Sorting of β1-Adrenergic Receptors Is Mediated by Pathways That Are Either Dependent on or Independent of Type I PDZ, Protein Kinase A (PKA), and SAP97

The (1)-adrenergic receptor ((1)-AR) is a target for treatment of major cardiovascular diseases, such as heart failure and hypertension. Recycling of agonist-internalized (1)-AR is dependent on type I PSD-95/DLG/ZO1 (PDZ) in the C-tail of the (1)-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 (1)-AR and its binding to the PDZ-binding protein SAP97. These studies indicated that (1)-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 (1)-AR. (1)-AR chimera containing the type I PDZ of the (2)-adrenergic receptor that does not bind to SAP97 failed to recycle except when serine 312 was mutated to aspartic acid. (1)-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 (1)-AR chimera derived from -opioid, dopamine 1, or GluR2 receptors promoted rapid recycling of chimeric (1)-AR in a SAP97- and PKA-independent manner. Moreover, the nature of the residue at position -3 in the PDZ regulated whether the (1)-AR was internalized alone or in complex with SAP97. These results indicate that divergent pathways were involved in trafficking the (1)-AR and provide a roadmap for its trafficking via type I PDZs versus non-PDZs.