Abnormal Rab11-Rab8-vesicles cluster in enterocytes of patients with microvillus inclusion disease.

Vogel GF, Janecke AR, Krainer IM, Gutleben K, Witting B, Mitton SG, Mansour S, Ballauff A, Roland JT, Engevik AC, Cutz E, Müller T, Goldenring JR, Huber LA, Hess MW
Traffic. 2017 18 (7): 453-464

PMID: 28407399 · PMCID: PMC5693299 · DOI:10.1111/tra.12486

Microvillus inclusion disease (MVID) is a congenital enteropathy characterized by accumulation of vesiculo-tubular endomembranes in the subapical cytoplasm of enterocytes, historically termed "secretory granules." However, neither their identity nor pathophysiological significance is well defined. Using immunoelectron microscopy and tomography, we studied biopsies from MVID patients (3× Myosin 5b mutations and 1× Syntaxin3 mutation) and compared them to controls and genome-edited CaCo2 cell models, harboring relevant mutations. Duodenal biopsies from 2 patients with novel Myosin 5b mutations and typical clinical symptoms showed unusual ultrastructural phenotypes: aberrant subapical vesicles and tubules were prominent in the enterocytes, though other histological hallmarks of MVID were almost absent (ectopic intra-/intercellular microvilli, brush border atrophy). We identified these enigmatic vesiculo-tubular organelles as Rab11-Rab8-positive recycling compartments of altered size, shape and location harboring the apical SNARE Syntaxin3, apical transporters sodium-hydrogen exchanger 3 (NHE3) and cystic fibrosis transmembrane conductance regulator. Our data strongly indicate that in MVID disrupted trafficking between cargo vesicles and the apical plasma membrane is the primary cause of a defect of epithelial polarity and subsequent facultative loss of brush border integrity, leading to malabsorption. Furthermore, they support the notion that mislocalization of transporters, such as NHE3 substantially contributes to the reported sodium loss diarrhea.

© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

MeSH Terms (14)

Caco-2 Cells Cell Membrane Enterocytes Humans Malabsorption Syndromes Male Microvilli Mucolipidoses Mutation Myosin Type V Protein Transport Qa-SNARE Proteins rab GTP-Binding Proteins Secretory Vesicles

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