Attenuation of endoplasmic reticulum stress in Pelizaeus-Merzbacher disease by an anti-malaria drug, chloroquine

Abstract

Pelizaeus-Merzbacher disease (PMD) is a hypomyelinating disorder caused by the duplication and missense mutations of the proteolipid protein 1 (PLP1) gene. PLP1 missense proteins accumulate in the endoplasmic reticulum (ER) of premature oligodendrocytes and induce severe ER stress followed by apoptosis of the cells. Here, we demonstrate that an anti-malaria drug, chloroquine, decreases the amount of an ER-resident mutant PLP1 containing an alanine-243 to valine (A243V) substitution, which induces severe PMD in human. By preventing mutant PLP1 translation through enhancing the phosphorylation of eukaryotic initiation factor 2 alpha, chloroquine ameliorated the ER stress induced by the mutant protein in HeLa cells. Chroloquine also attenuated ER stress in the primary oligodendrocytes obtained from myelin synthesis deficit (msd) mice, which carry the same PLP1 mutation. In the spinal cords of msd mice, chloroquine inhibited ER stress and upregulated the expression of marker genes of mature oligodendrocytes. Chloroquine-mediated attenuation of ER stress was observed in HeLa cells treated with tunicamycin, an N-glycosylation inhibitor, but not with thapsigargin, a sarco/ER Ca(2+)ATPase inhibitor, which confirms its efficacy against ER stress caused by nascent proteins. These findings indicate that chloroquine is an ER stress attenuator with potential use in treating PMD and possibly other ER stress-related diseases.

Cellular Pathology of Pelizaeus-Merzbacher Disease Involving Chaperones Associated with Endoplasmic Reticulum Stress

“…Chloroquine, an anti-malarial drug, was found to reduce the accumulation of the mutant PLP1 and attenuate ER stress by enhancing the phosphorylation of eIF2α (Morimura et al, 2014 ). Despite its drastic effects as an ER stress attenuator, the concentration to obtain this effect in vitro was relatively high (100 μM) for clinical application, considering its side effects.…”

Knockdown of Rab7B, But Not of Rab7A, Which Antagonistically Regulates Oligodendroglial Cell Morphological Differentiation, Recovers Tunicamycin-Induced Defective Differentiation in FBD-102b Cells

“…This nding reminded us of the possibility that knockdown of Rab7B recovers diseaseassociated undifferentiated states. As expected, Rab7B knockdown recovered undifferentiated morphologies induced by treatment with tunicamycin, which mimics endoplasmic reticulum (ER) stress [21,22]. It is thought that ER stress is one of the major pathological causes observed in Pelizaeus-Merzbacher disease (PMD, also called hypomyelinating leukodystrophy 1 [HLD1]) and some other neuropathies [12,23,24].…”

“…The results pertaining to the effects of Rab7B on morphological differentiation suggested the possibility that knockdown of Rab7B could help recover the inhibitory morphological differentiation in disease states [25,26]. We induced ER stress using tunicamycin [21,22] and mimicked cellular disease states, as often observed in oligodendroglial cell diseases [23,24] and many other neurological diseases [11,12]. In fact, tunicamycin inhibited morphological differentiation in a dose-dependent manner in FBD-102b cells (Figure S2).…”

“…PMD is associated with various gene mutations, including ampli cation of the plp1 gene encoding major myelin plasma membrane protein, resulting in PLP1 accumulating in the ER. It is thought that the misfolded PLP1 proteins trigger ER stress, causing cell pathological phenotypes of oligodendropathies [21,23,25,26]. One of the phenotypes results in the increase of undifferentiated and/or hypomyelinating oligodendroglial cells.…”

Four specific biomarkers associated with the progression of glioblastoma multiforme in older adults identified using weighted gene co-expression network analysis

“…PLP1 encodes a protein with 276 amino acids, which is the most abundant myelin protein in the brain and can regulate myelin lamellar spacing/compaction and maintain axonal integrity via oligodendrocyte-axonal interactions [ 31 ]. Previous studies revealed that overexpression of PLP1 enhanced the accumulation of lipids in the myelin sheath, thereby promoting the progression of diseases in the central nervous system, such as Pelizaeus-Merzbacher disease [ 32 , 33 ]. Furthermore, PLP1 has the potential to inhibit the endoplasmic reticulum [ 34 ].…”