Date of Award


Document Type



Santa Clara : Santa Clara University, 2022.

Degree Name

Master of Science (MS)



First Advisor

Zhiwen Zhang


It has been understood that during Gram-positive bacterial infection, the bacterial cells interact with host mammalian cells via the virulence factors whose anchorage onto the bacterial surface are mainly catalysed by Sortase A[2]. Emergence of antibiotic-resistant bacterial strains, especially the Gram-positive bacteria, has rendered the rise of many antibiotic resistant bacteria, resulting in rise of infection cases that bypass traditional first-line antibiotics treatments. It is crucial for the public health that scientists and researchers discover an alternative treatment for the bacterial infection that targets the underlying pathogenic mechanism that are responsible for the increased virulence of such bacteria without contributing to the rise of antibiotic resistant bacteria. Recent studies of virulence of S.aureas infections have been associated with the identification of the numerous virulence factors such as styes, furunculosis, and paronychia, or to more serious infections, such as pneumonia, mastitis, urinary tract infections, osteomyelitis, endocarditis, and even sepsis[3] in which the pathways for pathogenesis are downstream processes that often require multiple targets of inhibition for therapeutic applications. However, while the current studies of virulence factors of S.aureas have identified various virulence factors, there remains much of individual virulence factor mechanisms that have yet to be discovered. Thus, the significance of identifying the messenger molecule in the upstream pathogenic pathway of Sortase A activity can pose an alternative solution for therapeutic application by direct inhibition of monomerization of Sortase A. We propose a mechanism with a bacteria-mammalian co-culture invasion assay, that suggests the degree of internalization of Gram-positive bacteria has been reduced by the presence of synthetic Neuropeptide-Y by it’s interaction with Neuropeptide-Y2 receptor expressed on the surface of mammalian cells. Based on our cross-linked proteomic study between Sortase A and mammalian cell proteomes, we found that the identified Neuropeptide Y (NPY) Y2 receptor with the bound ligand, NPY, can bind to Sortase A of S. aureus and regulate its monomer-homodimer equilibrium, which is responsible for the bacterial cell wall sorting activity. Our results suggest that the NPY Y2 receptor on the surface of the mammalian cell plays a fundamental role in initiating Gram-positive bacterial infections and promoting their pathogenicity.

Available for download on Tuesday, July 11, 2023