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Heavy meromyosin labeling of intermediate filaments in cultured connective tissue cells
Abstract:
Mild treatment with trypsin causes a radical change in the heavy meromyosin (HMM) binding properties of intermediate filaments in glycerinated, myosin-extracted cultured chick embryo connective tissue cells. In non-trypsin-treated cells, HMM labeling of filaments was often indistinct and variable in its distribution. By contrast, in cells treated with trypsin (under conditions which allowed most intermediate filaments to survive), virtually all filaments, including those of intermediate size, decorated with HMM to give distinct arrowhead patterns. We suggest that most intermediate filaments in such cells contain a core of F-actin masked by trypsin-labile accessory proteins.
Insights
Mild trypsin treatment dramatically alters how heavy meromyosin (HMM) binds to intermediate filaments in cultured cells. This reveals a masked F-actin core within these filaments, crucial for understanding cell structure.
Area of Science:
- Cell Biology
- Biochemistry
- Cytoskeleton Dynamics
Background:
- Intermediate filaments are key cytoskeletal components.
- Their interaction with actin is not fully understood.
- Heavy meromyosin (HMM) is used to probe actin structure.
Purpose of the Study:
- To investigate the effect of mild trypsin treatment on intermediate filament binding properties.
- To characterize the structural components of intermediate filaments.
- To explore the relationship between intermediate filaments and F-actin.
Main Methods:
- Glycerination and myosin extraction of cultured chick embryo connective tissue cells.
- Mild trypsin treatment of cells.
- Heavy meromyosin (HMM) labeling and visualization of intermediate filaments.
- Microscopic analysis of filament decoration patterns.
Main Results:
- Non-trypsin-treated cells showed indistinct and variable HMM labeling of filaments.
- Trypsin-treated cells exhibited distinct arrowhead patterns of HMM decoration on nearly all intermediate filaments.
- These findings suggest trypsin-labile accessory proteins mask a core of F-actin.
Conclusions:
- Mild trypsin treatment unmasks F-actin within intermediate filaments.
- Intermediate filaments likely contain a trypsin-labile protein layer covering an F-actin core.
- This study provides new insights into the composition and structure of intermediate filaments.