Pathogenic variants of Valosin‐containing protein induce lysosomal damage and transcriptional activation of autophagy regulators in neuronal cells

Abstract

Aim: Mutations in the valosin-containing protein (VCP) gene cause various lethal proteinopathies that mainly include inclusion body myopathy with Paget's disease of bone and frontotemporal dementia (IBMPFD) and amyotrophic lateral sclerosis (ALS).Different pathological mechanisms have been proposed. Here, we define the impact of VCP mutants on lysosomes and how cellular homeostasis is restored by inducing autophagy in the presence of lysosomal damage.Methods: By electron microscopy, we studied lysosomal morphology in VCP animal and motoneuronal models. With the use of western blotting, real-time quantitative polymerase chain reaction (RT-qPCR), immunofluorescence and filter trap assay, we evaluated the effect of selected VCP mutants in neuronal cells on lysosome size and activity, lysosomal membrane permeabilization and their impact on autophagy.Results: We found that VCP mutants induce the formation of aberrant multilamellar organelles in VCP animal and cell models similar to those found in patients with VCP mutations or with lysosomal storage disorders. In neuronal cells, we found altered lysosomal activity characterised by membrane permeabilization with galectin-3 redistribution

Elamipretide alleviates pyroptosis in traumatically injured spinal cord by inhibiting cPLA2-induced lysosomal membrane permeabilization

“…A previous study has described how LMP and the subsequent release of cathepsin B (CTSB) from lysosomes into the cytosol is a signalling pathway that induces pyroptosis [ 53 ]. Additionally, mounting evidence suggests that lysosomal damage impairs autophagic flux in neural diseases [ 54 , 55 ], such as SCI [ 6 ], and leads to the accumulation of neuronal autophagosomes. Given the significant impact of SS-31 on pyroptosis inhibition and autophagic flux restoration in our research, we hypothesized that SS-31 may affect lysosome function following SCI.…”

“…Researchers have recently started to focus on the role of LMP in CNS trauma [ 6 , 19 , 67 ]. Abundant evidence has shown that lysosomal damage results in neuronal autophagosome accumulation and inhibits autophagic flux in neural diseases [ 54 , 55 ]. Nevertheless, no drug has been found to ameliorate SCI by inhibiting LMP.…”

“…It was recently reported that cPLA2, a phospholipase family member, is required for modulation of autophagy/lysosomal biogenesis and pyroptosis in traumatic CNS injuries [ 6 , 53 , 57 ]. As the primary mediator of neuroinflammation, cPLA2 may break down membrane phosphatides at the sn-2 position to produce lysophospholipids and ω3-polyunsaturated fatty acids, the majority of which are arachidonic acid derivatives and cause further damage [ 54 ]. The lysosomal membrane can also be hydrolysed by cPLA2 under pathological conditions, subsequently leading to LMP.…”

ALS-related p97 R155H mutation disrupts lysophagy in iPSC-derived motor neurons

“…One of these proteins, p62 (SQSTM1), causes multisystem proteinopathy 2 (MSP-2), suggesting that autophagy defects are a common feature in MSPs. Mutations in p97 and inhibition of p97 disrupt autophagy in cells ( Gonzalez et al., 2014 ; Hill et al., 2021 ) and animals ( Ching and Weihl, 2013 ; Ju et al., 2009 ); however, only recently has this disruption been linked to defects in lysophagy ( Ferrari et al., 2022 ; Papadopoulos et al., 2017 ). Multiple components of lysosome repair machinery were common between genetic backgrounds, including annexins (ANXA1, 2, and 11), which were depleted in mutant motor neurons ( Figure 3 E).…”

“…The cellular processes affected by mutant p97 that lead to disease are still intensely debated. Models in immortalized cell types such as U2OS and NSC-34 have found defects in lysophagy leading to an accumulation of damaged lysosomes and increased cell death ( Ferrari et al., 2022 ; Papadopoulos et al., 2017 ). Drosophila and rodent models of p97 disease have shown defects in protein degradation, autophagy, and mitochondrial function ( Gonzalez and Wang, 2020 ; Kim et al., 2013 ; Nalbandian et al., 2012 ).…”