The BPAN and intellectual disability disease proteins WDR45 and WDR45B modulate autophagosome-lysosome fusion

mtSTAT3 suppresses rheumatoid arthritis by regulating Th17 and synovial fibroblast inflammatory cell death with IL-17-mediated autophagy dysfunction

Th17 cells are activated by STAT3 factors in the nucleus, and these factors are correlated with the pathologic progression of rheumatoid arthritis (RA). Recent studies have demonstrated the presence of STAT3 in mitochondria, but its function is unclear. We investigated the novel role of mitochondrial STAT3 (mitoSTAT3) in Th17 cells and fibroblast-like synoviocytes (FLSs) and analyzed the correlation of mitoSTAT3 with RA. We used a collagen-induced arthritis (CIA) mouse model to determine the effect of mitochondrial STAT3. We observed changes in the RA mouse model via the use of a mitochondrial STAT3-inducing vector and inhibitor. We observed the accumulation of abnormal autophagosomes, increased inflammatory cell death signaling, and decreased mitoSTAT3 activity in FLSs from both patients with RA and patients with IL-17-treated FLSs. We first discovered that IL-17 increased the accumulation of abnormal autophagosomes and the expression of inflammatory cell death factors in synovial fibroblasts and decreased mitoSTAT3 activation. In a mouse model of CIA, arthritis and joint inflammation were decreased by injection vectors that induced mitoSTAT3 overexpression. The abnormal accumulation of autophagosomes and the expression of inflammatory cell death factors were also decreased in these mice. In mouse and human immune cells, ZnSO4, an inducer of mitochondrial STAT3, decreases the production of reactive oxygen species, the IL-17 concentration, and differentiation into Th17 cells. However, mitoSTAT3 blockade accelerated the development of arthritis, inflammatory cell death, and abnormal autophagosome/autophagolysosome formation. Therefore, this study suggests a novel inhibitory mechanism of RA using mitoSTAT3 via the regulation of autophagy, Th17 differentiation, and inflammatory cell death.

An update on autophagy disorders

Macroautophagy is a highly conserved cellular pathway for the degradation and recycling of defective cargo including proteins, organelles, and macromolecular complexes. As autophagy is particularly relevant for cellular homeostasis in post-mitotic tissues, congenital disorders of autophagy, due to monogenic defects in key autophagy genes, share a common "clinical signature" including neurodevelopmental, neurodegenerative, and neuromuscular features, as well as variable abnormalities of the eyes, skin, heart, bones, immune cells, and other organ systems, depending on the expression pattern and the specific function of the defective proteins. Since the clinical and genetic resolution of EPG5-related Vici syndrome, the paradigmatic congenital disorder of autophagy, the widespread use of massively parallel sequencing has resulted in the identification of a growing number of autophagy-associated disease genes, encoding members of the core autophagy machinery as well as related proteins. Recently identified monogenic disorders linking selective autophagy, vesicular trafficking, and other pathways have further expanded the molecular and phenotypical spectrum of congenital disorders of autophagy as a clinical disease spectrum. Moreover, significant advances in basic research have enhanced the understanding of the underlying pathophysiology as a basis for therapy development. Here, we review (i) autophagy in the context of other intracellular trafficking pathways; (ii) the main congenital disorders of autophagy and their typical clinico-pathological signatures; and (iii) the recommended primary health surveillance in monogenic disorders of autophagy based on available evidence. We further discuss recently identified molecular mechanisms that inform the current understanding of autophagy in health and disease, as well as perspectives on future therapeutic approaches.

Neurodegeneration with brain iron accumulation 5: report of three cases

Neurodegeneration with brain iron accumulation 5 (NBIA5) is a distinctive type of NBIA phenotype that is caused by mutations in the WDR45 gene. This disorder is inherited in an X-linked manner. Here, we report three Iranian cases affected with this condition. Whole-exome sequencing revealed the following pathogenic variants within WDR45 gene in these cases, respectively: c.697 C > T (p.R233X), c.657_658del (p.F221X) and c.1004_1005del (p.Y335Cfs*5). Hypothyroidism was detected in two cases. Other clinical manifestations did not significantly differ from cases reported in the literature. All cases occurred de novo. Similar mutations have been reported in the literature. The present study broadens the insight about the genetics of this disorder in the mentioned population.

A burning question from the first international BPAN symposium: is restoration of autophagy a promising therapeutic strategy for BPAN?

Beta-propeller protein-associated neurodegeneration (BPAN) is a rare neurodegenerative disease associated with severe cognitive and motor deficits. BPAN pathophysiology and phenotypic spectrum are still emerging due to the fact that mutations in the WDR45 (WD repeat domain 45) gene, a regulator of macroautophagy/autophagy, were only identified a decade ago. In the first international symposium dedicated to BPAN, which was held in Lyon, France, a panel of international speakers, including several researchers from the autophagy community, presented their work on human patients, cellular and animal models, carrying WDR45 mutations and their homologs. Autophagy researchers found an opportunity to explore the defective function of autophagy mechanisms associated with WDR45 mutations, which underlie neuronal dysfunction and early death. Importantly, BPAN is one of the few human monogenic neurological diseases targeting a regulator of autophagy, which raises the possibility that it is a relevant model to directly assess the roles of autophagy in neurodegeneration and to develop autophagy restorative therapeutic strategies for more common disorders.Abbreviations: ATG: autophagy related; BPAN: beta-propeller protein-associated neurodegeneration; ER: endoplasmic reticulum; KO: knockout; NBIA: neurodegeneration with brain iron accumulation; PtdIns3P: phosphatidylinositol-3-phosphate; ULK1: unc-51 like autophagy activating kinase 1; WDR45: WD repeat domain 45; WIPI: WD repeat domain, phosphoinositide interacting.

