Elijah Marquez
BioE Ph.D. Defense Presentation
June 26, 2024
3:30PM
IBB Suddath Seminar Room 1128
Zoom link: https://gatech.zoom.us/j/96421964446
Thesis Advisor
Andrés J. García, Ph.D., George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology
Thesis Committee Members
Dr. Cheng Zhu, Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology
Dr. John Blazeck, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology
Dr. Wilbur Lam, Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology
Dr. Jianping Fu, Department of Mechanical Engineering, University of Michigan
Mechanotransduction at Focal Adhesions: Interplay among Force, FAK, and YAP:
The body experiences a variety of mechanical cues in day-to-day function: compressive and tensile stresses in bone and cartilage to latent mechanical signals from the extracellular matrix (ECM). Mechanical cues drive processes such as cell migration and proliferation. Cells sense mechanical signals via cell-ECM interactions, which are primarily facilitated through focal adhesions (FAs). FAs have 100s of unique components: a few key proteins are vinculin, talin, and focal adhesion kinase (FAK). While FA turnover has been well recognized, how cells translate mechanical signals at FAs into biochemical changes is less understood. Previous work demonstrated that yes-associated protein (YAP), a transcriptional coactivator, responds to changes in adhesive area and substrate rigidity. Deleting essential FA proteins alters YAP activity, and YAP upregulates FA-related genes. Our objective is to further our understanding of cell adhesion by elucidating how cells utilize focal adhesions to translate mechanical cues into biochemical signals. I hypothesize that FAs utilize interactions between vinculin, talin, and FAK and spatially and temporally coordinate FA turnover rates and forces to induce YAP activity. Therefore, as I alter vinculin-talin-FAK interactions, I expect a reduction in YAP activity. As I spatially direct cells to form more focal adhesions across the cell periphery and major axis, I expect to induce an increase in YAP activity. In this thesis, I demonstrated that reducing micropillar area while keeping array stiffness constant, which increases force map resolution, alters cell behavior by reducing cell contractility and spread area. I evaluated the impact of removing talin-FAK and talin-vinculin interactions on YAP activity. Upon removing vinculin, FAK, or talin; impairing FAK or vinculin’s functionality, or abrogating talin-FAK or talin-vinculin interactions, there was a drop in YAP’s nuclear accumulation and transcriptional activity. Lastly, I developed a platform for spatially and temporally directing FAs to monitor FA distribution, number, and cell generated traction forces. This work advances our understanding of mechanotransduction by dissecting the relationship between FAs and YAP, which aids in rationally designing biomaterial therapies for modulating YAP expression to treat cancer and fibrosis.