Sequences of the mouse N-acetylglucosaminyltransferase V (Mgat5) mRNA and an mRNA expressed by an Mgat5-deficient cell line

Abnormal galactosylation of immunoglobulin G in cerebrospinal fluid of multiple sclerosis patients

Background:

Glycosylation alterations have been associated with the development of several human diseases and their animal models, including multiple sclerosis.

Objectives:

We aimed to determine whether immunoglobulin G galactosylation might be changed in multiple sclerosis.

Methods:

Immunoglobulin G was isolated from serum and cerebrospinal fluid of patients with multiple sclerosis or viral meningitis and control patients without history of inflammatory or autoimmune disease. A lectin-based assay was used to investigate potential galactosylation modifications of immunoglobulin G.

Results and conclusion:

Galactosylation of immunoglobulin G isolated from cerebrospinal fluid of control patients was found to be age- and gender-dependent. In addition, immunoglobulin G galactosylation was significantly altered in cerebrospinal fluid but not in serum of multiple sclerosis patients. Furthermore, this modification was correlated with an active progression of multiple sclerosis. Finally, the loss of galactosyl moieties was not simply associated with inflammation as no such change was detected in viral meningitis patients characterized by brain inflammation.

Increased expression of N-acetylglucosaminyltransferase-V in human hepatoma cells by retinoic acid and 1alpha,25-dihydroxyvitamin D3

UDP-N-acetylglucosamine: alpha-6-D-mannoside beta-1,6N-acetylglucosaminyltransferase-V activities were determined in human hepatoma cell lines of Hep3B and HepG2, and also compared with those of normal liver tissues and primary hepatocytes. When GlcNAcbeta1-2Manalpha1-3(GlcNAcbeta1-2Manalpha1-4)(Manbeta1-4GlcNAc-2-amino pyridine (GlcN,GlcN-biant-PA) and UDP-GlcNAc were used as substrates, the enzymes displayed optimum temperatures of 50 degrees C, optimum pHs of 6.5 in each case, K(m) values for UDP-GlcNAc to be 5.8 (Hep3B) and 4.5 mM (HepG2) and K(m) values for GlcN,GlcN-biant-PA (mM) to be 1.28 (Hep3B) and 2.4 (HepG2). This indicates that values of Hep3B GlcNAc-transferase-V were distinguishable with HepG2 enzyme. Furthermore, Hep3B enzyme in membrane fraction showed about 1.5-fold higher specific activity (1.423 pmol/(h mg) than that (1.066 pmol/(h mg)) of HepG2. Normal hepatocytes are characterized by very low level of GlcNAc-transferase-V activity whereas hepatoma cells contained high activities. Treatment of hepatoma cells with retinoic acid and 1alpha,2,5-dihydroxyvitamin D(3) (Vit-D(3)) resulted in an increase in GlcNAc-transferase-V activity, while treatment with dimethyl sulfoxide and cytosine-arabinoside resulted in decrease in the enzyme activity. Although retinoic acid (RA) treated cells shows a changed GlcNAc-transferase-V mRNA expression, expression of marker proteins such as alpha-fetoprotein and albumin was not changed. This is the first demonstration of GlcNAc-transferase-V activity in RA and Vit-D(3)-treated hepatoma cell lines.