N-Ethylmaleimide-Sensitive Factor Regulates β₂ Adrenoceptor Trafficking and Signaling in Cardiomyocytes

Engineered Protein Connectivity to Actin Mimics PDZ-dependent Recycling of G Protein-coupled Receptors but Not Its Regulation by Hrs

“…Thus, while the present results argue strongly that ERM-actin linkage is a sufficient basis for a core mechanism of sequence-depend- ent recycling, it is likely that additional regulation of recycling occurs physiologically at the level of the PDZ protein itself. It will be interesting in future studies to investigate the potential role of various PDZ proteins and non-ERM protein interactions with NHERF/EBP50 family members (22,23,25) in regulating, and perhaps conferring additional specificity on, PDZ-dependent recycling that occurs in a native cellular context (20,43).…”

“…We note, for example, that hScrib/ ßPIX/GIT1-dependent recycling of thyrotropin receptors is regulated by theGTPaseArf6andAKAP79/SAP97-dependent recycling of ␤1-adrenergic receptors involves PKA-mediated phosphorylation of the receptor (30,31). Thus, if actin connectivity contributes to recycling via these alternative PDZ-linked protein complexes, it is likely that there exists additional cellular regulation dependent on the proximal PDZ domain-mediated interaction with the receptor that occursnaturally.Also,giventhatPDZdependent recycling of GPCRs occurs in diverse cell types, including neurons (43) and cardiac muscle cells (20), the possibility that distinct PDZlinked complexes also confer cell type-specific regulation merits future study. It is also interesting to note that efficient recycling of the ␣1b-adrenergic receptor, although not directed by a PDZ-mediated protein interaction, is actin-dependent and requires an ERM protein binding domain present in the receptor (33).…”

“…The ␤2AR-derived recycling sequence conforms to a canonical PDZ (PSD-95/Discs Large/ZO-1) protein-binding determinant (henceforth called PDZbd), and PDZ-mediated protein association(s) with this sequence appear to be primarily responsible for its endocytic sorting activity (17)(18)(19)(20). Fusion of this sequence to the cytoplasmic tail of the ␦OR effectively re-routes endocytic trafficking of engineered receptors from lysosomal to recycling pathways, establishing the sufficiency of the PDZbd to function as a transplantable sorting determinant (18).…”

Protein Interacting with C Kinase 1 (PICK1) Reduces Reinsertion Rates of Interaction Partners Sorted to Rab11-dependent Slow Recycling Pathway

“…␤ 2 AR, ␤ 2 DAT8, and ␤ 2 DAT8 ϩAla showed similar surface expression, and induction of eYFP-PICK1 expression (ϩTet) did not affect their basal surface expression (data not shown). Because binding of NSF (59,60) and the PDZ domain protein NHERF1 (Na ϩ /H ϩ exchanger regulatory factor 1) (61, 62) to the extreme ␤ 2 AR C terminus was suggested previously to regulate recycling of the ␤ 2 AR, we first compared the trafficking of the fusion proteins ␤ 2 DAT8 and ␤ 2 DAT8 ϩAla with ␤ 2 AR. Just like ␤ 2 AR itself, the fusion proteins were internalized robustly in response to 10 M Iso (25 min 10 M), and notably, this was not affected by induction of eYFP-PICK1 expression (ϩTet); i.e.…”

Regulation of G protein-coupled receptor trafficking and signaling by Rab GTPases

“…3 However, receptor trafficking can be much more complex, as β 2 AR recycling has also been shown to actually switch the receptor's traditional coupling with Gα s to Gα i , and the AT1R compartmentalizes extracellular regulated kinase (ERK1/2) complexes to endosomes. 1,4 endosomal compartment. 21 Although dephosphorylation of cAMP-dependent protein kinase phosphorylated β 2 AR does not require endocytosis, 22 it remains unknown whether the dephosphorylation of PKC phosphorylated mGluR1a either occurs at the cell surface or requires endocytosis to endosomes.…”