Biochemical correlation of activity of the alpha-dystroglycan-modifying glycosyltransferase POMGnT1 with mutations in Muscle-Eye-Brain disease

Josef Voglmeir , Sara Kaloo , Nicolas Laurent , Marco M Meloni , Lisa Bohlmann , Iain B. H. Wilson , Sabine Flitsch (1)

1 Manchester Interdisciplinary Biocentre (MIB), Room 3.020

Congenital muscular dystrophies have a broad spectrum of genotypes and phenotypes and there is a need for a better biochemical understanding of this group of diseases in order to aid diagnosis and treatment. Several mutations resulting in these diseases cause reduced O-mannosyl glycosylation of glycoproteins, including alpha-dystroglycan. The enzyme protein-O-mannose N-acetylglucosaminyltransferase 1 (POMGnT1; EC 2.4.1.-) catalyzes the transfer of N-acetylglucosamine to O-linked mannose of a-dystroglycan, and affect glycosyltransferases or glycosyltransferase-like genes. Here we describe the biochemical characterization of 14 clinical mutants of the glycosyltransferase POMGnT1, which have been linked to Muscle-Eye-Brain disease or similar conditions. Truncated mutant variants of the human enzyme (rPOMGnT1) were expressed in Escherichia coli and screened for catalytic activity. We find that three mutants show some activity towards mannosylated peptide substrates mimicking alpha-dystroglycan; the residues affected by these mutants are predicted by homology modeling to be on the periphery of the POMGnT1 surface. Only in part does the published location of a mutated residue on the periphery of the protein structure correlate with a less severe disease mutant.

Mots clés: Life Sciences

Josef Voglmeir, Sara Kaloo, Nicolas Laurent, Marco M Meloni, Lisa Bohlmann, et al.. Biochemical correlation of activity of the alpha-dystroglycan-modifying glycosyltransferase POMGnT1 with mutations in Muscle-Eye-Brain disease. Biochemical Journal, 2011, 436 (2), pp.447-455. ⟨10.1042/BJ20101059⟩. ⟨hal-00592577⟩