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Cytoskeletal integrity in interphase cells requires protein phosphatase activity
J E Eriksson1, D L Brautigan, R Vallee
1Department of Cell, Molecular, and Structural Biology, Northwestern University Medical School, Chicago, IL 60611-3008.
Summary
Protein phosphatases are crucial for maintaining cytoskeletal structure, including intermediate filaments and microtubules. Inhibiting these enzymes rapidly alters cell structure and vimentin phosphorylation, highlighting their essential role in cytoskeletal integrity.
Area of Science:
- Cell Biology
- Biochemistry
Background:
- Protein kinases regulate cytoskeletal structure through phosphorylation.
- The role of protein phosphatases in cytoskeletal regulation is largely unknown.
Purpose of the Study:
- To investigate the function of protein phosphatases in cytoskeletal regulation.
- To assess the effects of phosphatase inhibitors on fibroblast cytoskeletal organization.
Main Methods:
- BHK-21 fibroblasts were treated with phosphatase inhibitors: calyculin A, okadaic acid, and dinophysistoxin 1.
- Immunofluorescence was used to assay cytoskeletal structure (intermediate filaments and microtubules).
- Vimentin phosphorylation was analyzed to assess biochemical changes.
Main Results:
- Incubation with phosphatase inhibitors rapidly altered intermediate filament organization and led to microtubule loss.
- These structural changes were accompanied by a selective increase in vimentin phosphorylation at interphase-specific sites.
- The observed cytoskeletal alterations were fully reversible upon removal of calyculin A.
Conclusions:
- There is rapid phosphate turnover on cytoskeletal intermediate filaments.
- Protein phosphatases are essential for maintaining the structural integrity of intermediate filaments and microtubules.
- These findings reveal a critical role for protein phosphatases in dynamic cytoskeletal regulation.