Reduction of  -Gal expression by relocalizing  -galactosidase to the trans-Golgi network and cell surface

• Published in: Glycobiology (Oxford) 2002-11, Vol.12 (11), p.729-739
• Main Authors: Taylor, S. G., Osman, N., McKenzie, I. F.C., Sandrin, M. S.
• Format: Article
• Language: English
• ISSN: 0959-6658; 1460-2423
• DOI: 10.1093/glycob/cwf076

Historically, the most effective means of modifying cell surface carbohydrates has required the intracellular overexpression of glycosyltransferases or glycosidases and is dependent on the enzymes occupying a cellular localization close to the carbohydrate structures they modify. We report on relocalizing the lysosomal resident glycosidase human [alpha]-galactosidase to other regions of the cell, Golgi and cell surface, where it is in closer proximity for cleaving the carbohydrate structure Gal[alpha](1,3)Gal. Relocalization of [alpha]-galactosidase was achieved by using the transmembrane and cytoplasmic domains from the human protein furin, which is known to localize in the trans-Golgi network (TGN) and cell surface. Two chimeric forms of [alpha]-galactosidase were generated, one directing it to the TGN of the cell and the other to the cell surface, as shown by confocal microscopy. The relocalized enzymes have the ability to cleave terminal [alpha]-galactose as detected by expression on the cell surface. Furthermore, when expressed as a transgene in mice, the TGN form of [alpha]-galactosidase was more effective at decreasing cell surface terminal [alpha]-galactose than was the native lysosomal form. When expressed in conjunction with the [alpha]1,2fucosyltransferase that also decreases Gal[alpha](1,3)Gal, the reduction was additive. The ability to relocalize enzymes that modify cell surface carbohydrate structures has far-reaching implications in biology and may be useful in such fields as xenotransplantation and treatment of glycosidase disorders.