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Microvillus inclusion disease: a genetic defect affecting apical membrane protein traffic in intestinal epithelium

N A Ameen1, P J Salas

  • 1Department of Pediatrics, Division of Gastroenterology, University of Miami School of Medicine, R-124, P.O. Box 016960, Miami, FL 33173, USA.

Traffic (Copenhagen, Denmark)
|February 24, 2001
PubMed

Insights

Microvillus inclusion disease (MID) shows defects in apical membrane protein trafficking in enterocytes. This suggests MID may be the first identified genetic disorder impacting apical exocytosis.

Area of Science:

  • Cell Biology
  • Gastroenterology
  • Genetics

Background:

  • Microvillus inclusion disease (MID) is characterized by distinctive microvillus inclusions (MIs) in enterocytes.
  • Similarities were noted between MIs in MID and vacuolar apical compartments in cultured epithelial cells.

Observation:

  • Analysis of duodenal biopsies from MID patients revealed a reduced apical F-actin layer thickness and normal microtubules.
  • Immunofluorescence showed decreased apical membrane localization of key proteins like sucrase isomaltase and CFTR in MID enterocytes.
  • These proteins were aberrantly distributed in the apical cytoplasm and MIs, but not at the basolateral membrane.

Findings:

  • MID enterocytes exhibit abnormal distribution of apical membrane proteins, with reduced presence at the apical surface.
  • Four specific apical membrane markers were found within the apical cytoplasm and MIs, indicating a trafficking defect.
  • The basolateral protein Na(+)-K+ATPase showed normal localization, suggesting a specific defect in apical transport.

Implications:

  • These findings support the hypothesis that MID is a genetic disorder affecting apical membrane traffic.
  • MID may represent the first identified genetic defect impacting a late step in apical exocytosis.
  • Understanding this defect could offer new insights into intestinal epithelial cell biology and related disorders.

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