Development of a Polymeric Pharmacological Nanocarrier System as a Potential Therapy for Spinocerebellar Ataxia Type 7.

Spinocerebellar ataxia type 7 (SCA7) is an autosomal-dominant inherited disease characterized by progressive ataxia and retinal degeneration. SCA7 belongs to a group of neurodegenerative diseases caused by an expanded CAG repeat in the disease-causing gene, resulting in aberrant polyglutamine (polyQ) protein synthesis. PolyQ ataxin-7 is prone to aggregate in intracellular inclusions, perturbing cellular processes leading to neuronal death in specific regions of the central nervous system (CNS). Currently, there is no treatment for SCA7; however, a promising approach successfully applied to other polyQ diseases involves the clearance of polyQ protein aggregates through pharmacological activation of autophagy. Nonetheless, the blood-brain barrier (BBB) poses a challenge for delivering drugs to the CNS, limiting treatment effectiveness. This study aimed to develop a polymeric nanocarrier system to deliver therapeutic agents across the BBB into the CNS. We prepared poly(lactic-co-glycolic acid) nanoparticles (NPs) modified with Poloxamer188 and loaded with rapamycin to enable NPs to activate autophagy. We demonstrated that these rapamycin-loaded NPs were successfully taken up by neuronal and glial cells, demonstrating high biocompatibility without adverse effects. Remarkably, rapamycin-loaded NPs effectively cleared mutant ataxin-7 aggregates in a SCA7 glial cell model, highlighting their potential as a therapeutic approach to fight SCA7 and other polyQ diseases.

SEL1L degradation intermediates stimulate cytosolic aggregation of polyglutamine-expanded protein.

Misfolded proteins in the endoplasmic reticulum (ER) are degraded by ER-associated degradation (ERAD). In mammalian cells, the HRD1-SEL1L membrane ubiquitin ligase complex plays a central role in this process. However, SEL1L is inherently unstable, and excess SEL1L is also degraded by ERAD. Accordingly, when proteasome activity is inhibited, multiple degradation intermediates of SEL1L appear in the cytosol. In this study, we searched for factors that inhibit SEL1L degradation and identified OS-9 and XTP3-B, two ER lectins that regulate glycoprotein ERAD. SEL1L degradation was characterized by a ladder of degradation products, and the C-terminal Pro-rich region of SEL1L was responsible for generation of this pattern. In the cytosol, these degradation intermediates stimulated aggregation of polyglutamine-expanded Huntingtin protein (Htt-polyQ-GFP) by interacting with aggregation-prone proteins, including Htt-polyQ-GFP. Collectively, our findings indicate that peptide fragments of ER proteins generated during ERAD may affect protein aggregation in the cytosol, revealing the interconnection of protein homeostasis across subcellular compartments.

The indole compound NC009-1 inhibits aggregation and promotes neurite outgrowth through enhancement of HSPB1 in SCA17 cells and ameliorates the behavioral deficits in SCA17 mice.

Spinocerebellar ataxia type 17 (SCA17) is caused by the expansion of translated CAG repeat in the TATA box binding protein (TBP) gene encoding a long polyglutamine (polyQ) tract in the TBP protein, which leads to intracellular accumulation of aggregated TBP and cell death. The molecular chaperones act in preventing protein aggregation to ameliorate downstream harmful events. In this study, we used Tet-On cells with inducible SCA17 TBP/Q79-GFP expression to test five in-house NC009 indole compounds for neuroprotection. We found that both aggregation and polyQ-induced reactive oxygen species can be significantly prohibited by the tested NC009 compounds in Tet-On TBP/Q79 293 cells. Among the five indole compounds, NC009-1 up-regulated expression of heat shock protein family B (small) member 1 (HSPB1) chaperone to reduce polyQ aggregation and promote neurite outgrowth in neuronal differentiated TBP/Q79 SH-SY5Y cells. The increased HSPB1 thus ameliorated the increased BH3 interacting domain death agonist (BID), cytochrome c (CYCS) release, and caspase 3 (CASP3) activation which result in apoptosis. Knock down of HSPB1 attenuated the effects of NC009-1 on TBP/Q79 SH-SY5Y cells, suggesting that HSPB1 might be one of the major pathways involved for NC009-1 effects. NC009-1 further reduced polyQ aggregation in Purkinje cells and ameliorated behavioral deficits in SCA17 TBP/Q109 transgenic mice. Our results suggest that NC009-1 has a neuroprotective effect on SCA17 cell and mouse models to support its therapeutic potential in SCA17 treatment.

Hormetic heat shock and HSF-1 overexpression improve C. elegans survival and proteostasis by inducing autophagy.

The cellular recycling process of macroautophagy/autophagy is an essential homeostatic system induced by various stresses, but it remains unclear how autophagy contributes to organismal stress resistance. In a recent study, we report that a mild and physiologically beneficial ("hormetic") heat shock as well as overexpression of the heat-shock responsive transcription factor HSF-1 systemically increases autophagy in C. elegans. Accordingly, we found HSF-1- and heat stress-inducible autophagy to be required for C. elegans thermoresistance and longevity. Moreover, a hormetic heat shock or HSF-1 overexpression alleviated PolyQ protein aggregation in an autophagy-dependent manner. Collectively, we demonstrate a critical role for autophagy in C. elegans stress resistance and hormesis, and reveal a requirement for autophagy in HSF-1 regulated functions in the heat-shock response, proteostasis, and aging.

Indole and synthetic derivative activate chaperone expression to reduce polyQ aggregation in SCA17 neuronal cell and slice culture models.

In spinocerebellar ataxia type 17 (SCA17), the expansion of a translated CAG repeat in the TATA box binding protein (TBP) gene results in a long polyglutamine (polyQ) tract in the TBP protein, leading to intracellular accumulation of aggregated TBP and cell death. The molecular chaperones act in preventing protein aggregation to ameliorate downstream harmful events. In this study, we used Tet-On SH-SY5Y cells with inducible SCA17 TBP/Q79-green fluorescent protein (GFP) expression to test indole and synthetic derivative NC001-8 for neuroprotection. We found that indole and NC001-8 up-regulated chaperone expression to reduce polyQ aggregation in neuronal differentiated TBP/Q79 cells. The effects on promoting neurite outgrowth and on reduction of aggregation on Purkinje cells were also confirmed with cerebellar primary and slice cultures of SCA17 transgenic mice. Our results demonstrate how indole and derivative NC001-8 reduce polyQ aggregation to support their therapeutic potentials in SCA17 treatment.