Our goal is to identify molecular mechanisms involved in the regulation of the beta-adrenergic receptor (BAR)-coupled adenylyl cyclase. Although there are three subtypes, B1AR, B2AR and B3AR, the physiological relevance of each remains to be elucidated. One possibility is that they may be regulated differently by agonists and other modulators. At least three major mechanisms of receptor regulation have been identified: desensitization, internalization, and down-regulation. We and others have shown that for the human subtypes, the ability to undergo regulation is B2AR