HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 280, Issue 31, 28370-28381, August 5, 2005

This Article Full Text Full Text (PDF) All Versions of this Article: 280/31/28370    most recent M502469200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ljusberg, J. Articles by Andersson, G. Search for Related Content PubMed PubMed Citation Articles by Ljusberg, J. Articles by Andersson, G. Social Bookmarking                      What's this?

Proteolytic Excision of a Repressive Loop Domain in Tartrate-resistant Acid Phosphatase by Cathepsin K in Osteoclasts^*

Jenny Ljusberg, Yunling Wang, Pernilla Lång, Maria Norgård, Robert Dodds, Kjell Hultenby¶, Barbro Ek-Rylander, and Göran Andersson||

From the Department of Laboratory Medicine, Divisions of Pathology and ^¶Clinical Research Centre, Karolinska Institutet, Karolinska University Hospital, S-141 86 Huddinge, Sweden and Growth Factors Drug Discovery, Johnson and Johnson Pharmaceutical Research and Development, Raritan, New Jersey 08869

Tartrate-resistant acid phosphatase (TRAP) is a metallophosphoesterase participating in osteoclast-mediated bone turnover. Activation of TRAP is associated with the redox state of the di-iron metal center as well as with limited proteolytic cleavage in an exposed loop domain. The cysteine proteinases cathepsin B, L, K, and S as well as the matrix metalloproteinase-2, -9, -13, and -14 are expressed by osteoclasts and/or other bone cells and have been implicated in the turnover of bone and cartilage. To identify proteases that could act as activators of TRAP in bone, we report here that cathepsins K and L, in contrast to the matrix metalloproteinases, efficiently cleaved and activated recombinant TRAP in vitro. Activation of TRAP by cathepsin K/L was because of increases in catalytic activity, substrate affinity, and sensitivity to reductants. Processing by cathepsin K occurred sequentially by an initial excision of the loop peptide Gly¹⁴³–Gly¹⁶⁰ followed by the removal of a Val¹⁶¹–Ala¹⁶² dipeptide at the N terminus of the C-terminal 16-kDa TRAP subunit. Cathepsin L initially released a shorter Gln¹⁵¹–Gly¹⁶⁰ peptide and completed processing at Ser¹⁴⁵ or Gly¹⁴³ at the C terminus of the N-terminal 23-kDa TRAP subunit and at Arg¹⁶³ at the N terminus of the C-terminal 16-kDa TRAP subunit. Mutation of Ser¹⁴⁵ to Ala partly mimicked the effect of proteolysis on catalytic activity, identifying Ser¹⁴⁵ as well as Asp¹⁴⁶ (Funhoff, E. G., Ljusberg, J., Wang, Y., Andersson, G., and Averill, B. A. (2001) Biochemistry 40, 11614–11622) as repressive amino acids of the loop region to maintain the TRAP enzyme in a catalytically latent state. The C-terminal sequence of TRAP isolated from rat bone was consistent with cathepsin K-mediated processing in vivo. Moreover, cathepsin K, but not cathepsin L, co-localized with TRAP in osteoclast-resorptive compartments, supporting a role for cathepsin K in the extracellular processing of monomeric TRAP in the resorption lacuna.

Received for publication, March 7, 2005 , and in revised form, May 27, 2005.

This paper is dedicated to the memory of Dr. Sandy C. Marks, Jr.

^* This work was supported by grants from the Swedish Research Council (to G. A.) and Research Funds from Karolinska Institutet. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

^|| To whom correspondence should be addressed: Dept. of Laboratory Medicine, Division of Pathology, Karolinska Institutet, Karolinska University Hospital, S-141 86 Huddinge, Sweden. Fax: 46-8-585-87730; E-mail: Goran.Andersson{at}labmed.ki.se.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?