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Updated: May 6, 2026
Fractionation for Resolution of Soluble and Insoluble Huntingtin Species
Published on: February 27, 2018
Neuronal mitochondrial disaggregase CLPB ameliorates Huntington's disease pathology in mice
Hyeonho Kim1,2, Gaeun Hyun1, Seunghye Kim1,2
1Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea.
Insights
Caseinolytic peptidase B (ClpB) helps manage huntingtin protein (HTT) aggregation and maintains synaptic health in Huntington
Area of Science:
- Neurodegenerative Diseases
- Molecular Biology
- Mitochondrial Function
Background:
- Huntington's disease (HD) stems from CAG repeat expansion in the HTT gene, leading to toxic polyglutamine-expanded huntingtin (HTT) protein aggregates.
- The role of heat-shock proteins, like caseinolytic peptidase B (ClpB), in modulating protein aggregation and proteostasis in HD is not fully understood.
- Investigating ClpB's function in maintaining synaptic integrity within the context of HD pathology is crucial.
Purpose of the Study:
- To investigate the role of caseinolytic peptidase B (ClpB) in regulating huntingtin protein (HTT) aggregation.
- To determine ClpB's impact on synaptic integrity and mitochondrial proteostasis in Huntington's disease models.
- To explore ClpB as a potential therapeutic target for neurodegenerative disorders.
Main Methods:
- Examined the effect of CLPB gene knockout and overexpression on wild-type (HTT-Q23) and mutant (HTT-Q79) huntingtin aggregation in HEK293T cells.
- Utilized adeno-associated virus (AAV)-mediated gene transfer to modulate ClpB levels in the striatum of HD model mice.
- Assessed HTT aggregation, inhibitory synapse density (VGAT immunohistochemistry), and synaptic transmission (electrophysiology).
Main Results:
- CLPB knockout increased HTT-Q23 aggregation; ClpB overexpression reduced HTT-Q79 aggregate size in cell models.
- In HD mice, ClpB knockdown worsened HTT aggregation, while ClpB overexpression restored inhibitory synapse density and function.
- ClpB overexpression correlated with reduced mitochondrial aggregation, indicating a role in mitochondrial protein quality control.
Conclusions:
- ClpB plays a significant role in regulating both normal and pathological HTT aggregation.
- ClpB is vital for maintaining inhibitory synaptic integrity and function in Huntington's disease.
- ClpB acts protectively in HD by modulating mitochondrial proteostasis, suggesting therapeutic potential.
Abstract:
Background: Huntington's disease (HD) is a devastating neurodegenerative disorder caused by CAG repeat expansion in the HTT gene, resulting in a polyglutamine-expanded huntingtin (HTT) protein that forms toxic aggregates. Although heat-shock proteins are known to facilitate the refolding or clearance of misfolded proteins, their precise role in modulating protein aggregation in HD remains unclear. Here, we explore the function of caseinolytic peptidase B (ClpB), a mitochondrial AAA+ ATPase and heat-shock protein, in maintaining proteostasis and synaptic integrity in HD. Methods: We examined how CLPB loss or overexpression in human embryonic kidney 293T (HEK293T) cells impacted the aggregation of wild-type HTT (HTT-Q23) and mutant HTT (HTT-Q79). In parallel, AAV-mediated ClpB knockdown or overexpression was applied to the striatum of HD model mice. and HTT aggregation and inhibitory synaptic alterations were assessed. Aggregate burden was quantified via immunostaining, and inhibitory synapse density was evaluated using VGAT immunohistochemistry and electrophysiological recordings. Results: In HEK293T cells, CLPB knockout led to abnormal aggregation of HTT-Q23 while CLPB overexpression reduced the size of HTT-Q79 aggregates. In the mouse striatum, ClpB knockdown increased HTT-Q23 aggregate numbers and altered HTT-Q79 aggregation morphology, whereas CLPB overexpression restored the density and size of VGAT-positive inhibitory synapses and improved inhibitory synaptic transmission in HD model mice. These effects of CLPB overexpression were associated with a reduced mitochondrial aggregation burden, suggesting that ClpB contributes to mitochondrial protein quality control. Conclusions: These results demonstrate that ClpB regulates both physiological and pathological HTT aggregation and contributes to maintaining inhibitory synaptic integrity. By modulating mitochondrial proteostasis, ClpB acts as a protective factor in HD pathology, highlighting its potential as a therapeutic target for neurodegenerative disorders characterized by protein misfolding.
