CHIP, a carboxy terminus HSP-70 interacting protein, prevents cell death induced by endoplasmic reticulum stress in the central nervous system.

Felipe Cabral Miranda,Rafael Linden,Hilda Petrs-Silva,William W Hauswirth,Juliana Adã£O-Novaes,Luciana B Chiarini

doi:10.3389/fncel.2014.00438

Abstract

Endoplasmic reticulum (ER) stress and protein misfolding are associated with various neurodegenerative diseases. ER stress activates unfolded protein response (UPR), an adaptative response. However, severe ER stress can induce cell death. Here we show that the E3 ubiquitin ligase and co-chaperone Carboxyl Terminus HSP70/90 Interacting Protein (CHIP) prevents neuron death in the hippocampus induced by severe ER stress. Organotypic hippocampal slice cultures (OHSCs) were exposed to Tunicamycin, a pharmacological ER stress inducer, to trigger cell death. Overexpression of CHIP was achieved with a recombinant adeno-associated viral vector (rAAV) and significantly diminished ER stress-induced cell death, as shown by analysis of propidium iodide (PI) uptake, condensed chromatin, TUNEL and cleaved caspase 3 in the CA1 region of OHSCs. In addition, overexpression of CHIP prevented upregulation of both CHOP and p53 both pro-apoptotic pathways induced by ER stress. We also detected an attenuation of eIF2a phosphorylation promoted by ER stress. However, CHIP did not prevent upregulation of BiP/GRP78 induced by UPR. These data indicate that overexpression of CHIP attenuates ER-stress death response while maintain ER stress adaptative response in the central nervous system. These results indicate a neuroprotective role for CHIP upon UPR signaling. CHIP emerge as a candidate for clinical intervention in neurodegenerative diseases associated with ER stress.

Highlights

Cells present ingenious mechanisms of protein quality control to avoid aggregation of unfolded proteins and to guarantee correct conformation of newly synthesized molecules (Tyagi, 2012)
To confirm that treatment with tunicamycin induces endoplasmic reticulum stress and activates the unfolded protein response (UPR) in hippocampal cultures, protein extracts from slices maintained in the presence of tunicamycin at either 10 or 80 μg/mL were processed for western blot
We examined the content of p53 by immunofluorescence, and found that Tunicamycin increased the number of p53 positive cells in hippocampal tissue (Figure 8), whereas RECOMBINANT ADENO-ASSOCIATED VIRAL VECTOR SEROTYPE-8 (rAAV8)-Carboxyl Terminus HSP70/90 Interacting Protein (CHIP) prevented the upregulation of p53

Summary

Introduction

Cells present ingenious mechanisms of protein quality control to avoid aggregation of unfolded proteins and to guarantee correct conformation of newly synthesized molecules (Tyagi, 2012). These processes take place in the cytosol, mitochondria and endoplasmic reticulum (ER). ER chaperones bind to nascent polypeptide chains and assist protein folding, while misfolded proteins are directed to proteasomal degradation in the cytosol by endoplasmic reticulum-associated degradation (ERAD) (Hebert and Molinari, 2007; Tsai and Weissman, 2011) Stressful environmental conditions such as increased temperatures, hypoxia, oxidative stress and altered glucose metabolism affect protein folding and derail the homeostasis of the endoplasmic reticulum. UPR activates mechanisms related to ER buffering, such as upregulation of genes involved in protein folding, degradation, and redox regulation, and transient inhibition of global protein translation, which tend to oppose the higher demand for ER function (Hetz, 2012)

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