Molecular Mechanisms Underlying The Human Neutrophil Response To Fungal Beta-Glucan In The Context Of The Extracellular Matrix Protein Fibronectin

Johnson, Courtney Michele

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Year:: 2015
Contributor:: Johnson, Courtney Michele (creator); Reichner, Jonathan (Director); Bowen, Wayne (Reader); Bliss, Joseph (Reader); Sanders, Jennifer (Reader); Luscinskas, Francis (Reader); Fast, Loren (Director); Brown University. BIOMED: Pathobiology (sponsor)
Genre:: theses
Subject:: Complement Receptor 3; Beta-glucan; Integrins
Extent:: 27, 265 p.
DOI: https://doi.org/10.7301/Z0V40SMS

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Abstract:: Complement Receptor 3 (CR3), a β2 integrin found on neutrophils, plays an important role in fungal recognition and immune response. Co-ligation of CR3 with fibronectin (Fn), an ubiquitous extracellular matrix component, at the I-domain and β-glucan (B), a glucose polymer found in fungal cell walls, at the lectin-like domain is possible due to spatially distinct locations. Dual ligation of CR3 with Fn+B induces homotypic aggregation of primed neutrophils, a response representative of the immune cells encounter with fungi within tissues and that can be blocked by anti-CR3 antibody. Previous findings have shown that CR3-mediated DNA Neutrophillic Extracellular Traps (NETS) coincide with PMN aggregates. To understand the molecular mechanisms of how CR3 coordinates these neutrophil responses, this thesis explores the role of the integrins CR3 as well as the β1 integrin family members VLA3 and VLA5. Using antibody blockade and receptor-FRET, we unexpectedly discovered a CR3-mediated required role for VLA3, the canonical laminin receptor, in aggregate formation. The role of VLA3 in aggregate formation was specific as blockade of other β1 integrin family members such as VLA5, the canonical Fn receptor, failed to prevent aggregation. Exploring the role of VLA5, we were able to show a decrease in overall VLA5 activity on Fn+B and by using an activating anti-VLA5 antibody, that active inhibition of VLA5 activity is necessary for aggregate formation. In assessing NETs formation, we discovered that unlike aggregate formation, VLA5 and CR3 are necessary for NET formation, where VLA3 is not. Furthermore, activation of VLA5 with the activating VLA5 antibody does not inhibit NET formation. Finally, a correlative signaling role for p-ERK and p-GSK-3β was determined in the neutrophil responses to β-glucan and Fn but not to either alone. Within this thesis, a novel, complex and temporally regulated cross-talk pathway was uncovered in which dual ligation of CR3 signals the differential regulation of individual β1 integrins not often associated with anti-fungal activity. Furthermore, it was discovered that NETosis and aggregation are controlled by the activation state of distinct β1 integrins, VLA5 and VLA3, respectively.
Notes:: Thesis (Ph.D. -- Brown University (2015)

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Johnson, Courtney Michele, "Molecular Mechanisms Underlying The Human Neutrophil Response To Fungal Beta-Glucan In The Context Of The Extracellular Matrix Protein Fibronectin" (2015). Pathobiology Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0V40SMS

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Pathobiology Theses and Dissertations

Theses and Dissertations for the Pathobiology department.
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