Spatially Distinct Functions of Rho1 during Adherens Junction Maintenance in Remodeling Epithelia

Date of Award

Spring 5-15-2014

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Developmental, Regenerative, & Stem Cell Biology)

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Epithelial maintenance is indispensable for the integrity of tissues, and misregulation can lead to developmentally catastrophic events during gastrulation and adult pathologies such as cancer. In order to understand how to preserve a stable epithelium, it is important to elucidate the molecular mechanisms responsible for maintaining the integrity of formed epithelia. One major feature of epithelia is the presence of multiple junctions that promote intercellular adhesion. Adherens junctions (AJs) in particular are responsible for cell-cell adhesion, through intercellular interactions of E−cadherin. While mechanisms regulating AJ formation have been widely studied, less is known about how AJs are maintained. Previous work from our lab has demonstrated that mutual antagonism between the Rho GTPases Rho1 and Cdc42 is necessary for maintaining AJs in remodeling Drosophila pupal eye epithelia. Conditional loss of Rho1 causes an increase in Cdc42 activity, thereby increasing Drosophila E−cadherin (DE−cadherin) endocytosis, and a resultant defect in AJ maintenance. While Rho GTPases are required for the establishment of AJs through their regulation of actomyosin contractility, what mediates the crosstalk activity of Rho1 and Cdc42 to influence AJ maintenance is unclear. As such, we tested the genetic interaction of Rho1 with a set of genes known to regulate E−cadherin stability at AJs, Rho GTPase activity, and vesicular trafficking and analyzed their ability to rescue the AJ defect in Rho1−depleted pupal eyes. We demonstrated that depletion of selective genes that promote E−cadherin endocytosis restored defective AJs between Rho1−depleted cells, and RhoGDI−mediated crosstalk activity of Rho1 with other Rho GTPases is necessary for AJ remodeling. We also identified other mechanisms underlying the function of Rho1 during AJ maintenance. Rho1 restricts the FERM domain protein Yurt to the basolateral region of epithelial cells and depends on Yurt and Dlg basolateral polarity complex functions to maintain AJs. Rho1 also regulated the recycling of DE−cadherin locally on common recycling endosomes to promote Rok−dependent activation of myosinII and formation of recycling endosomes. This process occurred independent of the ability of Rho1 to regulate actin organization and Cdc42 activity. This work demonstrates multiple ways through which Rho1 influences AJ maintenance in vivo in a spatially restricted manner.

Language

English (en)

Chair and Committee

Gregory Longmore

Committee Members

Thomas Baranski, Jason Mills, Andrey Shaw, James Skeath, Philip Stahl

Comments

Permanent URL: https://doi.org/10.7936/K7XW4GQ9

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