Interactions with PDZ Domain Proteins PIST/GOPC and PDZK1 Regulate Intracellular Sorting of the Somatostatin Receptor Subtype 5

Wolf Wente,Thomas Stroh,Alain Beaudet,Dietmar Richter,Hans-Jürgen Kreienkamp

doi:10.1074/jbc.m507198200

Abstract

By yeast two-hybrid screening we have identified interaction partners for the intracellular C-terminal tail of the human and rodent somatostatin receptor subtype 5 (SSTR5). Interactions with the PDZ domain-containing proteins PIST and PDZK1 are mediated by the PDZ ligand motif at the C terminus of the receptor; in case of the human and mouse (but not the rat) receptors, a slight sequence variation of this motif also allows for binding of the peroxisomal receptor PEX5. PIST is Golgi-associated and retains SSTR5 in the Golgi apparatus when coexpressed with the receptor; PDZK1 on the other hand associates with the SSTR5 at the plasma membrane. Endogenous SSTR5 in the neuroendocrine AtT-20 tumor cell line is colocalized with PIST in the Golgi apparatus. On a functional level, removal of the PDZ ligand motif of the receptor does not interfere with agonist-dependent internalization of the receptor or its targeting to a Golgi-associated compartment; however, recycling of the receptor to the plasma membrane after washout of the agonist is inhibited, suggesting that the PDZ-mediated interaction of SSTR5 is required for postendocytic sorting.

Highlights

Contain motifs for the interaction with PDZ domains
PDZ domain protein interacting with Tc10 (PIST, known as GOPC or CAL; Refs. 21–23), a PDZ domain protein that is widely expressed in the brain and periphery, was found to be a potential interaction partner of the human as well as the rat somatostatin receptor subtype 5 (SSTR5)
A deletion analysis demonstrated that the interaction between PIST and SSTR5 is mediated by the PDZ domain (TABLE ONE)

Summary

Introduction

PDZ domain proteins frequently act as scaffold molecules because of their multiple protein interaction motifs [6]. This type of interaction has the potential to target a receptor to specific subcellular domains and into specific signaling complexes. There are five SSTR subtypes in mammalian species, which form a rather homogeneous subfamily within the larger family of GPCRs, as they all preferentially couple to inhibitory, pertussis toxinsensitive G-proteins and exhibit common intracellular coupling patterns such as inhibition of adenylate cyclase [11] and activation of GIRK potassium channels [12]. Our data indicate that these proteins determine the intracellular sorting of the receptor; in particular, the PDZ-mediated interactions of SSTR5 appear to regulate targeting of the receptor from the Golgi/TGN to the plasma membrane

Methods

Results

Conclusion