques to delineate their biochemical and pharmacologic impact on cellular signaling relevant to lung homeostasis and pathobiology.
In Aim 1, the polymorphisms of these 20 GPCR genes will be delineated in the promoter, 5' untranslated, coding, intron/exon junctions, and 3' untranslated regions from genomic DNA samples from a cohort of 60 ethnically diverse individuals.
In Aim 2, the common combinations of polymorphisms (haplotypes) will be delineated in the population.
In Aim 3, constructs will be developed and model cell systems utilized for recombinant expression of GPCR haplotypes to determine the biological effects of polymorphisms on receptor expression, signaling, or regulation. These studies will provide the basis for interindividual susceptibility and therapeutic responsiveness, the variability in pathobiology, and the potential for developing new treatment strategies, for a diverse range of lung diseases including asthma, pulmonary hypertension, pneumonia, pulmonary fibrosis, COPD, and pulmonary edema.
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