O-Fucosylation of ADAMTSL2 is required for secretion and is impacted by geleophysic dysplasia-causing mutations [Molecular Bases of Disease]

ADAMTSL2 mutations cause an autosomal recessive connective tissue disorder, geleophysic dysplasia 1 (GPHYSD1), which is characterized by short stature, small hands and feet, and cardiac defects. ADAMTSL2 is a matricellular protein previously shown to interact with latent transforming growth factor-β binding protein 1 and influence assembly of fibrillin 1 microfibrils. ADAMTSL2 contains seven thrombospondin type-1 repeats (TSRs), six of which contain the consensus sequence for O-fucosylation by protein O-fucosyltransferase 2 (POFUT2). O-fucose–modified TSRs are subsequently elongated to a glucose β1-3-fucose (GlcFuc) disaccharide by β1,3-glucosyltransferase (B3GLCT). B3GLCT mutations cause Peters Plus Syndrome (PTRPLS), which is characterized by skeletal defects similar to GPHYSD1. Several ADAMTSL2 TSRs also have consensus sequences for C-mannosylation. Six reported GPHYSD1 mutations occur within the TSRs and two lie near O-fucosylation sites. To investigate the effects of TSR glycosylation on ADAMTSL2 function, we used MS to identify glycan modifications at predicted consensus sequences on mouse ADAMTSL2. We found that most TSRs were modified with the GlcFuc disaccharide at high stoichiometry at O-fucosylation sites and variable mannose stoichiometry at C-mannosylation sites. Loss of ADAMTSL2 secretion in POFUT2−/− but not in B3GLCT−/− cells suggested that impaired ADAMTSL2 secretion is not responsible for skeletal defects in PTRPLS patients. In contrast, secreti...

Source: Journal of Biological Chemistry - November 13, 2020 Category: Chemistry Authors: Ao Zhang, Steven J. Berardinelli, Christina Leonhard-Melief, Deepika Vasudevan, Ta-Wei Liu, Andrew Taibi, Sharee Giannone, Suneel S. Apte, Bernadette C. Holdener, Robert S. Haltiwanger Tags: Glycobiology and Extracellular Matrices Source Type: research