RRC ID 41364
Author Ishibashi O, Inui T, Mori Y, Kurokawa T, Kokubo T, Kumegawa M.
Title Quantification of the expression levels of lysosomal cysteine proteinases in purified human osteoclastic cells by competitive RT-PCR.
Journal Calcif Tissue Int
Abstract Cathepsin K is a lysosomal cysteine proteinase (LCP) predominantly expressed in osteoclasts. This study was conducted to evaluate the importance of human cathepsin K for osteoclastic bone resorption relative to that of other LCPs. To accomplish this, we quantitatively determined the expression levels of major LCPs (cathepsins B, K, L, and S) in human osteoclastic cells by using competitive RT-PCR. Giant cell tumor of bone (GCT) was used as a source of human osteoclastic cells, since the tissue was shown to contain a large number of cells satisfying the criteria for typical osteoclasts. The involvement of LCPs in the bone-resorption process by the GCT cells was confirmed by showing that trans-epoxysucciny-L-leucylamido-(4-guanidino) butane (E-64), a nonselective cysteine proteinase inhibitor, exerted an inhibitory effect on the pit formation. We isolated osteoclast-like cells (OLCs) positive for tartrate-resistant acid phosphatase (TRAP) and cathepsin K from the GCT tissue to a degree of almost 95% purity. In these cells, the expression of cathepsin K was shown to be approximately 20-, 130-, and 410-fold stronger than that of cathepsins B, L, and S, respectively. A similar result was obtained when human bone marrow cells in culture were used as another source of OLCs. Further, we found that cathepsin K was expressed in OLCs far more strongly than in several human nonosteoclastic cells including osteoblastic cell lines. The abundant and selective expression of cathepsin K in OLCs relative to that of other LCPs suggests that cathepsin K is mainly responsible for osteoclastic degradation of human bone matrix.
Volume 68(2)
Pages 109-16
Published 2001-2-1
DOI 10.1007/BF02678149
PMID 11310346
MeSH Acid Phosphatase / metabolism Adult Bone Marrow Cells / drug effects Bone Marrow Cells / enzymology Bone Resorption / enzymology Bone Resorption / prevention & control Calcitonin / pharmacology Cathepsin K Cathepsins / antagonists & inhibitors Cathepsins / biosynthesis Cathepsins / genetics* Cysteine Endopeptidases / biosynthesis Cysteine Endopeptidases / genetics* DNA Primers / chemistry Dose-Response Relationship, Drug Female Fluorescent Antibody Technique, Indirect Gene Expression Giant Cell Tumor of Bone Glyceraldehyde-3-Phosphate Dehydrogenases / biosynthesis Glyceraldehyde-3-Phosphate Dehydrogenases / genetics Humans Isoenzymes / metabolism Leucine / analogs & derivatives* Leucine / pharmacology Osteoblasts / enzymology Osteoclasts / drug effects Osteoclasts / enzymology* RNA, Messenger / biosynthesis Reverse Transcriptase Polymerase Chain Reaction Tartrate-Resistant Acid Phosphatase Tumor Cells, Cultured
IF 3.423
Times Cited 17
Human and Animal Cells