Cathepsin K, but not cathepsins B, L, or S, is abundantly expressed in human osteoclasts - PubMed (original) (raw)

. 1996 May 24;271(21):12511-6.

doi: 10.1074/jbc.271.21.12511.

R A Dodds, I E James, J R Connor, C Debouck, S Richardson, E Lee-Rykaczewski, L Coleman, D Rieman, R Barthlow, G Hastings, M Gowen

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Cathepsin K, but not cathepsins B, L, or S, is abundantly expressed in human osteoclasts

F H Drake et al. J Biol Chem. 1996.

Free article

Abstract

Random high throughput sequencing of a human osteoclast cDNA library was employed to identify novel osteoclast-expressed genes. Of the 5475 ESTs obtained, approximately 4% encoded cathepsin K, a novel cysteine protease homologous to cathepsins S and L; ESTs for other cathepsins were rare. In addition, ESTs for cathepsin K were absent or at low frequency in cDNA libraries from numerous other tissues and cells. In situ hybridization in osteoclastoma and osteophyte confirmed that cathepsin K mRNA was highly expressed selecively in osteoclasts; cathepsins S, L, and B were not detectable. Cathepsin K was not detected by in situ hybridization in a panel of other tissues. Western blot of human osteoclastoma or fetal rat humerus demonstrated bands of 38 and 27 kDa, consistent with sizes predicted for pro- and mature cathepsin K. Immunolocalization in osteoclastoma and osteophyte showed intense punctate staining of cathepsin K exclusively in osteoclasts, with a polar distribution that was more intense at the bone surface. The abundant expression of cathepsin K selectively in osteoclasts strongly suggests that it plays a specialized role in bone resorption. Furthermore, the data suggest that random sequencing of ESTs from cDNA libraries is a valuable approach for identifying novel cell-selective genes.

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