The Unfolded Protein Response in Homeostasis and Modulation of Mammalian Immune Cells

Abstract

The endoplasmic reticulum (ER) plays important roles in eukaryotic protein folding and lipid biosynthesis. Several exogenous and endogenous cellular sources of stress can perturb ER homeostasis leading to the accumulation of unfolded proteins in the lumen. Unfolded protein accumulation triggers a signal-transduction cascade known as the unfolded protein response (UPR), an adaptive mechanism which aims to protect cells from protein aggregates and to restore ER functions. Further to this protective mechanism, in immune cells, UPR molecular effectors have been shown to participate in a wide range of biological processes such as cell differentiation, survival and immunoglobulin and cytokine production. Recent findings also highlight the involvement of the UPR machinery in the maturational program and antigen presentation capacities of dendritic cells. UPR is therefore a key element in immune system homeostasis with direct implications on both adaptive and innate immune responses. The present review summarizes the knowledge on the emerging roles of UPR signaling cascades in mammalian immune cells as well as the consequences of their dysregulation in relation to the pathogenesis of several diseases.

Keywords :

• Endoplasmic reticulum stress
• unfolded protein response
• immune cells
• IRE1
• ATF6
• PERK
• Regulated Ire1-Dependent Decay

FUNDING

This work was supported by Federal funds through Programa Operacional Temático Factores de Competitividade (COMPETE) with co-participation from the European Community Fund (FEDER) and national funds through Fundação para a Ciência e Tecnologia (FCT) under the project PTDC/SAU-ONC/118346/2010. Thanks are due to FCT/MEC for the financial support to the QOPNA research Unit (FCT UID/QUI/00062/2013), through national founds and where applicable co-financed by the FEDER, within the PT2020 Partnership Agreement, and also to the Portuguese NMR Network. The Institute for Biomedicine—UID/BIM/04501/2013 is acknowledged.

Declaration of Interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.