Cell-mediated extracellular acidification and bone resorption: evidence for a low pH in resorbing lacunae and localization of a 100-kD lysosomal membrane protein at the osteoclast ruffled border.

Abstract

The extracellular compartment where bone resorption occurs, between the osteoclast and bone matrix, is shown in this report to be actively acidified. The weak base acridine orange accumulates within this compartment but dissipates after incubation with ammonium chloride. Upon removal of ammonium chloride, the cells are able to rapidly reacidify this compartment. The highly convoluted plasma membrane of the osteoclast facing this acidic compartment (ruffled border) is shown to contain a 100-kD integral membrane protein otherwise present in limiting membranes of lysosomes and other related acidified organelles

Cytoplasmic Terminus of Vacuolar Type Proton Pump Accessory Subunit Ac45 Is Required for Proper Interaction with V0 Domain Subunits and Efficient Osteoclastic Bone Resorption

“…Generation of a continuous proton gradient across the osteoclastic ruffled border domain is critical to its resorptive function (2,5). Previous studies have shown that various V-ATPase subunits play important roles in osteoclast differentiation and function (9, 24, 39).…”

“…The ruffled border is the "resorptive organelle" of the osteoclast and is formed by the polarized targeting and fusion of acidified intracellular vesicles with the plasma membrane (2)(3)(4). These transport vesicles courier acidifying machineries as well as osteolytic enzymes such as, TRACP, cathepsin K, and matrix metalloproteinases (2,(5)(6)(7) to the ruffled border membrane domain where each cargo plays a discrete role in the resorptive function. Vacuolar H ϩ -adenosine triphosphatases (V-ATPases) 5 that line the ruffled border have long been established to play a vital role in the resorptive process.…”

“…These transport vesicles courier acidifying machineries as well as osteolytic enzymes such as, TRACP, cathepsin K, and matrix metalloproteinases (2,(5)(6)(7) to the ruffled border membrane domain where each cargo plays a discrete role in the resorptive function. Vacuolar H ϩ -adenosine triphosphatases (V-ATPases) 5 that line the ruffled border have long been established to play a vital role in the resorptive process. V-ATPases function to pump H ϩ into the underlying resorptive lacunae.…”

Expression of 16 kDa proteolipid of vacuolar-type H(+)-ATPase in human pancreatic cancer

“…V-ATPase has been purified from endomembrane systems including lysosomes, chromaffin granules, endosomes, synaptic vesicles and clathrin-coated vesicles (Mellman et al, 1986;Arai et al, 1987a;Nelson, 1989;Moriyama and Nelson, 1989;Futai, 1990, Arai et al, 1993). In addition, V-ATPase also has been detected in the plasma membrane of a few specalised cell types including osteoclasts (Baron et al, 1985;Akisaka and Gay, 1986;Vaananen et al, 1990), macrophages (Swallow et al, 1990;Bidani and Brown, 1992;Tapper and Sundler, 1992), activated neutrophils (Nanda et al, 1992), renal intercalated cells (Verlander et al, 1991) and some tumour cell lines (Martinez-Zaguilan et al, 1991).…”

Morphological, Biochemical and Molecular Biology Approaches for the Diagnosis of Lysosomal Storage Diseases

“…44 In addition, while in most cell types expression of lysosomal hydrolases is intralysosomal, in osteoclasts, the lysosomal hydrolases are expressed at the ruffled border. 13,86,105 This results in the unique manifestation of skeletal lesions seen in several lysosomal storage diseases.…”