Core 2 GlcNAc transferase and kidney tubular cell-specific expression

The expression of glycan chains is precisely regulated in a time- and space-dependent manner. We summarize here our recent work on the kidney tubular cell-specific regulation of core 2 beta-1,6-GlcNAc transferase. Gsl5 gene was first identified by genetic analysis on the basis of polymorphic expression of kidney glycolipids among inbred strains of mice and turned out to be a regulatory gene controlling the level of mRNA of kidney-specific core 2 beta-1,6-GlcNAc transferase. This kidney-specific core 2 GlcNAc transferase takes glycolipids having Gal beta 1-3GalNAc at their termini, Gal beta 1-3GalNAc alpha 1- and beta 1-oligosaccharide derivatives, and glycoproteins having core 1 structure, as substrates. Immunohistochemistry with anti-core 2-Le( x ) monoclonal antibody demonstrated that vesicles located just below the microvillous membrane of proximal tubule cells were clearly stained in a Gsl5 -wild type mouse. Western blotting with the monoclonal antibody detected a major glycoprotein with a molecular mass of 500 kDa in the microsomal fraction of the wild type mouse kidney. In situ hybridization with anti-sense cDNA of kidney-specific core 2 GlcNAc transferase confirmed that Gsl5 gene controls the expression of the core 2 beta-1,6-GlcNAc transferase mRNA in a proximal tubular cell-specific manner. The 5' upstream sequences of the kidney-specific core 2 GlcNAc transferase gene in inbred and wild-derived strains of mice were analyzed, and the phylogenetic analysis of these sequences suggests that functional Gsl5 gene might be produced by the time of subspeciation of M. musculus, about one million years ago.