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The RabGAPs EPI64A and EPI64B regulate the apical structure of epithelial cells †
Matthew R Miller1, David J McDermitt1, Cecile Sauvanet1
1Weill Institute for Cell and Molecular Biology, Department of Molecular Biology and Genetics, Cornell University, Ithaca NY 14850.
EPI64A and EPI64B proteins organize the apical surface of epithelial cells. Their disruption affects microvilli and cell junctions, highlighting their role in apical domain morphology.
Area of Science:
- Cell Biology
- Epithelial Cell Biology
- Molecular Cell Biology
Background:
- Epithelial cells possess specialized apical structures like microvilli and junctions.
- TBC/RabGAP proteins regulate cellular processes, including membrane trafficking and cytoskeletal organization.
Purpose of the Study:
- To investigate the function of TBC/RabGAPs EPI64A and EPI64B in organizing the apical aspect of epithelial cells.
- To determine the specific roles of EPI64A and EPI64B in microvilli formation, apical junction integrity, and overall epithelial cell morphology.
Main Methods:
- Utilized CRISPR/Cas9 gene editing to create knockout cell lines (Jeg-3 and Caco2) lacking EPI64A, EPI64B, or both.
- Investigated protein interactions, specifically EPI64A binding to EBP50/NHERF1 and active ezrin.
- Analyzed the localization of EPI64A and EPI64B to microvilli and their impact on apical structures using microscopy and cellular morphology assessments.
Main Results:
- Loss of EPI64B in Jeg-3 cells reduced apical microvilli, with a further decrease in double knockouts, linked to Rab8 and Rab35 misregulation.
- Epithelial cells lacking EPI64A showed partial apical junction disruption, exacerbated in double knockouts.
- Caco2 cells lacking EPI64B exhibited wavy junctions, while double knockouts displayed severe apical morphology changes, including stellate shapes.
Conclusions:
- EPI64A and EPI64B are crucial regulators of the apical domain in polarized epithelial cells.
- These proteins specifically influence microvilli structure and apical junction stability.
- The distinct and overlapping functions of EPI64A and EPI64B highlight their coordinated role in maintaining epithelial apical organization.
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