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Calmodulin concentrated at the osteoclast ruffled border modulates acid secretion
W Radding1, J P Williams, R W Hardy
1Department of Pathology, University of Alabama at Birmingham 35294.
Journal of Cellular Physiology
|July 1, 1994
Summary
Calmodulin, a calcium-binding protein, is crucial for osteoclast function. Its concentration and location change during bone attachment, and it regulates acid secretion essential for bone resorption.
Area of Science:
- Cell Biology
- Biochemistry
- Skeletal Biology
Background:
- Osteoclasts are vital for bone remodeling and calcium homeostasis.
- High extracellular calcium during bone resorption impacts osteoclast signaling.
- Calmodulin is a key calcium-binding regulatory protein.
Purpose of the Study:
- To investigate the role of calmodulin in osteoclast regulation.
- To determine if calmodulin is affected by the high calcium environment of bone resorption.
- To explore calmodulin's involvement in osteoclastic acid secretion.
Main Methods:
- Using calmodulin antagonists (trifluoperazine, calmidazolium) to inhibit osteoclast activity.
- Employing quantitative immunofluorescence and Western blotting to measure calmodulin levels.
- Utilizing scanning confocal microscopy and electron microscopy for calmodulin localization.
- Assessing ATP-dependent acid transport in osteoclast membrane vesicles.
Main Results:
- Calmodulin antagonists significantly inhibited avian osteoclast bone resorption.
- Calmodulin concentration increased severalfold in bone-attached osteoclasts.
- Calmodulin localized to areas of bone attachment and the ruffled membrane.
- Calmodulin antagonist inhibited vesicle acid transport, an effect reversed by excess calmodulin.
Conclusions:
- Osteoclast calmodulin concentration and distribution are modulated by bone attachment.
- Calmodulin plays a critical role in regulating osteoclastic acid secretion.
- Calmodulin is a key mediator of osteoclast function in bone resorption.