Related Experiment Videos
Isolation of microvillar microfilaments and associated transmembrane complex from ascites tumor cell microvilli
Abstract:
The association of microvillar microfilaments with the microvillar membrane actin-containing transmembrane complex of MAT-C1 13762 ascites tumor cell microvilli has been investigated by differential centrifugation, gel electrophoresis and electron microscopy of detergent extracts of the isolated microvilli. Several methods have been used to reduce breakdown and solubilization of the microfilament core actin during the detergent extractions for preparation of microvillar core microfilaments. Gel electrophoresis of differential centrifugation fractions demonstrated that over 70% of the total microvillus actin could be pelleted with microfilament cores at 10 000 g under extraction conditions which reduce filament breakdown. Transmission electron microscopy (TEM) of all of the core preparations showed arrays of microfilaments and small microfilament bundles. The major protein components of the microfilament cores, observed by sodium dodecyl sulfate (SDS) electrophoresis, were actin and alpha-actinin. Among the less prominent polypeptide components was a 58 000 Dalton polypeptide (58 K), previously identified as a member of the MAT-Cl transmembrane complex. This three-component complex contains, in addition to 58 K, actin associated directly and stably with a cell surface glycoprotein (Carraway, CAC, Jung, G & Carraway, K L, Proc. natl acad. sci. US 80 (1983) 430). Evidence that the apparent association of complex with the microfilament core was not due simply to co-sedimentation was provided by myosin affinity precipitation. These results provide further evidence that the transmembrane complex is a site for the interaction of microfilaments with the microvillar plasma membrane.
Insights
Researchers investigated how microvillar microfilaments connect to the transmembrane complex in ascites tumor cells. They found that actin and alpha-actinin are key proteins in microfilament cores, interacting with a specific transmembrane complex.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Microvilli are essential cellular projections involved in absorption and cell signaling.
- The actin cytoskeleton, particularly microfilaments, plays a crucial role in maintaining microvillar structure and function.
- Understanding the molecular interactions at the plasma membrane is key to deciphering cellular processes.
Purpose of the Study:
- To investigate the association between microvillar microfilaments and the actin-containing transmembrane complex in MAT-C1 13762 ascites tumor cells.
- To identify the protein components involved in this interaction.
- To elucidate the mechanism by which microfilaments anchor to the microvillar membrane.
Main Methods:
- Differential centrifugation to isolate microfilament cores.
- Gel electrophoresis (SDS-PAGE) to analyze protein composition.
- Transmission electron microscopy (TEM) for structural visualization.
- Myosin affinity precipitation to confirm protein associations.
Main Results:
- Over 70% of microvillus actin was pelleted with microfilament cores under optimized extraction conditions.
- TEM revealed arrays of microfilaments and small bundles in the isolated core preparations.
- Major core proteins identified as actin and alpha-actinin, with a 58,000 Dalton polypeptide (58 K) also present.
- Myosin affinity precipitation provided evidence against simple co-sedimentation, supporting a direct interaction.
Conclusions:
- The study confirms that actin and alpha-actinin are major components of the microvillus core.
- A transmembrane complex, including the 58 K polypeptide, is directly and stably associated with microfilaments.
- These findings strongly suggest that the transmembrane complex serves as an anchoring site for microfilaments within the microvillar plasma membrane.