PTPA variants and impaired PP2A activity in early-onset parkinsonism with intellectual disability

The protein phosphatase 2A complex (PP2A), the major Ser/Thr phosphatase in the brain, is involved in a number of signalling pathways and functions, including the regulation of crucial proteins for neurodegeneration, such as alpha-synuclein, tau and LRRK2. Here, we report the identification of variants in the PTPA/PPP2R4 gene, encoding a major PP2A activator, in two families with early-onset parkinsonism and intellectual disability. We carried out clinical studies and genetic analyses, including genome-wide linkage analysis, whole-exome sequencing, and Sanger sequencing of candidate variants. We next performed functional studies on the disease-associated variants in cultured cells and knock-down of ptpa in Drosophila melanogaster. We first identified a homozygous PTPA variant, c.893T>G (p.Met298Arg), in patients from a South African family with early-onset parkinsonism and intellectual disability. Screening of a large series of additional families yielded a second homozygous variant, c.512C>A (p.Ala171Asp), in a Libyan family with a similar phenotype. Both variants co-segregate with disease in the respective families. The affected subjects display juvenile-onset parkinsonism and intellectual disability. The motor symptoms were responsive to treatment with levodopa and deep brain stimulation of the subthalamic nucleus. In overexpression studies, both the PTPA p.Ala171Asp and p.Met298Arg variants were associated with decreased PTPA RNA stability and decreased PTPA protein levels; the p.Ala171Asp variant additionally displayed decreased PTPA protein stability. Crucially, expression of both variants was associated with decreased PP2A complex levels and impaired PP2A phosphatase activation. PTPA orthologue knock-down in Drosophila neurons induced a significant impairment of locomotion in the climbing test. This defect was age-dependent and fully reversed by L-DOPA treatment. We conclude that bi-allelic missense PTPA variants associated with impaired activation of the PP2A phosphatase cause autosomal recessive early-onset parkinsonism with intellectual disability. Our findings might also provide new insights for understanding the role of the PP2A complex in the pathogenesis of more common forms of neurodegeneration.

Melatonin Induces Autophagy in Amyotrophic Lateral Sclerosis Mice via Upregulation of SIRT1

Amyotrophic lateral sclerosis (ALS) is the neurodegenerative disease that leads to the motor dysfunction damaged by both upper and lower motor neurons. The etiology and pathogenesis of ALS hasn't completely been understood yet up to now, the current study suggests that autophagy plays an important role in the development of ALS. Meanwhile, melatonin is found to inhibit the progression of ALS. To this end, this study aimed to investigate the potential relation between melatonin and autophagy in ALS. The in vivo model of ALS was established to investigate the effects of melatonin in ALS. The mRNA expressions were performed to detect by RT-qPCR, and the protein levels were tested by western blot and immunofluorescence histochemistry staining. The inflammatory cytokine was applied to detect by ELISA. The results showed that melatonin dose-dependently reversed the ALS-induced survival time shortened, weight loss and rotating rod latency decrease. The expressions of both SIRT1 and Beclin-1 as well as the ratio of LC3II/LC3I were significantly upregulated in the ALS mice, while melatonin reversed the upregulation of both SIRT1 and Beclin-1 expression and LC3II/LC3I ratio in a dose-dependent manner. In contrast, melatonin dose-dependently significantly restored the ALS-induced downregulation of p62. Furthermore, SIRT1 silencing notably reduced the effect of melatonin on Beclin-1, LC3II/LC3I, and p62. Melatonin induced autophagy in the ALS mice via the upregulation of SIRT1. Thus, melatonin might act as a new agent for the treatment of ALS.

Weakened interaction of ATG14 and the SNARE complex blocks autophagosome-lysosome fusion contributes to fluoride-induced developmental neurotoxicity

Fluoride is capable of inducing developmental neurotoxicity, but the mechanisms involved remain unclear. We aimed to explore the role of autophagosome-lysosome fusion in developmental fluoride neurotoxicity, particularly focusing on the interaction between ATG14 and the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex. We developed in vivo models of Sprague-Dawley rats exposed to sodium fluoride (NaF) from the pregnancy of parental rats until the offspring were two months old and in vitro models of NaF and/or Ad-ATG14-treated SH-SY5Y cells. We assessed neurobehavioral changes in offspring and further investigated the effects of NaF exposure on autophagic flux, apoptosis, autophagosome-lysosome fusion, and the interaction between ATG14 and the SNARE complex. NaF exposure impaired offspring learning and memory capabilities and induced the accumulation of autophagosomes and autophagic flux blockage and apoptosis, as indicated by increased LC3-II, p62, and cleaved-caspase-3 expression in vivo and in vitro. In addition, NaF treatment downregulated the protein expression of ATG14 and the SNARE complex and induced autophagosome-lysosome fusion blockage as evidenced by decreased ATG14, STX17, SNAP29, and VAMP8 expression and diminished colocalization of autophagosomes and lysosomes in vivo and in vitro. Furthermore, ATG14 upregulation enhanced the interaction of ATG14 and the SNARE complex to facilitate autophagosome-lysosome fusion, thereby restoring autophagic flux and alleviating NaF-induced apoptosis. In conclusion, NaF exhibited developmental neurotoxicity by restraining the interaction of ATG14 with the SNARE complex and hindering autophagosome-lysosome fusion, thereby participating in the occurrence and development of fluoride neurotoxicity. Notably, ATG14 upregulation protects against developmental fluoride neurotoxicity, and ATG14 may serve as a promising biomarker for further epidemiological investigation.