ABSTRACT
The ß1-adrenergic receptor (ß1-AR) is a target for treatment of major cardiovascular diseases, such as heart failure and hypertension. Recycling of agonist-internalized ß1-AR is dependent on type I PSD-95/DLG/ZO1 (PDZ) in the C-tail of the ß1-AR and on protein kinase A (PKA) activity (Gardner, L. A., Naren, A. P., and Bahouth, S. W. (2007) J. Biol. Chem. 282, 5085-5099). We explored the effects of point mutations in the PDZ and in the activity of PKA on recycling of the ß1-AR and its binding to the PDZ-binding protein SAP97. These studies indicated that ß1-AR recycling was inhibited by PKA inhibitors and by mutations in the PDZ that interfered with SAP97 binding. The trafficking effects of short sequences differing in PDZ and SAP97 binding were examined using chimeric mutant ß1-AR. ß1-AR chimera containing the type I PDZ of the ß2-adrenergic receptor that does not bind to SAP97 failed to recycle except when serine 312 was mutated to aspartic acid. ß1-AR chimera with type I PDZ sequences from the C-tails of aquaporin-2 or GluR1 recycled in a SAP97- and PKA-dependent manner. Non-PDZ ß1-AR chimera derived from µ-opioid, dopamine 1, or GluR2 receptors promoted rapid recycling of chimeric ß1-AR in a SAP97- and PKA-independent manner. Moreover, the nature of the residue at position -3 in the PDZ regulated whether the ß1-AR was internalized alone or in complex with SAP97. These results indicate that divergent pathways were involved in trafficking the ß1-AR and provide a roadmap for its trafficking via type I PDZs versus non-PDZs.
