homogenate was centrifuged at 2,000 G for 10 min. The supernatant was collected and centrifuged at 9,000 G for 20 min, and the
resultant supernatant was centrifuged at 180,000 G for 90 min. Essentially all β1AR and
β2AR were recovered in this final pellet. The pellet was reconstituted with RIPA buffer containing
protease inhibitor (Roche) then running buffer for Western blotting (anti-β1AR (Santa Cruz),
anti-β2AR (as above) and anti-Caveolin3 (BD Biosciences)).