Lysosomal cysteine and aspartic proteinases, acid phosphatase, and an endogenous cysteine proteinase inhibitor, cystatin-beta, in rat osteoclasts.
To understand the bone resorption and lysosomal proteinases in osteoclasts, we examined by immunohistochemistry the localization of lysosomal cysteine and aspartic proteinases, acid phosphatase, and cystatin-beta in the rat tibial bone. Immunoreactivity for cathepsins B, C, H, and L, cathepsin D, acid phosphatase, and cystatin-beta was demonstrated in various cells of the bone tissue; in particular, large multinucleated osteoclasts attached to the bone surface and chondroclasts in the proximal growth plate. These cells showed intense immunoreactivity for these lysosomal enzymes and cystatin-beta. Bone surface-lining osteoblasts displayed distinct immunoreactivity for cathepsins B, C, D, H, and acid phosphatase, while osteocytes often exhibited that for cathepsins D, H and acid phosphatase. Chondrocytes in the growth plate demonstrated intense immunoreactivity for cathepsins B, D, and acid phosphatase. Immunoreactivity for cystatin-beta was detected in osteoclasts and chondroclasts only. Large, round multinucleated cells free from the bone surface exhibited weak, faint, or no immunoreactivity for the lysosomal enzymes and cystatin-beta. These results suggest that lysosomal cysteine and aspartic proteinases may play a role in the degradation of organic constituents of the bone matrix. Moreover, cystatin-beta can serve as an excellent marker protein for osteoclasts.
Department of Cell Biology and Neuroanatomy, School of Medicine, Iwate Medical University, Japan.
Y
Y
Ohsawa
T
T
Nitatori
S
S
Higuchi
E
E
Kominami
Y
Y
Uchiyama
D000135:Acid Phosphatase / Q000032:analysis*; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000032:analysis*; D055332:Cystatin M; D015891:Cystatins / Q000032:analysis*; D003546:Cysteine Endopeptidases / Q000032:analysis*; D007150:Immunohistochemistry; D008247:Lysosomes / Q000201:enzymology*; D008297:Male; D010010:Osteoclasts / Q000201:enzymology*; D051381:Rats; D017208:Rats, Wistar
C075076:Cst6 protein, rat; D055332:Cystatin M; D015891:Cystatins; D000135:Acid Phosphatase; D003546:Cysteine Endopeptidases; D016282:Aspartic Acid Endopeptidases