A NOVEL EXPRESSION SYSTEM FOR G(S)-COUPLED RECEPTORS

Renal epithelial cells LLC-PK1 secrete high amounts of urokinase-type plasminogen activator (uPA) when stimulated through the cAMP-signaling pathway. Here we show that this characteristic can be used to identif y rapidly LLC-PK1-derived cell lines expressing heterologous receptors that couple to G(s)-proteins. A genomic clone encoding the mouse beta 2adrenergic receptor (beta2AR) was transfected stably into LLC-PK1 cel ls. Drug-resistant colonies were subsequently stimulated with isoprote renol and screened for the secretion uPA activity. Positive clones dis played dose-dependent uPA activity in response to isoproterenol, speci fically bound the beta2AR-agonist iodocyanopindolol and expressed beta 2AR-mRNA. The functional coupling of beta2AR expression to the inducib le uPA gene establishes that LLC-PK1 cells can be used to assay for be ta2AR (and beta2AR-agonist) function. Our data suggest that this syste m can be used for functional expression of other heterologous receptor s that couple to G(s)-proteins.