Reticulon1-C modulates protein disulphide isomerase function

P Bernardoni,C Montagna,B Fazi,G Filomeni,M R Ciriolo,R Nardacci,M Piacentini,A Costanzi,F Di Sano

doi:10.1038/cddis.2013.113

Abstract

Endoplasmic reticulum (ER) is the primary site for the synthesis and folding of secreted and membrane-bound proteins. Accumulation of unfolded and misfolded proteins in ER underlies a wide range of human neurodegenerative disorders. Hence, molecules regulating the ER stress response represent potential candidates as drug targets for tackling these diseases. Protein disulphide isomerase (PDI) is a chaperone involved in ER stress pathway, its activity being an important cellular defense against protein misfolding. Here, we demonstrate that human neuroblastoma SH-SY5Y cells overexpressing the reticulon protein 1-C (RTN1-C) reticulon family member show a PDI punctuate subcellular distribution identified as ER vesicles. This represents an event associated with a significant increase of PDI enzymatic activity. We provide evidence that the modulation of PDI localization and activity does not only rely upon ER stress induction or upregulation of its synthesis, but tightly correlates to an alteration in its nitrosylation status. By using different RTN1-C mutants, we demonstrate that the observed effects depend on RTN1-C N-terminal region and on the integrity of the microtubule network. Overall, our results indicate that RTN1-C induces PDI redistribution in ER vesicles, and concomitantly modulates its activity by decreasing the levels of its S-nitrosylated form. Thus RTN1-C represents a promising candidate to modulate PDI function.

Highlights

In recent years, Protein disulfide isomerases (PDIs) have been identified as novel therapeutic targets for the unfolded protein response (UPR) modulation
We found that overexpression of reticulon protein 1-C (RTN1-C) induced a marked change in PDI distribution from a diffuse to a more punctate pattern (Figure 1a)
We have investigated the biological effects of RTN1-C, a member of the RTN family proteins, on PDI, in cells from neuronal origin

Summary

Introduction

PDIs have been identified as novel therapeutic targets for the unfolded protein response (UPR) modulation. An increase of PDI activity could counteract protein inclusions formation, which are distinctive signs of neurodegenerative diseases.[3,4] Consistent with this assumption, several reports suggest that PDI function has a crucial role in neuronal cell death, as it is able to attenuate neurotoxicity associated with the accumulation of aggregated proteins which is, in turn, responsible for neurodegenerative processes. It has been demonstrated that RTNs interact with several proteins regulating endo- and exocytosis processes.[9,10] More recent studies have involved RTNs in several CNS disorders,[11,12,13] such as AD and ALS.[8] Considering this context we decided here to investigate the role of reticulon protein 1-C (RTN1-C) on the intracellular localization and functional modulation of PDI. We identified the N-terminal domain of the RTN1-C as the putative domain involved in the modulation of these events

Methods

Results

Conclusion