Expression and Localization of Adenylyl Cyclases and G Protein Receptors in Guinea Pig Ileum Caveolae and Lipid Rafts
In asthma, airway smooth muscle (ASM) becomes hyper-contractile, causing a restriction of airflow. β-adrenergic receptor (βAR) agonists activate adenylyl cyclase (AC) to increase cAMP production and relaxation of ASM. However, βAR appear to only couple to certain AC isoforms due to compartmentation in lipid rafts and caveolae. We examined the expression and localization of AC isoforms in primary mouse ASM. Enzymatic digestion of airway was followed by selection of single cells using a microscope and micropipette. We then prepared total RNA and analyzed AC expression via RT-PCR. Of the 9 AC isoforms, we found expression of AC6 and AC3, with lower levels of AC4. AC2 expression was only occasionally detected. We then examined the localization of both native and overexpressed ACÕs by confocal microscopy. After double staining with caveolin-1 antibody, we observed relatively high co-localization between AC3 (21.3%) or AC6 (20.2%) and caveolin-1. The degree of overlap was increased in cells overexpressing either AC isoform via incubation with recombinant adenoviruses (31.4% for AC3 and 29.7% for AC6). By contrast, low levels of co-localization were observed between AC2 and caveolin-1 (1.4%), with only a slight increase (9.6%) after infection with AC2 adenovirus. Our data indicate that mouse ASM express AC2, AC3, AC4 and AC6 but that only AC3 and AC6 are significantly co-localized with caveolin-1.
R Reece, X Liu, SQ Sun, FJ Ehlert and RS Ostrom. Expression and localization of adenylyl cyclases and G protein receptors in guinea pig ileum caveolae and lipid rafts. FASEB J, 21(6):A792, 2007.
Federation of American Society of Experimental Biology (FASEB)