Date of Award

Spring 5-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical Engineering

Committee Director

Venkat Maruthamuthu

Committee Member

Sharan Asundi

Committee Member

Stacie Ringleb

Committee Member

Guijun Wang

Abstract

E-cadherin is the chief mediator of cell-cell adhesion between epithelial cells and is a known mechanosensor. Force transmission and stiffness sensing are two crucial aspects of E-cadherin mechanobiology.

E-cadherin has an extracellular adhesive region, a transmembrane region and an intracellular region that binds to adhesion-associated proteins. Here, we assessed how different factors affect the level of force transmission (i) from inside the cell such as adhesion-associated proteins, (ii) on the cell membrane, such as growth factor receptors and (iii) outside the cell, such as different binding partners in adhesion. To study the level of force transmission inside the cell, we studied the role of vinculin and α-catenin in transmitting endogenous forces at cell-cell contacts. We found that vinculin, not α-catenin, is pivotal for transmitting high endogenous forces at cell-cell contacts through E-cadherin. To study how the level of force transmission is affected by factors on the cell membrane, we investigated the effect of EGFR on the intercellular forces transmitted at cell-cell contacts. We found that EGFR activity significantly affects the level of intercellular forces. In order to understand how the level of force transmission depends on binding partners from outside the cell, we studied homophilic and heterophilic interactions of cadherins. We found that the intercellular tension for the heterophilic E-cad/N-cad interaction is higher than the homophilic E-cad/E-cad interaction. Additionally, we also devised a modified traction force microscopy method using a novel, simple strategy for coincident immunofluorescence and traction force microscopy.

Moreover, E-cadherin adhesions reside in a microenvironment that is comprised of adjacent epithelial cells. We found that E-cadherin adhesions change their organization depending on the magnitude of the epithelial cell-like elasticity of their microenvironment. Such E-cadherin adhesions were of two types: linear shaped adhesions and irregularly shaped adhesions. We found that linear adhesions were dependent on formin-dependent linear actin bundles and irregular adhesions were dependent on high local actin density. Thus, we found that actin is a crucial determinant of how E-cadherin adhesions are organized in response to cell-like soft microenvironments. All these findings have important implications for tissue development (morphogenesis), dysregulation (such as during cancer progression) as well as tissue engineering.

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DOI

10.25777/yxrf-jt17

ISBN

9798379734732

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