Stress-inducible phosphoprotein 1 (HOP/STI1/STIP1) regulates the accumulation and toxicity of α-synuclein in vivo

Abstract

The predominantly pre-synaptic intrinsically disordered protein α-synuclein is prone to misfolding and aggregation in synucleinopathies, such as Parkinson’s disease (PD) and Dementia with Lewy bodies (DLB). Molecular chaperones play important roles in protein misfolding diseases and members of the chaperone machinery are often deposited in Lewy bodies. Here, we show that the Hsp90 co-chaperone STI1 co-immunoprecipitated α-synuclein, and co-deposited with Hsp90 and Hsp70 in insoluble protein fractions in two mouse models of α-synuclein misfolding. STI1 and Hsp90 also co-localized extensively with filamentous S129 phosphorylated α-synuclein in ubiquitin-positive inclusions. In PD human brains, STI1 transcripts were increased, and in neurologically healthy brains, STI1 and α-synuclein transcripts correlated. Nuclear Magnetic Resonance (NMR) analyses revealed direct interaction of α-synuclein with STI1 and indicated that the STI1 TPR2A, but not TPR1 or TPR2B domains, interacted with the C-terminal domain of α-synuclein. In vitro, the STI1 TPR2A domain facilitated S129 phosphorylation by Polo-like kinase 3. Moreover, mice over-expressing STI1 and Hsp90ß presented elevated α-synuclein S129 phosphorylation accompanied by inclusions when injected with α-synuclein pre-formed fibrils. In contrast, reduced STI1 function decreased protein inclusion formation, S129 α-synuclein phosphorylation, while mitigating motor and cognitive deficits as well as mesoscopic brain atrophy in α-synuclein-over-expressing mice. Our findings reveal a vicious cycle in which STI1 facilitates the generation and accumulation of toxic α-synuclein conformers, while α-synuclein-induced proteostatic stress increased insoluble STI1 and Hsp90.

Presymptomatic neuroanatomical and cognitive biomarkers of alpha-synuclein propagation in a mouse model of synucleinopathy

“…Given the brain regions affected by atrophy in PFF-injected mice (cortical-striatal and thalamic networks), we anticipated that executive function, and in particular behavioural flexibility and reversal learning (64–66), could provide a cognitive correlate that reflects aSyn misfolding and spreading. Indeed, recent work suggest that aSyn toxicity in M83 homozygous mice triggers reversal learning, but not attentional deficits (67). Since we observed no sex differences in our imaging findings, we chose to focus this experiment on male mice, given the predominance of PD in men and because of the higher statistical power needed to study sex as a biological variable in behaviour performance (45, 67).…”

“…Indeed, recent work suggest that aSyn toxicity in M83 homozygous mice triggers reversal learning, but not attentional deficits (67). Since we observed no sex differences in our imaging findings, we chose to focus this experiment on male mice, given the predominance of PD in men and because of the higher statistical power needed to study sex as a biological variable in behaviour performance (45, 67). We tested mice longitudinally (49±7 and 84±7 dpi) using pairwise visual discrimination and reversal learning (PVD-R, 45) in two independent cohorts of PFF- or PBS-injected M83 hemizygous mice (Figure 4A-K) using two different sets of images; one set in which the images are more easily differentiable (Figure 4F-H) and a second set in which the images are harder to differentiate (Figure 4I-K).…”

“…An alternate mouse model of PD (6-OHDA injected C57BL/6N mice) was tested in touchscreens and found to have attention deficits, but not reversal learning deficits (81). Conversely, with the M83 model, recent experiments by our group suggest that toxic aSyn in homozygous M83 mice (not injected with PFFs, which spontaneous develop disease around a year of age) leads also to reversal learning deficits but not attention deficits (67). Moreover, in this work, reducing the load of aSyn misfolding (with the introduction of a chaperone transgene) mitigated these behavioural deficits and resulted in milder patterns of MRI-derived atrophy in the brain.…”

Genetic inactivation of the USP19 deubiquitinase regulates a-synuclein ubiquitination and inhibits accumulation of Lewy body like aggregates in mice

“…Monomeric a-syn (5 mg/ml) was allowed to spontaneously form fibrillar aggregates at 37°C in an orbital shaker for 5 days at 1,000 RPM. Quality control was assessed per batch using TEM to examine fibrillar morphology after negative staining, and Thioflavin-T assay to verify formation of amyloid fibrils, which were then sonicated by 40 cycles of 30 sec ON-OFF on a Bioruptor Pico (Denville, NJ) to yield fibrils of 50 to 100 nm long in hydrodynamic diameter as shown by dynamic light scattering 30,77 . Sonicated fibrils were aliquoted and stored at -80°C for short (which was not certified by peer review) is the author/funder.…”

Cerebrospinal fluid and blood profiles of transfer RNA fragments show age, sex, and Parkinson's disease‐related changes

“…Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder, showing both motor and non‐motor symptoms (Schapira et al, 2017). Other symptoms of PD are the cholinergic‐dopaminergic imbalance in the brain (Bohnen et al, 2015; McKinley et al, 2019), as well as neuroinflammation evident in the Substantia Nigra and in blood RNA markers of inflammatory pathways (Craig et al, 2021a; Lackie et al, 2022; López et al, 2016; Winek et al, 2020). Therefore, we set out to seek these characteristics in healthy male and female individuals along age and with or without Parkinson's disease (PD).…”