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Aggregation of misfolded proteins can be a selective process dependent upon peptide composition
Michal I Milewski1, John E Mickle, John K Forrest
1Institute of Genetic Medicine, Johns Hopkins University School of Medicine, 600 N. Wolfe Street, Baltimore, MD 21287, USA.
The Journal of Biological Chemistry
|June 27, 2002
Summary
Protein aggregation, implicated in diseases like cystic fibrosis, is sequence-specific. Modifying just two amino acids in a CFTR peptide prevents aggregation and alters its cellular location, revealing selective intracellular accumulation mechanisms.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Intracellular protein aggregation is a hallmark of various human diseases, particularly neurodegenerative disorders.
- Expanded polyglutamine tracts are central to many such disorders, but the sequence-specific nature of aggregation remains poorly understood.
- Protein mutations can lead to aggregation, suggesting it's a common pathogenic mechanism in inherited disorders.
Purpose of the Study:
- To investigate the relationship between peptide sequence and the specificity of intracellular protein accumulation.
- To determine if specific amino acid residues influence protein aggregation and localization within the cell.
- To explore the impact of reporter protein fusion on the aggregation and distribution of disease-related peptides.
Main Methods:
- Site-directed mutagenesis was used to substitute two residues in a 111-amino acid peptide from the cystic fibrosis transmembrane conductance regulator (CFTR).
- Fusion proteins were created by linking the CFTR peptide fragment (amino acids 1370-1480) to green fluorescent protein (GFP).
- Subcellular localization and aggregation patterns were analyzed using microscopy, and co-expression studies were performed with other aggregating proteins.
Main Results:
- Substitution of two specific amino acids abolished aggregation of the CFTR-derived peptide.
- Fusion to GFP caused the CFTR peptide to accumulate in large perinuclear or nuclear aggregates, while the unfused peptide localized to mitochondria.
- Both aggregation patterns were dependent on the identified two amino acids, and the CFTR peptides did not co-aggregate with huntingtin fragments.
Conclusions:
- Intracellular protein aggregation is a selective process dictated by the specific amino acid sequence of the aggregating peptide.
- The cellular localization and aggregation propensity of peptides can be significantly altered by sequence modifications and fusion to other proteins.
- These findings provide insights into the molecular mechanisms underlying proteinopathies and potential therapeutic targets.