Bacterial pneumonia causes significant morbidity and mortality worldwide despite the availability of antibiotics. The immune system must balance the competing requirements of clearing the pathogen while avoiding local organ damage. There remains an unmet need for host-directed therapeutics that limit injury or promote resolution without impairing pathogen control. Neutrophils constitute the initial response to bacterial pneumonia and control infection through direct killing of bacteria and production of mediators including chemokines, cytokines, proteases and reactive oxygen species (ROS). This R03 application aims to define novel functions for the innate immune kinase TANK-binding kinase 1 (TBK1) in neutrophils during pneumonia. TBK1 promotes the expression of type 1 interferons (IFN) by phosphorylating transcription factors from the interferon regulatory family (IRF) during viral infection, but its functions in bacterial pneumonia and in neutrophils remain undefined. My K08 Award investigates how TBK1 functions in monocytes and macrophages during influenza infection. Data from that project and from our previous publication show that during S. pneumoniae pneumonia, lung neutrophils upregulate genes coding for TBK1 and its accessory proteins, but fail to express the common downstream product, type 1 IFN, suggesting that neutrophils use the TBK1 signaling module in a unique way. We find that in S. pneumoniae pneumonia, TBK1 is required for multiple aspects of neutrophil function, including elaboration of multiple cytokines, production of reactive oxygen species (ROS), and bacterial clearance. We hypothesize that neutrophil TBK1 regulates both IRF-dependent and IRF-independent transcriptional programs as well as other cellular programs such as metabolism. The proposed aims focus on identifying cellular and molecular details of TBK1 signaling in neutrophils in response to infection by S. pneumoniae.
In Aim 1, we will determine the transcriptional programs driven by TBK1 in lung neutrophils, characterizing in particular 1) the activation of transcription factors by assessing the expression of their target genes and 2) the expression of genes that regulate metabolic processes.
In Aim 2, we will determine how TBK1 promotes neutrophil ROS production, with a focus on NADPH oxidase assembly and neutrophil metabolism. We will assess glucose uptake, autophagy, and mitochondrial function in lung neutrophils from WT and TBK1 KO mice in the setting of pneumonia. The proposed studies will explore new functions for the kinase TBK1 with the ultimate goal of improving patient outcomes in this common form of lung injury. These studies diverge from my K08 Award through their focus on neutrophils and bacterial pneumonia and their need for technologies unfamiliar to me. They will increase the breadth and depth of my research program to engage both myeloid cell lineages and both viral and bacterial pathogens.
Bacterial pneumonia causes serious lung infections that kill hundreds of thousands of people worldwide yearly despite the availability of antibiotics. Neutrophils contribute to both host defense and lung damage, and how different proteins control this balance is unknown. We propose to study how the protein TANK-binding kinase 1 (TBK1) contributes to neutrophil anti-bacterial defense and lung inflammation, with the goal of finding therapies that prevent lung damage and speed healing without impairing bacterial clearance.
