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Altered folding, turnover, and polarized sorting act in concert to define a novel pathomechanism of congenital sucrase-isomaltase deficiency.

Abstract

Naturally occurring mutants of membrane and secretory proteins are often associated with the pathogenesis of human diseases. Here, we describe the molecular basis of a novel phenotype of congenital sucrase-isomaltase deficiency (CSID), a disaccharide malabsorption disorder of the human intestine in which several structural features and functional capacities of the brush-border enzyme complex sucrase-isomaltase (SI) are affected. The cDNA encoding SI from a patient with CSID reveals a mutation in the isomaltase subunit of SI that results in the substitution of a cysteine by an arginine at amino acid residue 635 (C635R). When this mutation is introduced into the wild type cDNA of SI a mutant enzyme, SI(C635R), is generated that shows a predominant localization in the endoplasmic reticulum. Nevertheless, a definite localization of SI(C635R) in the Golgi apparatus and at the cell surface could be also observed. Epitope mapping with conformation-specific mAbs protease sensitivity assays, and enzymatic activity measurements demonstrate an altered folding pattern of SI(C635R) that is responsible for a substantially increased turnover rate and an aberrant sorting profile. Thus, SI(C635R) becomes distributed also at the basolateral membrane in contrast to wild type SI. Concomitant with the altered sorting pattern, the partial detergent extractability of wild type SI shifts to a complete detergent solubility with Triton X-100. The mutation has therefore affected an epitope responsible for the apical targeting fidelity of SI. Altogether, the combined effects of the C635R mutation on the turnover rate, function, polarized sorting, and detergent solubility of SI constitute a unique and novel pathomechanism of CSID.

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  • Authors+Show Affiliations

    ,

    Department of Physiological Chemistry, University of Veterinary Medicine Hannover, D-30559 Hannover, Germany.

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    Source

    The Journal of biological chemistry 281:20 2006 May 19 pg 14393-9

    MeSH

    Adult
    Amino Acid Sequence
    Animals
    Carbohydrate Metabolism, Inborn Errors
    Detergents
    Endoplasmic Reticulum
    Epitope Mapping
    Humans
    Intestines
    Male
    Molecular Sequence Data
    Octoxynol
    Protein Folding
    Sequence Homology, Amino Acid
    Sucrase-Isomaltase Complex

    Pub Type(s)

    Journal Article
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    16543230

    Citation

    Keiser, Markus, et al. "Altered Folding, Turnover, and Polarized Sorting Act in Concert to Define a Novel Pathomechanism of Congenital Sucrase-isomaltase Deficiency." The Journal of Biological Chemistry, vol. 281, no. 20, 2006, pp. 14393-9.
    Keiser M, Alfalah M, Pröpsting MJ, et al. Altered folding, turnover, and polarized sorting act in concert to define a novel pathomechanism of congenital sucrase-isomaltase deficiency. J Biol Chem. 2006;281(20):14393-9.
    Keiser, M., Alfalah, M., Pröpsting, M. J., Castelletti, D., & Naim, H. Y. (2006). Altered folding, turnover, and polarized sorting act in concert to define a novel pathomechanism of congenital sucrase-isomaltase deficiency. The Journal of Biological Chemistry, 281(20), pp. 14393-9.
    Keiser M, et al. Altered Folding, Turnover, and Polarized Sorting Act in Concert to Define a Novel Pathomechanism of Congenital Sucrase-isomaltase Deficiency. J Biol Chem. 2006 May 19;281(20):14393-9. PubMed PMID: 16543230.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Altered folding, turnover, and polarized sorting act in concert to define a novel pathomechanism of congenital sucrase-isomaltase deficiency. AU - Keiser,Markus, AU - Alfalah,Marwan, AU - Pröpsting,Marcus J, AU - Castelletti,Deborah, AU - Naim,Hassan Y, Y1 - 2006/03/16/ PY - 2006/3/18/pubmed PY - 2006/7/22/medline PY - 2006/3/18/entrez SP - 14393 EP - 9 JF - The Journal of biological chemistry JO - J. Biol. Chem. VL - 281 IS - 20 N2 - Naturally occurring mutants of membrane and secretory proteins are often associated with the pathogenesis of human diseases. Here, we describe the molecular basis of a novel phenotype of congenital sucrase-isomaltase deficiency (CSID), a disaccharide malabsorption disorder of the human intestine in which several structural features and functional capacities of the brush-border enzyme complex sucrase-isomaltase (SI) are affected. The cDNA encoding SI from a patient with CSID reveals a mutation in the isomaltase subunit of SI that results in the substitution of a cysteine by an arginine at amino acid residue 635 (C635R). When this mutation is introduced into the wild type cDNA of SI a mutant enzyme, SI(C635R), is generated that shows a predominant localization in the endoplasmic reticulum. Nevertheless, a definite localization of SI(C635R) in the Golgi apparatus and at the cell surface could be also observed. Epitope mapping with conformation-specific mAbs protease sensitivity assays, and enzymatic activity measurements demonstrate an altered folding pattern of SI(C635R) that is responsible for a substantially increased turnover rate and an aberrant sorting profile. Thus, SI(C635R) becomes distributed also at the basolateral membrane in contrast to wild type SI. Concomitant with the altered sorting pattern, the partial detergent extractability of wild type SI shifts to a complete detergent solubility with Triton X-100. The mutation has therefore affected an epitope responsible for the apical targeting fidelity of SI. Altogether, the combined effects of the C635R mutation on the turnover rate, function, polarized sorting, and detergent solubility of SI constitute a unique and novel pathomechanism of CSID. SN - 0021-9258 UR - https://wwww.unboundmedicine.com/medline/citation/16543230/Altered_folding_turnover_and_polarized_sorting_act_in_concert_to_define_a_novel_pathomechanism_of_congenital_sucrase_isomaltase_deficiency_ L2 - http://www.jbc.org/cgi/pmidlookup?view=long&pmid=16543230 DB - PRIME DP - Unbound Medicine ER -