['We showed that the ruffled border lacks a late endosomal lipid, LBPA, but is enriched incholesterol. A hydrophobic amine, U18666A, causes cholesterol accumulation in LBPA+ late endosomes in osteoclasts. Specific targeting of cathepsin K and the vacuolar H+-ATPase at the ruffled border is blocked by U18666A. A membrane trafficking pathway from baso-lateral membrane toward the resorptive organelle is also arrested by the inhibitor. These results indicate cholesterol homeostasis regulates late endosomal/lysosomal trafficking and polarized secretion in resorbing osteoclasts.', 'Protons and acidic proteases are secreted into the resorption lacuna through the ruffled border to solubilize bone mineral and digest the organic bone matrix, respectively. Whereas evidence suggests this event occurs through a vesicular trafficking mechanism, this issue remains unresolved.', 'The distribution of lysobisphosphatidic acid (LBPA) and cholesterol in resorbing osteoclasts was examined by laser scanning confocal microscopy. The effects of U18666A on ruffled border formation were observed by electron microscopy.'] Does pharmacological sequestration of intracellular cholesterol in late endosomes disrupt ruffled border formation in osteoclasts?