Hospital-acquired infections derived from various pathogens including P. aeruginosa (Pa) require approximately $45 billion in annual medical expenses in the U.S., according to the CDC. Despite intense interest, the function of alveolar macrophages (AM) in Pa infection remains elusive. Macroautophagy (hereafter autophagy) is a conserved homeostasis mechanism by which cellular components are sequestered to autophagosomes for degradation through ubiquitination. The autophagosome machinery may contribute to the innate immunity to enhance bacterial clearance. However, it is unknown whether autophagy impacts Pa infection. Our preliminary data revealed that Pa infection can induce autophagy, and subsequently increasing bacterial degradation. We also showed that the pleiotropic Src kinase, Lyn, interacts with toll like receptors (TLRs) to boost autophagic activity In addition, we found that Atg-7 is critical for phagosome-lysosome fusion. Importantly, starvation increases AM phagocytosis of Pa and blocking autophagy by autophagy inhibitor 3-methyladenine (3MA) decreased phagocytosis and subsequent bacterial clearance. Thus, we hypothesize that Pa-induced autophagy augments host defense by facilitating phagocytosis and bacterial degradation. Our long-term goal is to discover the key factors required for regulating host defense against Pa invasion in order to develop novel therapeutic strategies. The objective of this proposal is to examine the physiological significance of Lyn/Atg-7 modulated phagocytosis with KO mice and to delineate the underlying molecular mechanisms using biochemical and whole animal imaging approaches.
Aim 1 : Define the functional role of Atg-7 in Pseudomonas pulmonary infection. Our working hypothesis is that atg-7 is required for protection against Pa infection.
Aim 2 : Evaluate the impact of autophagy on phagocytosis in pulmonary bacterial infection utilizing a mouse model and primary mouse AM. Based on our finding that Pa infection can induce autophagy and reducing bacterial burdens in AM, our working hypothesis is that Pa-induced autophagy augments macrophage phagocytosis.
Aim 3 : Determine the role of TLR-2, Lyn, and Atg-7 in autophagosome formation and phagolysosome fusion in host response against bacteria. Thus, our working hypothesis is that TLR-2, Lyn, and Atg-7 are key elements for delivery of bacteria to lysosomes for degradation. These proposed studies will reveal a novel mechanism for AM to eradicate bacteria and suggest novel therapeutic targets.
Hospital-acquired infections impose $45 billion in annual medical expenses in the U.S., according to the CDC and Pseudomonas aeruginosa (Pa) is the fourth most commonly-isolated nosocomial bacterium. Using novel mouse models and whole animal imaging, studying novel roles of autophagy (cell self-eating) in bacterial pathogenesis will substantially advance our understanding of the function of alveolar macrophages (AM) in host defense against microbes. This application will ultimately reveal new therapeutic targets for controlling Pa and potentially other Gram-negative bacteria.
|Zhu, Miao; Zhao, Jingru; Kang, Huaping et al. (2016) Corrigendum: Modulation of Type III Secretion System in Pseudomonas aeruginosa: Involvement of the PA4857 Gene Product. Front Microbiol 7:881|
|Li, Xuefeng; He, Sisi; Zhou, Xikun et al. (2016) Lyn Delivers Bacteria to Lysosomes for Eradication through TLR2-Initiated Autophagy Related Phagocytosis. PLoS Pathog 12:e1005363|
|Zhu, Miao; Zhao, Jingru; Kang, Huaping et al. (2016) Modulation of Type III Secretion System in Pseudomonas aeruginosa: Involvement of the PA4857 Gene Product. Front Microbiol 7:7|
|Zhao, Jingru; Yu, Xiang; Zhu, Miao et al. (2016) Structural and Molecular Mechanism of CdpR Involved in Quorum-Sensing and Bacterial Virulence in Pseudomonas aeruginosa. PLoS Biol 14:e1002449|
|Zhuang, Yan; Li, Yi; Li, Xuefeng et al. (2016) Atg7 Knockdown Augments Concanavalin A-Induced Acute Hepatitis through an ROS-Mediated p38/MAPK Pathway. PLoS One 11:e0149754|
|Li, Xuefeng; He, Sisi; Li, Rongpeng et al. (2016) Pseudomonas aeruginosa infection augments inflammation through miR-301b repression of c-Myb-mediated immune activation and infiltration. Nat Microbiol 1:16132|
|Zhou, Xikun; Ye, Yan; Sun, Yuyang et al. (2015) Transient Receptor Potential Channel 1 Deficiency Impairs Host Defense and Proinflammatory Responses to Bacterial Infection by Regulating Protein Kinase CÎ± Signaling. Mol Cell Biol 35:2729-39|
|Cochrane, Stephen A; Li, Xuefeng; He, Sisi et al. (2015) Synthesis of Tridecaptin-Antibiotic Conjugates with in Vivo Activity against Gram-Negative Bacteria. J Med Chem 58:9779-85|
|Wu, Xu; Chen, Jiao; Wu, Min et al. (2015) Aptamers: active targeting ligands for cancer diagnosis and therapy. Theranostics 5:322-44|
|Li, Rongpeng; Tan, Shirui; Yu, Min et al. (2015) Annexin A2 Regulates Autophagy in Pseudomonas aeruginosa Infection through the Akt1-mTOR-ULK1/2 Signaling Pathway. J Immunol 195:3901-11|
Showing the most recent 10 out of 13 publications