Modulation of gelsolin function. Activation at low pH overrides Ca2+ requirement
J A Lamb1, P G Allen, B Y Tuan
1Experimental Medicine Division, Brigham and Women's Hospital, Boston, Massachusetts 02115.
The Journal of Biological Chemistry
|April 25, 1993
Summary
Gelsolin activation, crucial for actin cytoskeleton dynamics, can occur without calcium at low pH. This pH-dependent activation mechanism differs from calcium-mediated pathways, offering insights into cellular processes.
Area of Science:
- Biochemistry
- Cell Biology
- Cytoskeleton Dynamics
Background:
- Gelsolin activation by calcium is linked to actin cytoskeleton reorganization.
- Cytoskeletal changes can occur even with low intracellular calcium levels.
- Previous studies suggested calcium as the primary activator for gelsolin.
Purpose of the Study:
- To investigate gelsolin activation mechanisms beyond calcium.
- To explore the role of pH in gelsolin activity.
- To understand how gelsolin functions under varying calcium and pH conditions.
Main Methods:
- In vitro biochemical assays measuring gelsolin severing and nucleation.
- Fluorescence measurements using Fura-2 to determine calcium requirements.
- Dynamic light scattering to assess changes in gelsolin's molecular shape.
Main Results:
- Gelsolin requires higher calcium concentrations (10 microM) for activation at neutral pH (7.4).
- Calcium requirement for gelsolin decreases at acidic pH, with activation at ~3 microM Ca2+ at pH 6.5.
- At pH below 6.0, gelsolin activates independently of calcium, severing actin and nucleating filaments.
Conclusions:
- Gelsolin exhibits pH-dependent activation, functioning without calcium at acidic pH.
- This pH-mediated activation involves a conformational change in gelsolin.
- Suggests a novel mechanism for gelsolin activation in vivo, independent of calcium transients.
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