A Novel Sorting Sequence in the β2-Adrenergic Receptor Switches Recycling from Default to the Hrs-dependent Mechanism

Aylin C Hanyaloglu,Mark Von Zastrow

doi:10.1074/jbc.m605398200

Aylin C Hanyaloglu, Mark Von Zastrow

Open Access

https://doi.org/10.1074/jbc.m605398200

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Abstract

Plasma membrane recycling of G protein-coupled receptors can occur by at least two distinct mechanisms as follows: a "default" mechanism that occurs nonselectively, and a specifically sorted mechanism that requires the endosome-associated protein Hrs. In this study we have defined a sequence in the beta2-adrenergic receptor cytoplasmic tail that confers Hrs dependence on receptor recycling. This sequence resembles acidic dileucine class motifs found in other membrane proteins but is structurally and functionally distinct from previously identified sorting sequences. Mutation of the novel sorting sequence rendered plasma membrane recycling independent of Hrs and independent of a distal PDZ ligand required for Hrs-dependent recycling. We propose that the novel sorting sequence functions to "switch" endocytic trafficking between mechanistically distinct recycling modes, thereby explaining failure of the wild type beta2-adrenergic receptor to recycle efficiently by default.

Highlights

There is increasing evidence that a number of G protein-coupled receptors (GPCRs) require specific structural determinant(s) within their cytoplasmic domains in order to undergo efficient recycling to the plasma
The C-terminal PDZ Ligand Present in the ␤2ADR Cytoplasmic Tail Is Not Fully Sufficient to Confer hepatocyte-growth factor receptor substrate (Hrs)-dependent Recycling on a Chimeric Mutant Vasopressin Receptor—Previous studies defined a minimal recycling signal, contained within the distal 4 –10 residues of the ␤2ADR C-terminal tail (C-tail), which is necessary for efficient recycling of the ␤2ADR and sufficient to re-route a distinct GPCR from lysosomal to recycling pathways [5,6,7, 15]
We recently showed that a sequence corresponding to residues 366 – 413 of the ␤2ADR C-tail, which includes these distal residues, is sufficient to confer Hrs-dependent recycling when fused to a truncated mutant V2 vasopressin receptor (V2R 362T) that otherwise recycles by default and in an Hrs-independent manner [16, 20, 24]

Summary

Introduction

There is increasing evidence that a number of GPCRs require specific structural determinant(s) within their cytoplasmic domains in order to undergo efficient recycling to the plasma. We analyzed endocytic trafficking of the V2R 362/ ␤2ADR C-tail chimeras containing a single C-terminal alanine addition, which disrupts the distal PDZ ligand required for recycling of wild type receptors [5, 7] when combined with the AKANKAA mutation of the acidic dileucine sequence.

Results

Conclusion