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Huntingtin bodies sequester vesicle-associated proteins by a polyproline-dependent interaction
Zheng-Hong Qin1, Yumei Wang, Ellen Sapp
1Laboratory of Cellular Neurobiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA. zhqin5@hotmail.com
Summary
Mutant huntingtin (htt) forms cytoplasmic bodies, sequestering proteins involved in vesicle trafficking and impairing neuronal function. This mechanism contributes to Huntington's disease pathology.
Area of Science:
- Neuroscience
- Cell Biology
- Genetics
Background:
- Polyglutamine expansion in huntingtin (htt) causes neuronal dysfunction in Huntington's disease.
- The precise mechanisms underlying htt-induced neurodegeneration remain largely unknown.
Purpose of the Study:
- To investigate the cellular mechanisms by which mutant huntingtin causes neuronal dysfunction.
- To characterize the structure and composition of mutant huntingtin aggregates.
Main Methods:
- In vitro expression of truncated huntingtin to form cytoplasmic bodies.
- Protease resistance assays to analyze aggregate core composition.
- Immunohistochemistry to identify protein redistribution in htt bodies.
- Analysis of transferrin uptake to assess vesicle trafficking.
Main Results:
- Mutant htt formed cytoplasmic bodies with a protease-resistant fibrillar core and a protease-sensitive shell.
- The shell contained sequestered proteins involved in vesicle trafficking, including dynamin, HIP1, and proteasome.
- Impaired transferrin internalization was observed in cells forming htt bodies.
- Dynamin accumulated in cytoplasmic bodies in neurons from Huntington's disease patients.
Conclusions:
- Accumulation of nonfibrillar mutant htt in the cytoplasm sequesters essential proteins.
- This sequestration disrupts vesicle trafficking, contributing to neuronal dysfunction in Huntington's disease.
- Targeting htt body formation or protein sequestration may offer therapeutic strategies.