Sacsin Deletion Induces Aggregation of Glial Intermediate Filaments

Abstract

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a neurodegenerative disorder commonly diagnosed in infants and characterized by progressive cerebellar ataxia, spasticity, motor sensory neuropathy and axonal demyelination. ARSACS is caused by mutations in the SACS gene that lead to truncated or defective forms of the 520 kDa multidomain protein, sacsin. Sacsin function is exclusively studied on neuronal cells, where it regulates mitochondrial network organization and facilitates the normal polymerization of neuronal intermediate filaments (i.e., neurofilaments and vimentin). Here, we show that sacsin is also highly expressed in astrocytes, C6 rat glioma cells and N9 mouse microglia. Sacsin knockout in C6 cells (C6Sacs−/−) induced the accumulation of the glial intermediate filaments glial fibrillary acidic protein (GFAP), nestin and vimentin in the juxtanuclear area, and a concomitant depletion of mitochondria. C6Sacs−/− cells showed impaired responses to oxidative challenges (Rotenone) and inflammatory stimuli (Interleukin-6). GFAP aggregation is also associated with other neurodegenerative conditions diagnosed in infants, such as Alexander disease or Giant Axonal Neuropathy. Our results, and the similarities between these disorders, reinforce the possible connection between ARSACS and intermediate filament-associated diseases and point to a potential role of glia in ARSACS pathology.

AlphaFold predicted structure of the Hsp90-like domains of the neurodegeneration linked protein sacsin reveals key residues for ATPase activity

“…Moreover, significant reorganisation of the intermediate filament cytoskeleton is observed in sacsin null cells (Girard et al, 2012b;Lariviere et al, 2015;Bradshaw et al, 2016;Duncan et al, 2017;Gentil et al, 2019). This includes the formation of perinuclear accumulations of vimentin in sacsin knockout SH-SY5Y cells and ARSACS patient dermal fibroblasts (Duncan et al, 2017), as well as abnormal bundling of non-phosphorylated neurofilament in neurons from sacsin knockout mice (Lariviere et al, 2015) and aggregation of glial fibrillary acidic protein in glial cells (Murtinheira et al, 2022). Unexpectedly, heterologous expression of isolated sacsin domains can modulate neurofilament assembly (Lariviere et al, 2015).…”

AlphaFold predicted structure of the Hsp90-like domains of the neurodegeneration linked protein sacsin reveals key residues for ATPase activity

“…Significant reorganisation of the intermediate filament cytoskeleton is observed in sacsin null cells [11,13,14,16,17]. This includes the formation of perinuclear accumulations of vimentin in sacsin knockout SH-SY5Y cells and ARSACS patient dermal fibroblasts [16], as well as abnormal bundling of non-phosphorylated neurofilament in neurons from sacsin knockout mice [17] and aggregation of glial fibrillary acidic protein in glial cells [31]. Unexpectedly, heterologous expression of isolated sacsin domains can modulate neurofilament assembly [17].…”

Asymmetric post-translational modifications regulate the nuclear translocation of STAT3 homodimers in response to leukemia inhibitory factor

“…Here, we corrected these issues to con rm or reject the original hypothesis. We developed a STAT3-/-HeLa strain using commercially available CRISPR/Cas9 (sc-400027, Santa Cruz Biotechnologies, Dallas, TX), cell sorting and clonal selection procedures described elsewhere [13]. Cells were maintained and seeded as described previously [12,13].…”

“…We developed a STAT3-/-HeLa strain using commercially available CRISPR/Cas9 (sc-400027, Santa Cruz Biotechnologies, Dallas, TX), cell sorting and clonal selection procedures described elsewhere [13]. Cells were maintained and seeded as described previously [12,13]. This new HeLa strain does not express endogenous STAT3.…”