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Mucolipidosis II ‐Related Mutations Inhibit the Exit from the Endoplasmic Reticulum and Proteolytic Cleavage of G lc NA c‐1‐Phosphotransferase Precursor Protein ( GNPTAB )
Author(s) -
Pace Raffaella,
Coutinho Maria Francisca,
KochNolte Friedrich,
Haag Friedrich,
Prata Maria João,
Alves Sandra,
Braulke Thomas,
Pohl Sandra
Publication year - 2014
Publication title -
human mutation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 162
eISSN - 1098-1004
pISSN - 1059-7794
DOI - 10.1002/humu.22502
Subject(s) - frameshift mutation , biology , missense mutation , endoplasmic reticulum , microbiology and biotechnology , protein subunit , mutant protein , mucolipidosis , g alpha subunit , phenotype , mutation , gene , biochemistry , enzyme
Mucolipidosis ( ML ) II and ML III alpha/beta are two pediatric lysosomal storage disorders caused by mutations in the GNPTAB gene, which encodes an α/β‐subunit precursor protein of GlcNAc‐1‐phosphotransferase. Considerable variations in the onset and severity of the clinical phenotype in these diseases are observed. We report here on expression studies of two missense mutations c.242G>T (p.Trp81Leu) and c.2956C>T (p.Arg986Cys) and two frameshift mutations c.3503_3504delTC (p.Leu1168Gln fs X5) and c.3145insC (p.Gly1049Arg fs X16) present in severely affected MLII patients, as well as two missense mutations c.1196C>T (p.Ser399Phe) and c.3707A>T (p.Lys1236Met) reported in more mild affected individuals. We generated a novel α‐subunit‐specific monoclonal antibody, allowing the analysis of the expression, subcellular localization, and proteolytic activation of wild‐type and mutant α/β‐subunit precursor proteins by W estern blotting and immunofluorescence microscopy. In general, we found that both missense and frameshift mutations that are associated with a severe clinical phenotype cause retention of the encoded protein in the endoplasmic reticulum and failure to cleave the α/β‐subunit precursor protein are associated with a severe clinical phenotype with the exception of p.Ser399Phe found in ML III alpha/beta. Our data provide new insights into structural requirements for localization and activity of G lc NA c‐1‐phosphotransferase that may help to explain the clinical phenotype of ML II patients.