PROJECT 3 - Infection-Induced Remodeling of the Vascular Proteome

Project Summary, UC San Diego, Project 3 The aims of Project 3 address the central hypothesis of the overall program: Protein glycosylation and glycoprotein remodeling alter the coagulopathy and inflammation of sepsis. Project 3 will investigate remodeling of the vascular glycocalyx induced by sepsis and how these changes affect host response and survival in mice. The proposed research engages all of the core facilities of the program and draws on the combined expertise of the Project Leaders and Core Leaders in infection and sepsis, inflammatory biology, coagulation, proteomics and glycobiology. From recent literature and preliminary data, it is well known that sepsis induces changes in the composition of plasma glycoproteins and shedding of the vascular endothelial glycocalyx, leading to vascular dysfunction and high mortality. However, little information is available about the composition of the vascular proteome and glycoproteome and how it changes in response to different infectious agents. Over the last grant cycle, we developed an in vivo tagging method that allows assessment of the vascular proteome in different organs. We showed that infection by methicillin-resistant Staphylococcus aureus (MR) results in remodeling of the vascular proteome in an organ-specific manner, leading to the discovery of proteoglycan 4 and factors that modulate hyaluronan metabolism as potential novel markers of infection. We also showed that heparan sulfate produced by the vascular endothelium plays an important role in determining the severity and outcome of sepsis in mice. In the liver, undersulfation of endothelial heparan sulfate protects against the inflammatory response and coagulopathy induced by MR. However, in the heart, pathological changes take place that correlate with hypersensitivity to Staphylococcus aureus alpha-hemolysin, a key virulence factor. In the next cycle, we will expand the in vivo tagging method to include other common bacterial pathogens that cause sepsis in humans in order to identify operative pathogenic mechanisms and to determine if sepsis can be stratified by responses in the vascular wall to different pathogens. We will examine the mechanism by which heparan sulfate modulates alpha-hemolysin sensitivity. We will determine if the induction of proteoglycan 4 and hyaluronan metabolism are general hallmarks of sepsis and if these factors serve a protective role. We also showed that proteoglycan 4 and hyaluronan accumulate in human plasma samples from patients with sepsis. We will correlate these markers with clinical information about the patients to determine if these markers stratify sepsis and whether they have value as diagnostic or prognostic markers. The overarching goal is to understand if infection-induced remodeling of the vascular glycoproteome provides a window to identify disease mechanisms and a way to stratify sepsis across time, different infectious agents, and during disease resolution.