Mechanism of impaired microtubule-dependent peroxisome trafficking and oxidative stress in SPAST-mutated cells from patients with Hereditary Spastic Paraplegia

Abstract

Hereditary spastic paraplegia (HSP) is an inherited neurological condition that leads to progressive spasticity and gait abnormalities. Adult-onset HSP is most commonly caused by mutations in SPAST, which encodes spastin a microtubule severing protein. In olfactory stem cell lines derived from patients carrying different SPAST mutations, we investigated microtubule-dependent peroxisome movement with time-lapse imaging and automated image analysis. The average speed of peroxisomes in patient-cells was slower, with fewer fast moving peroxisomes than in cells from healthy controls. This was not because of impairment of peroxisome-microtubule interactions because the time-dependent saltatory dynamics of movement of individual peroxisomes was unaffected in patient-cells. Our observations indicate that average peroxisome speeds are less in patient-cells because of the lower probability of individual peroxisome interactions with the reduced numbers of stable microtubules: peroxisome speeds in patient cells are restored by epothilone D, a tubulin-binding drug that increases the number of stable microtubules to control levels. Patient-cells were under increased oxidative stress and were more sensitive than control-cells to hydrogen peroxide, which is primarily metabolised by peroxisomal catalase. Epothilone D also ameliorated patient-cell sensitivity to hydrogen-peroxide. Our findings suggest a mechanism for neurodegeneration whereby SPAST mutations indirectly lead to impaired peroxisome transport and oxidative stress.

Spastin tethers lipid droplets to peroxisomes and directs fatty acid trafficking through ESCRT-III

“…Depletion of Spastin in Drosophila and C. elegans leads to aberrant FA metabolism in LDs (Papadopoulos et al, 2015). In addition, HSP patient-derived olfactory neurosphere-derived cells with mutations in Spastin showed impaired peroxisome movement and distribution (Wali et al, 2016). This coincided with increased cellular lipid peroxidation and reduced energy production, possibly caused by defective FA trafficking to peroxisomes.…”

Serum neurofilament light chain is increased in hereditary spastic paraplegias

“…However, biomarkers indicating neuronal damage in HSP are warranted, as disease‐modifying treatment options are coming within reach, necessitating objective treatment‐outcome parameters. For example, genotype‐specific treatment trials have come into reach for HSP subtypes SPG5 and SPG4, warranting the development of easily accessible peripheral biomarkers.…”

The mitochondrial Rho-GTPase, Miro, is resident at peroxisomes and regulates peroxisomal trafficking and morphology

“…As peroxisomes are involved in a diverse range of metabolic functions and the fact that they interact with several organelles (Shai et al, 2016), peroxisomes must be trafficked throughout the cell. The importance of this has been emphasised by SPAST mutant (associated with hereditary spastic paraplegia) cells exhibiting reduced peroxisomal trafficking and subsequently defects in distribution, resulting in impaired handling of ROS (Abrahamsen et al, 2013;Wali et al, 2016). The current paradigm of peroxisomal trafficking in mammalian cells is that ~5-15% of peroxisomes undergo long-range microtubule-dependent trafficking, with the rest exhibiting shorter-range displacements, often referred to as oscillatory motility.…”