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Epitope‐tagged knockin mice reveal ligand‐selective internalization that explains differential desensitization of alpha2‐adrenergic responses in native sympathetic neurons
Author(s) -
Lu Roujian,
Zhang Youwen,
Li Yong,
Jiao Kai,
Zhou Yi,
Limbird Lee,
Wang Qin
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.725.10
Subject(s) - guanfacine , homologous desensitization , clonidine , endocytosis , receptor , adrenergic receptor , biology , g protein coupled receptor , desensitization (medicine) , microbiology and biotechnology , pharmacology , chemistry , endocrinology , biochemistry
Using a gene targeting approach, we previously generated a knock‐in mouse line, in which N‐terminal hemagglutinin (HA) epitope‐tagged α 2A adrenergic receptor (AR) expression was driven by the endogenous mouse α 2A AR locus. This line made it possible, for the first time, to evaluate α 2A AR endocytosis and α 2A AR‐mediated inhibition of Ca 2+ currents in native neurons in response to clonidine and guanfacine, two drugs commonly used in treating attention deficit and hyperactivity disorder (ADHD) and eliciting analgesia through actions on the α 2A AR. Exploiting this line, we found that the accelerated desensitization to clonidine compared to suppression of Ca 2+ currents by guanfacine paralleled a more marked receptor phosphorylation and endocytosis of α 2A AR than guanfacine. Interestingly, however, both guanfacine and clonidine share the same efficacy in coupling receptor occupancy to activation of G proteins, based on findings from receptor binding and α 2A AR‐ activation of GTPγS studies. Our data provide strong evidence showing functional relevance of differential regulation of GPCR endocytosis by different ligands on receptor‐mediated signaling in native cells, and may represent an important determinant of therapeutic strategies, i.e. desensitizing or non‐desensitizing signals, depending on the pathophysiology being targeted.