Figure 3.

Formation of the osteoclast ruffled membrane. The unattached osteoclast contains numerous acidified vesicles bearing H⁺ATPases (proton pumps) illustrated as spikes. On attachment to bone, matrix-derived signals polarize the acidified vesicles to the bone-apposed plasma membrane into which they insert under the aegis of Rab3D. Insertion of the vesicles into the plasma membrane greatly increases its complexity and delivers the H⁺ATPases to the resorptive microenvironment.