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J. Biol. Chem., Vol. 282, Issue 8, 5195-5200, February 23, 2007

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Biosynthesis of Chondroitin and Heparan Sulfate in Chinese Hamster Ovary Cells Depends on Xylosyltransferase II^*

From the Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation and Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104

Xylosyltransferase (XylT) catalyzes the initial enzymatic reaction in the glycosaminoglycan assembly pathway for proteoglycan biosynthesis. Its activity is thought to be rate-limiting. Two xylosyltransferases have been found using genomic analyses, and one of these, XylT1, has been shown to have xylosyltransferase activity. On the other hand, the less studied XylT2 in recombinant form lacks xylosyltransferase activity and has no known function. Wild-type Chinese hamster ovary cells express abundant Xylt2 mRNA levels and lack detectable Xylt1 mRNA levels. Analysis of a previously described Chinese hamster ovary cell xylosyltransferase mutant (psgA-745) shows that it harbors an Xylt2 nonsense mutation and fails to assemble glycosaminoglycans onto recombinant biglycan. Transfection of this cell line with a murine Xylt2 minigene results in the production of recombinant chondroitin sulfate-modified biglycan core protein and restoration of fibroblast growth factor binding to cell surface-associated heparan sulfate. Expression analyses on 10 different human transformed cell lines detect exclusive XYLT2 expression in two and co-expression of XYLT1 and XYLT2 in the others but at disparate ratios where XYLT2 expression is greater than XYLT1 in most cell lines. These results indicate that XylT2 has a significant role in proteoglycan biosynthesis and that cell type may control which family member is utilized.

Received for publication, October 16, 2006 , and in revised form, December 18, 2006.

^* This work was supported by American Heart Association Grant 0265270Z and National Institutes of Health Grant P20 RR018758. 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.

The on-line version of this article (available at http://www.jbc.org) contains a supplemental figure and a supplemental table.

¹ Present address: Integrative Biology Graduate Program, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park Rd., Dallas, TX 75390.

² To whom correspondence should be addressed: Cardiovascular Biology Research Program, 825 NE 13th St. MS#45, Oklahoma City, OK 73104. Tel.: 405-271-7073; Fax: 405-271-7417; E-mail: Myron-Hinsdale{at}omrf.ouhsc.edu.

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