IBMS BoneKEy | Perspective

The osteoclast cytoskeleton: How does it work?

Steven L Teitelbaum
Wei Zou

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DOI:10.1138/20110493

Abstract

The capacity of the osteoclast to resorb bone is distinctive, as is the cell's appearance. Both characteristics reflect cytoskeletal organization that yields structures such as the sealing zone and ruffled border. The unique nature of these organelles and their dependence upon contact with bone have been appreciated for some time but insights into the mechanisms by which they are generated come from more recent studies. These insights include the role of integrins, particularly αvβ3, in cytoskeletal organization and the canonical signaling pathway they activate. Investigators now appreciate that the sealing zone isolates the resorptive microenvironment from the general extracellular space, permitting secretion of matrix-degrading molecules on the bone surface. Thus, the osteoclast is a secretory cell that depends upon polarization of exocytic vesicles to the bone-apposed plasma membrane into which they insert under the aegis of vesicle/membrane fusion proteins. This process focally expands and convolutes the plasmalemma included within the sealing zone, eventuating in formation of the ruffled border. Many of these events are now better understood and are the focus of this Perspective.

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