Antioxidative CXXC Peptide Motif From Mesencephalic Astrocyte-Derived Neurotrophic Factor Antagonizes Programmed Cell Death.

Valentina Božok,Urmas Arumäe,Li-ying Yu,Jaan Palgi

doi:10.3389/fcell.2018.00106

Abstract

Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a potent survival-promoting protein with neurorestorative effect for neurodegenerative diseases. Its mechanism of action, albeit poorly known, depends strongly on the CXXC motif (CKGC). Here we studied the survival-promoting properties of the CKGC tetrapeptide from MANF. In the Jurkat T lymphocytic cell line, CKGC potently inhibits death receptor Fas-induced apoptosis and mildly counteracts mitochondrial apoptosis and necroptosis. The peptide with serines instead of cysteines (SKGS) has no survival-promoting activity. The cytoprotective efficiency of the peptide against Fas-induced apoptosis is significantly improved by reduction of its cysteines by dithiotreitol, suggesting that it protects the cells via cysteine thiol groups, partially as an antioxidant. CKGC neutralizes the reactive oxygen species, maintains the mitochondrial membrane potential and prevents activation of the effector caspases in the Jurkat cells with activated Fas. The peptide does not require intracellular administration, as it is endocytosed and resides mainly in the Golgi. Finally, the peptide also potently promotes survival of cultured primary dopaminergic neurons.

Highlights

Programmed cell death is an essential process to remove unwanted or damaged cells, both in physiological and pathological situations
In this study we focused on death receptor-dependent apoptosis, CKGC peptide has a wider range of activity being able to counteract mitochondrial apoptosis and necroptosis
We killed Jurkat cells via different ways: classical apoptosis induced with etoposide, death receptor-dependent apoptosis induced by agonistic antibody CH11 to Fas receptor, and necroptosis achieved by activation of Fas receptor for a long time (72 h) in the presence of pan-caspase inhibitor Q-VD-Oph

Summary

Introduction

Programmed cell death is an essential process to remove unwanted or damaged cells, both in physiological and pathological situations. Cells can die via several death programs, including mitochondrial or death receptor-mediated apoptosis (Lavrik, 2014). Apoptosis is irreversible when caspases, the proteases that cause cellular demise, are activated above certain threshold. Caspases are activated by the proteins, such as cytochrome c, Smac/Diablo, etc., that are released from the mitochondria to cytosol (Estaquier et al, 2012; Tait and Green, 2013). In the death receptor mediated apoptosis, caspases are activated at the cytoplasmic domains of the ligated death receptors, such as Fas, TNF-α, and TRAIL (Lavrik and Krammer, 2012; Wajant, 2014). Cells can die via non-apoptotic programs, such as necroptosis that can be activated mostly in pathological

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