The emigration of peripheral blood neutrophils to a site of infection includes a central role of integrins within the beta-2 family. Neutrophils use these integrins to adhere to endothelial cells located in the vicinity of infection and subsequently to extracellular matrix in order to guide their navigation towards the pathogen. The beta-2 integrin CR3 (CD11b/CD18) is a unique receptor in that it has two distinct ligand binding sites, the I-domain which recognizes cell adhesion molecules, complement components and extracellular matrix;and the lectin domain which binds carbohydrate such as beta-glucan and those expressed on glycosylphosphatidyl inositol-anchored receptors. Beta-glucan is a polymer of glucose moieties in (1,3)(1,6)-beta-D-linkages found normally as a structural component of the fungal cell wall and is a functional agonist of the CR3 lectin site. During the current funding period we found than a number of CR3-dependent neutrophil functions are regulated differently in response to ligation of the I-domain, the lectin site, or both together. Experiments are proposed in this continuation to determine the mechanism/s that explain how a single receptor can transduce such different cellular affects when ligated at its distinct binding sites.
The specific aims of this proposal are: (I) to determine the dynamic regulation and spatial localization of CR3 upon differential activation of the I-domain and the lectin site;(II) to determine the signal transduction pathways that mediate the conversion of random to directed migration of human neutrophils upon activation of the CR3 lectin site;(III) to determine the role of CR3 lectin site activation on host defense in vivo. Given the importance of CR3 in every aspect of leukocyte function, a better understanding of the complex regulatory mechanisms that control its function may lead to better treatment of the pathological conditions that result from its dysregulation. Hyperactivity can lead to pathologies such as autoimmune diseases, multiple sclerosis, inflammatory bowel disease, psoriasis, and arthritis. Insufficient function can result in recurrent infection and failure to heal wounds. Therapies that target CR3 may be developed to safely and effectively enhance leukocyte function in presurgical or cancer patients or those following trauma, sepsis, wounding, aging or immunosuppression. The underlying premise of this proposal is that a better understanding of leukocyte integrin regulation may reveal that integrins represent therapeutic targets for safe and effective regulation of the innate immune system.
Inflammation is an essential response to injury or infection as it prevents infections from becoming widespread and begins the process of healing. White blood cells (leukocytes) circulate continuously in the bloodstream but in response to a local site of injury, they must emigrate from the blood into the damaged tissue to begin healing. The focus of this proposal is to help determine how circulating white blood cells sense the location of a tissue injury and migrate directly to the exact spot. Cell surface receptors known as integrins are necessary for leukocytes to navigate properly and are the subject of this proposal.
|Biron, Bethany M; Chung, Chun-Shiang; O'Brien, Xian M et al. (2017) Cl-Amidine Prevents Histone 3 Citrullination and Neutrophil Extracellular Trap Formation, and Improves Survival in a Murine Sepsis Model. J Innate Immun 9:22-32|
|O'Brien, Xian M; Biron, Bethany M; Reichner, Jonathan S (2017) Consequences of extracellular trap formation in sepsis. Curr Opin Hematol 24:66-71|
|Johnson, Courtney M; O'Brien, Xian M; Byrd, Angel S et al. (2017) Integrin Cross-Talk Regulates the Human Neutrophil Response to Fungal ?-Glucan in the Context of the Extracellular Matrix: A Prominent Role for VLA3 in the Antifungal Response. J Immunol 198:318-334|
|Byrd, Angel S; O'Brien, Xian M; Laforce-Nesbitt, Sonia S et al. (2016) NETosis in Neonates: Evidence of a Reactive Oxygen Species-Independent Pathway in Response to Fungal Challenge. J Infect Dis 213:634-9|
|Stout, David A; Bar-Kochba, Eyal; Estrada, Jonathan B et al. (2016) Mean deformation metrics for quantifying 3D cell-matrix interactions without requiring information about matrix material properties. Proc Natl Acad Sci U S A 113:2898-903|
|Toyjanova, Jennet; Flores-Cortez, Estefany; Reichner, Jonathan S et al. (2015) Matrix confinement plays a pivotal role in regulating neutrophil-generated tractions, speed, and integrin utilization. J Biol Chem 290:3752-63|
|Loosley, Alex J; O'Brien, Xian M; Reichner, Jonathan S et al. (2015) Describing directional cell migration with a characteristic directionality time. PLoS One 10:e0127425|
|O'Brien, Xian M; Loosley, Alex J; Oakley, Katie E et al. (2014) Technical advance: introducing a novel metric, directionality time, to quantify human neutrophil chemotaxis as a function of matrix composition and stiffness. J Leukoc Biol 95:993-1004|
|Fox, Elizabeth D; Heffernan, Daithi S; Cioffi, William G et al. (2013) Neutrophils from critically ill septic patients mediate profound loss of endothelial barrier integrity. Crit Care 17:R226|
|Brancato, Samielle K; Thomay, Alan A; Daley, Jean M et al. (2013) Toll-like receptor 4 signaling regulates the acute local inflammatory response to injury and the fibrosis/neovascularization of sterile wounds. Wound Repair Regen 21:624-633|
Showing the most recent 10 out of 25 publications