Graduation Year

2026

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Molecular Biosciences

Major Professor

Dr. Lindsey Shaw, Ph.D.

Committee Member

Dr. Stanley Stevens, Ph.D.

Committee Member

Dr. Wenqi Yu, Ph.D.

Committee Member

Dr. Xingmin Sun, Ph.D.

Keywords

Degradomics, N-terminomics, V8 protease, Pathodegradome, Host-response

Abstract

Staphylococcus aureus deploys an arsenal of virulence effectors to remodel the host environment during infection, while simultaneously the host mounts an immune response to contain and eliminate this bacterium. This dynamic interplay defines the host-pathogen interface and shapes infection outcome. In this context, the secreted proteases represent a major arm of S. aureus pathogenesis, promoting bacterial persistence in the host by dismantling immune defenses, cleaving host signaling molecules and reshaping the host proteome. However, traditional substrate-by-substrate characterization cannot reveal the full scope of proteolytic activity occurring during infection. To address this, we developed Terminal Amine-Guanidination of Substrates-Charge Reversal (TAGS-CR), a high-throughput N-terminomic methodology that streamlines protease substrate capture at a resolution that has not been previously achieved. We applied TAGS-CR to define the V8 protease pathodegradome in human neutrophils and human lung tissue. In neutrophils, V8 targeted multiple levels of host antibacterial functionality, including leukocyte extravasation, integrin interactions, degranulation, phagocytosis, ROS production and apoptosis. In lung tissue, V8 continued to target neutrophil mediated defenses, however this study also revealed new dimensions of protease activity, including epithelial barrier disruption and modulation of iron homeostasis and inflammation. Together, these studies provide unparallelled insight into protease activity in the context of host-pathogen interplay, with direct implications for clinical advancements such as protease inhibitor design, host-directed therapies and pathodegradome based diagnostics. Moving beyond the proteases, we investigated the host side of host-pathogen interaction. Within the globally dominant CC5-MRSA lineage, the hypervirulent offshoot ST3390 has recently emerged in Tampa Bay, diverging from the well characterized ST5. Here we used a genetically diverse mouse model challenged with each strain in a model of bacteremia to investigate the determinants of disease outcome. At the pathogen level, we identified strain specific proteomic signatures, with an antibody suppression identified as a defining feature of ST3390 pathogenesis. At the host level, systemic mitochondrial dysfunction and interferon dysregulation emerged as hallmarks of host susceptibility to S. aureus. Collectively, these findings offer new insights into the molecular determinants of invasive S. aureus infection from both a host and bacterial perspective.

Download

Included in

Cell Biology Commons

Share

COinS