Recruitment of Polarity Complexes and Tight Junction Proteins to the Site of Apical Bulk Endocytosis

Amy C. Engevik, Evan S. Krystofiak, Izumi Kaji, Anne R. Meyer, Victoria G. Weis, Anna Goldstein, Alexander W. Coutts, Tamene Melkamu, Milena Saqui-Salces, James R. Goldenring

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Background & Aims: The molecular motor, Myosin Vb (MYO5B), is well documented for its role in trafficking cargo to the apical membrane of epithelial cells. Despite its involvement in regulating apical proteins, the role of MYO5B in cell polarity is less clear. Inactivating mutations in MYO5B result in microvillus inclusion disease (MVID), a disorder characterized by loss of key apical transporters and the presence of intracellular inclusions in enterocytes. We previously identified that inclusions in Myo5b knockout (KO) mice form from invagination of the apical brush border via apical bulk endocytosis. Herein, we sought to elucidate the role of polarity complexes and tight junction proteins during the formation of inclusions. Methods: Intestinal tissue from neonatal control and Myo5b KO littermates was analyzed by immunofluorescence to determine the localization of polarity complexes and tight junction proteins. Results: Proteins that make up the apical polarity complexes—Crumbs3 and Pars complexes—were associated with inclusions in Myo5b KO mice. In addition, tight junction proteins were observed to be concentrated over inclusions that were present at the apical membrane of Myo5b-deficient enterocytes in vivo and in vitro. Our mouse findings are complemented by immunostaining in a large animal swine model of MVID genetically engineered to express a human MVID-associated mutation that shows an accumulation of Claudin-2 over forming inclusions. The findings from our swine model of MVID suggest that a similar mechanism of tight junction accumulation occurs in patients with MVID. Conclusions: These data show that apical bulk endocytosis involves the altered localization of apical polarity proteins and tight junction proteins after loss of Myo5b.

Original languageEnglish (US)
Pages (from-to)59-80
Number of pages22
JournalCellular and Molecular Gastroenterology and Hepatology
Issue number1
StatePublished - Jan 1 2021

Bibliographical note

Funding Information:
Funding This study was supported by National Institutes of Health grants K01 DK121869 (A.C.E.); R01 DK48370, R01 DK70856, RC2 DK118640 (J.R.G.); and R43 DK109820 (T.M.). Supported by a gift from the Christine Volpe Fund (J.R.G.). This work also was supported by core resources of the Vanderbilt Digestive Disease Center (P30 DK058404), the Vanderbilt-Ingram Cancer Center ( P30 CA68485 ), VU Cell Imaging Shared Resource, and the VUMC Digital Histology Shared Resource (supported by a VA Shared Equipment Grant 1IS1BX003097).

Publisher Copyright:
© 2021 The Authors


  • Apical Bulk Endocytosis
  • Cortactin
  • Inclusions
  • Microvillus Inclusion Disease (MVID)
  • Myosin Vb
  • Occludin
  • Polarity
  • Tight Junctions
  • Trafficking
  • ZO-1

PubMed: MeSH publication types

  • Journal Article
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't


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