A kinase-regulated PDZ-domain interaction controls endocytic sorting of the β2-adrenergic receptor

Abstract

A fundamental question in cell biology is how membrane proteins are sorted in the endocytic pathway. The sorting of internalized beta2-adrenergic receptors between recycling endosomes and lysosomes is responsible for opposite effects on signal transduction and is regulated by physiological stimuli. Here we describe a mechanism that controls this sorting operation, which is mediated by a family of conserved protein-interaction modules called PDZ domains. The phosphoprotein EBP50 (for ezrinradixin-moesin(ERM)-binding phosphoprotein-50) binds to the cytoplasmic tail of the beta2-adrenergic receptor through a PDZ domain and to the cortical actin cytoskeleton through an ERM-binding domain. Disrupting the interaction of EBP50 with either domain or depolymerization of the actin cytoskeleton itself causes missorting of endocytosed beta2-adrenergic receptors but does not affect the recycling of transferrin receptors. A serine residue at position 411 in the tail of the beta2-adrenergic receptor is a substrate for phosphorylation by GRK-5 (for G-protein-coupled-receptor kinase-5) and is required for interaction with EBP50 and for proper recycling of the receptor. Our results identify a new role for PDZ-domain-mediated protein interactions and for the actin cytoskeleton in endocytic sorting, and suggest a mechanism by which GRK-mediated phosphorylation could regulate membrane trafficking of G-protein-coupled receptors after endocytosis.

CART: An Hrs/Actinin-4/BERP/Myosin V Protein Complex Required for Efficient Receptor Recycling

“…Recent results have suggested a role for myosins in recycling (Neuhaus and Soldati, 2000;Lapierre et al, 2001), implying a role for the actin cytoskeleton in this process. Studies using drugs that depolymerize actin filaments also implicate actin at a recycling step (Durrbach et al, 1996;Cao et al, 1999;Zaslaver et al, 2001;Sheff et al, 2002;Engqvist-Goldstein and Drubin, 2003). We have found that an endosome-associated protein, hrs, is part of a protein complex that includes actinin-4, BERP, and myosin Vb, designated CART.…”

Sex-specific association between bipolar affective disorder in women and GPR50, an X-linked orphan G protein-coupled receptor

“…A mutation in the distal portion of the b2-adrenergic receptor has been shown to disrupt a PDZ domainmediated interaction, resulting in reduced receptor recycling and increased targeting to lysosomes. 28 The clear association with female subjects affected with major mental illness and not with male subjects is intriguing. There is no reported gender bias in the numbers of individuals affected by BPAD.…”

The Lymphocyte Receptor CD6 Interacts with Syntenin-1, a Scaffolding Protein Containing PDZ Domains

“…PDZ domains are widespread among signaling and cytoskeletal proteins and are thought to function as molecular scaffolds for the assembly of multiprotein complexes and to localize them to specialized membrane and subcellular compartments (50). Thus, PDZ proteins are pivotal for the correct organization of protein complexes in cell-cell junctions (51), in phototransduction cascades (52), in neuronal synapses (53), and for sorting/targeting proteins to specific subcellular sites (54,55). PDZ domains generally recognize short sequence motifs present at the last four to five C-terminal residues on their target proteins and are typically grouped into three different classes: class I PDZ domains recognize the motif -X-(S/T)-X-, class II PDZ domains the motif -X--X-, and class III PDZ domains the motif D/E-X-( represents a bulky hydrophobic amino acid, and X any amino acid) (49).…”