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Mitotic spindle positioning protein (MISP) preferentially binds to aged F-actin
E Angelo Morales1, Gillian N Fitz1, Matthew J Tyska1
1Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA.
The Journal of Biological Chemistry
|April 8, 2024
Summary
Mitotic spindle positioning protein (MISP) preferentially binds ADP-actin at the pointed ends of filaments, influencing actin bundle formation in microvilli. This nucleotide-sensing mechanism sorts actin bundlers and modulates bundle properties.
Area of Science:
- Cell Biology
- Cytoskeleton Dynamics
- Protein Biochemistry
Background:
- Actin bundling proteins are crucial for cellular structures like microvilli.
- Mitotic spindle positioning protein (MISP) bundles actin filaments, localizing to microvillar rootlets.
- The precise binding mechanism and actin preference of MISP are not fully understood.
Purpose of the Study:
- To investigate MISP's binding preference for specific actin states.
- To determine if MISP binds preferentially to rootlet actin.
- To elucidate the role of nucleotide-bound actin in MISP localization and function.
Main Methods:
- Immunostaining of native intestinal tissue sections.
- Total internal reflection fluorescence microscopy (TIRFm) assays.
- Biochemical assays with purified actin and MISP.
Main Results:
- Microvillar rootlets contain cofilin, indicating high ADP-actin levels.
- Purified MISP shows a binding preference for ADP-actin over ADP-Pi-actin filaments.
- MISP binds to the pointed ends of actively growing actin filaments.
- MISP forms uniform parallel actin bundles in solution.
Conclusions:
- MISP utilizes nucleotide state sensing to bind preferentially to ADP-actin at filament pointed ends.
- This mechanism contributes to the localization of MISP in microvillar rootlets.
- Localized MISP binding may drive parallel bundle formation and regulate mechanical properties in cellular protrusions.
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