Investigating the functions and molecular mechanisms of protein O-phosphorylation in Streptococcus mutans

About This Grant

Project Summary Streptococcus mutans is the primary bacterial agent of dental caries (cavities), a widespread disease affecting billions worldwide. The pathogen's ability to cause disease stems from its remarkable capacity to adapt to the harsh and dynamic oral environment, a process controlled by sophisticated regulatory networks. This proposal focuses on a key, yet underexplored, regulatory mechanism known as O-phosphorylation, a post- translational modification that reversibly alters protein function to control cellular processes. Our preliminary phosphoproteomic analysis of S. mutans has revealed that O-phosphorylation is widespread, affecting numerous proteins critical for stress adaptation, metabolism, and cell division. However, the functional significance of these phosphorylation events remains largely unknown. The central hypothesis of this application is that O-phosphorylation is a critical stress-responsive regulatory mechanism that modulates protein function to promote S. mutans adaptation and virulence. To test this hypothesis, we will pursue three specific aims. Aim 1 will determine the functional impact of O- phosphorylation on S. mutans physiology by systematically generating and screening the first-ever arrayed panel of phospho-mutants for any bacterial species, creating a functional map of the phosphoproteome. Aim 2 will investigate the role of the PppL phosphatase in cell division by dissecting a novel "altered-function" suppressor mutation that rescues a lethal phenotype, providing mechanistic insight into a critical cell division checkpoint. Aim 3 will examine the phosphorylation-mediated regulation of the Pgf glycosylation machinery, a key virulence pathway, to uncover a novel paradigm of regulatory crosstalk between O-phosphorylation and O-glycosylation. Successful completion of this project will fundamentally advance our understanding of bacterial signal transduction. It will deliver a novel functional map linking specific phosphorylation events to virulence, provide a detailed molecular mechanism for two key regulatory pathways controlling cell division and glycosylation, and establish a foundational resource for the field. Ultimately, this work is expected to uncover novel, druggable targets, paving the way for the development of new therapeutic strategies to combat dental caries.