The C-terminal domain of zDHHC2 contains distinct sorting signals that regulate intracellular localisation in neurons and neuroendocrine cells.

Christine Salaun,Luke H Chamberlain,Louise Ritchie,Trevor J Bushell,Jennifer Greaves

doi:10.1016/j.mcn.2017.07.007

Christine Salaun, Luke H Chamberlain + Show 3 more

Open Access

https://doi.org/10.1016/j.mcn.2017.07.007

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Abstract

The S-acyltransferase zDHHC2 mediates dynamic S-acylation of PSD95 and AKAP79/150, which impacts synaptic targeting of AMPA receptors. zDHHC2 is responsive to synaptic activity and catalyses the increased S-acylation of PSD95 that occurs following action potential blockade or application of ionotropic glutamate receptor antagonists. These treatments have been proposed to increase plasma membrane delivery of zDHHC2 via an endosomal cycling pathway, enhancing substrate accessibility. To generate an improved understanding of zDHHC2 trafficking and how this might be regulated by neuronal activity, we searched for intramolecular signals that regulate enzyme localisation. Two signals were mapped to the C-terminal tail of zDHHC2: a non-canonical dileucine motif [SxxxLL] and a downstream NP motif. Mutation of these signals enhanced plasma membrane accumulation of zDHHC2 in both neuroendocrine PC12 cells and rat hippocampal neurons, consistent with reduced endocytic retrieval. Furthermore, mutation of these signals also increased accumulation of the enzyme in neurites. Interestingly, several threonine and serine residues are adjacent to these sorting motifs and analysis of phospho-mimetic mutants highlighted a potential role for phosphorylation in regulating the efficacy of these signals. This study offers new molecular insight into the signals that determine zDHHC2 localisation and highlights a potential mechanism to regulate these trafficking signals.

Highlights

S-acylation is a reversible post-translational modification involving the attachment of fatty acids onto cysteine residues (Salaun et al, 2010), which regulates the stability, localisation and function of a broad array of different proteins (Salaun et al, 2010; Linder and Deschenes, 2007; Chamberlain and Shipston, 2015)
Our previous study showed that zDHHC2 cycles between the plasma membrane and recycling endosomes and that sorting signals regulating this dynamic localisation are located in the C-terminal tail of the enzyme (Greaves et al, 2011)
We have previously shown that zDHHC2 cycles between the plasma membrane and endosomes, and that this was regulated by C-terminal sequences (Greaves et al, 2011)

Summary

Introduction

S-acylation (or palmitoylation) is a reversible post-translational modification involving the attachment of fatty acids onto cysteine residues (Salaun et al, 2010), which regulates the stability, localisation and function of a broad array of different proteins (Salaun et al, 2010; Linder and Deschenes, 2007; Chamberlain and Shipston, 2015). Recent studies have uncovered an intriguing role for S-acylation in the regulation of neuronal physiology (Fukata and Fukata, 2010) This modification has been suggested to play an important role in the regulation of neurotransmitter receptors, including the γsubunit of GABA(A) receptors (Keller et al, 2004), and AMPA and NMDA glutamate receptor (AMPAR and NMDAR) subunits (Hayashi et al, 2005; Hayashi et al, 2009). In addition to direct modification of AMPAR subunits, the synaptic targeting of these receptors is thought to be regulated by the S-acylation of a number of other accessory proteins, including GRIP1b (Thomas et al, 2012), AKAP79/150 (Woolfrey et al, 2015) and PSD95 (El-Husseini, 2002). S-acylation of PSD95 is important for targeting of this molecular scaffold to post-synaptic regions, where it regulates synaptic clustering of AMPAR (Craven et al, 1999), indirectly via interaction with the Stargazin protein (Chen et al, 2000)

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