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标题：Targeted transgenesis reveals discrete attenuator functions of GRK and PKA in airway β2-adrenergic receptor physiologic signaling
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作者：Wayne C. H. Wang ; Kathryn A. Mihlbachler ; Alicyn C. Brunnett 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：35
页码：15007-15012
DOI：10.1073/pnas.0906034106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Phosphorylation by protein kinase A (PKA) and G protein-coupled receptor kinases (GRKs) desensitize {beta}2-adrenergic receptor ({beta}2AR) signaling, and these are thought to be mechanisms involved with cell and organ homeostasis and tolerance to agonists. However, there is little direct evidence that these events are relevant to {beta}2AR physiological function, such as airway smooth muscle (ASM) relaxation leading to bronchodilation. To maintain cell- and receptor-specificity without altering the natural complement of kinases/arrestins, transgenic mice were generated expressing the human WT and mutated {beta}2ARs lacking PKA and/or GRK phosphorylation sites on ASM at {approx}4-fold over background. Functional gains in response to {beta}-agonist from the selective loss of these mechanisms were determined in mouse airways. Relaxation kinetics were altered in all mutant airways compared with {beta}2WT. At low receptor occupancy, {beta}2PKA(-) had enhanced agonist-promoted relaxation, while {beta}2GRK(-) airways were unaffected. In contrast, at saturating agonist concentrations, the greatest relaxation enhancement was with {beta}2GRK(-), with no evidence for additivity when PKA sites were also removed. For the full range of responses, the {beta}2PKA(-)/GRK(-) airways had the greatest relaxation efficiency, indicating a graded effect of GRKs as agonist concentration increased. ASM cAMP levels paralleled relaxation phenotypes. No interaction between PKA phosphorylation of {beta}2AR and GRK-promoted events was identified by {beta}-arrestin-2 recruitment. Thus, these two mechanisms indeed impact a relevant {beta}2AR physiologic function, acting as attenuators of the acute response, and represent specific interfaces where adjunct therapy or biased ligands may improve {beta}-agonist treatment of obstructive lung disease.
关键词：desensitization ; adenylyl cyclase ; smooth muscle ; asthma