The human collagen beta(1-O)galactosyltransferase, GLT25D1, is a soluble endoplasmic reticulum localized protein

BMC Cell Biology

Research Article

Hans C van Leeuwen¹  Willy JM Spaan¹  Jolanda MP Liefhebber¹  Simone Punt¹ 

[1] Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, 2300 RC Leiden, The Netherlands;

关键词: Endoplasmic Reticulum;    Huh7 Cell;    Mannose Binding Lectin;    Human Hepatoma Cell Line;    Endoplasmic Reticulum Lumen;   

DOI  :  10.1186/1471-2121-11-33

 received in 2009-12-02, accepted in 2010-05-14,  发布年份 2010

来源: Springer

【 摘 要 】

BackgroundGlycosyl transferases transfer glycosyl groups onto their substrate. Localization partially defines their function. Glycosyl transferase 25 domain 1 (GLT25D1) was recently shown to have galactosyltransferase activity towards collagens and another well known substrate, mannose binding lectin (MBL). To gain more insight in the role of galactosylation of lysines in the Gly-X-Lys repeats of collagenous proteins, we investigated the subcellular localization of GLT25D1.ResultsImmunofluorescence analysis of GLT25D1 expressed in the human hepatoma cell line (Huh7), revealed a perinuclear lattice like staining, resembling localization to the endoplasmic reticulum (ER). Possible targeting signals, an N-terminal signal sequence and a C-terminal ER-retention signal, were identified using prediction programs. These signals were then investigated by constructing a series of epitope-tagged forms of GLT25D1 that were analyzed by immunofluorescence and western blotting. In agreement with the predictions our results show that GLT25D1 is directed to the ER lumen as a soluble protein and retained there. Moreover, using two endoglycosidase enzymes EndoH and EndoF, we demonstrate that the putative bi-functional glycosyl transferase itself is a glycoprotein. Additionally we examined co-localization of GLT25D1 with MBL and lysyl hydroxylase 3 (LH3, PLOD3), which is a protein able to catalyze hydroxylation of lysine residues before they can be glycosylated. We demonstrate overlapping localization patterns of GLT25D1, MBL and LH3.ConclusionsTaken together our data indicate that galactosylation of collagenous proteins by the soluble GLT25D1 occurs in the early secretory pathway.

【 授权许可】

Unknown   
© Liefhebber et al; licensee BioMed Central Ltd. 2010. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.