Colocalization of β-adrenergic receptors and caveolin within the plasma membrane

✍ Scribed by Carsten Schwencke; Satoshi Okumura; Manabu Yamamoto; Yong-Jian Geng; Yoshihiro Ishikawa

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 182 KB
• Volume: 75
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/(sici)1097-4644(19991001)75:1<64::aid-jcb7>3.0.co;2-l

✦ Synopsis

The rapid amplification of ␤-adrenergic receptor signaling involves the sequential activation of multiple signaling molecules ranging from the receptor to adenylyl cyclase. The prevailing view of the agonist-induced interaction between signaling molecules is based on random collisions between proteins that diffuse freely in the plasma membrane. The recent identification of G protein ␣and ␤␥-subunits in caveolae and their functional interaction with caveolin suggests that caveolae may participate in G protein-coupled signaling. We have investigated the potential interaction of ␤-adrenergic receptors with caveolin under resting conditions. ␤1and ␤2-adrenergic receptors were recombinantly overexpressed in COS-7 cells. Caveolae were isolated using the detergent-free sucrose gradient centrifugation method. ␤1and ␤2-adrenergic receptors were localized in the same gradient fractions as caveolin, where Gs␣-and ␤␥-subunits were detected as well. Immunofluorescence microscopy demonstrated the colocalization of ␤-adrenergic receptors with caveolin, indicating a nonrandom distribution of ␤-adrenergic receptors in the plasma membrane. Using polyhistidine-tagged recombinant proteins, ␤-adrenergic receptors were copurified with caveolin, suggesting that they were physically bound. Our results suggest that, in addition to clathrin-coated pits, caveolae may act as another plasma membrane microdomain to compartmentalize ␤-adrenergic receptors.