Cell Biology Commons^™

Elucidating The Biomechanics Of Mertk-Mediated Efferocytosis, Brandon Hayato Dickson

Electronic Thesis and Dissertation Repository

Macrophages are key mediators of efferocytosis – the phagocytic engulfment and removal of apoptotic cells. During engulfment, the coordinated activity of efferocytic receptors induces the remodeling of the actin cytoskeleton, which facilitates the envelopment of the cell by the plasma membrane. Mer receptor tyrosine kinase (MERTK) is a crucial efferocytic receptor, but its role during actin remodeling is not well understood. Previously, our lab showed that MERTK is an activator of β₂ integrins – which are comprised of receptors known to induce the actin polymerization that is required for engulfment. We hypothesized that MERTK is an indirect stimulator of …

The Regulation Of Pannexin1 And Pannexin2 In The Skin In Health And Disease, Rafael E. Sanchez Pupo

Electronic Thesis and Dissertation Repository

Pannexins (PANX1, 2, 3) are a family of channel-forming glycoproteins that mediate intracellular and paracrine signaling. In contrast to PANX2, PANX1 has been extensively investigated in the skin, modulating cell differentiation, wound healing, and melanoma development. PANX1 and PANX2 can co-exist in the same cell and form mixed channels where their glycosylation seems to regulate their intermixing. N-glycosylation and caspase cleavage have been proposed as modulators of the function of PANX1, but their effects on PANX2 are unknown. We explored the PANX2 expression in mouse skin and showed that a Panx2 splice variant (PANX2-202) is continuously expressed throughout aging skin. …

The Role Of Pu.1 In Lipid Metabolism And Cell Cycle Regulation In Myeloid Progenitor Cells, Jess Rhee

Electronic Thesis and Dissertation Repository

PU.1 is a transcription factor essential for myeloid development. High PU.1 levels promote cell cycle arrest and differentiation. Low levels promote proliferation and have been associated with leukemia. BN mice are homozygous for a hypomorphic allele of Spi1 that results in expression of PU.1 at 20% of normal levels. Induction of PU.1 expression in BN myeloid progenitor cells causes cell cycle arrest, differentiation, and the upregulation of microRNAs targeting lipid metabolic genes. Acly encoding ATP citrate lyase (ACL) was one of these targets. ACL produces acetyl-CoA which is essential for fatty acid synthesis. We hypothesized that inhibiting ACL would cause …

Characterizing Ferroportin Trafficking In Macrophages During Phagocytosis, Tayler J. Farrell

Electronic Thesis and Dissertation Repository

Macrophages are important mediators of innate immunity and nutritional immunity via modulation of essential nutrients like iron during bacterial infection. Ferroportin (Fpn), an iron-exporting protein, is found on the plasma membrane of macrophages and, if not modulated during phagocytosis, would transport iron into phagosomes and supply phagocytosed bacteria with iron. Interestingly, the fate of Fpn during phagocytosis and bacterial infection remains unknown. We generated a Fpn-GFP fusion protein and, using fluorescence microscopy, demonstrated that, during phagocytosis in RAW264.7 macrophages, Fpn is removed from phagosomes containing IgG-coated beads or Staphylococcus aureus. Further, Fpn is present on Rab5-containing phagosomes but absent …

Elucidating The Signalling Pathway Of Mer Tyrosine Kinase Receptor In Efferocytosis, Ekenedelichukwu Azu

Electronic Thesis and Dissertation Repository

Efferocytosis is the clearance of apoptotic cells and is necessary for homeostasis. Mer Tyrosine Kinase (MerTK) is a crucial efferocytic receptor whose loss is associated with chronic inflammatory diseases and autoimmunity. While previous studies have shown that MerTK mediates efferocytosis through a unique mechanism that requires integrins, MerTK signalling pathway remains unknown. Given this unusual internalization mechanism, I hypothesized that MerTK signals and engages integrins through a novel signalling pathway different from that used by other phagocytic receptors. Therefore, this study aimed to identify the signalling pathways activated by MerTK, utilizing conventional cell biology and pharmacological approaches.

I found that …

Characterization Of Efferosome Maturation And The Processing Of Apoptotic Bodies, Yohan Kim

Electronic Thesis and Dissertation Repository

Every day billions of cells in our bodies undergo apoptosis and are cleared through efferocytosis – a phagocytosis-like process in which phagocytes engulf and degrade apoptotic cells. Proper processing of efferosomes prevents inflammation and immunogenic presentation of antigens. In this thesis I determined that the early stages of efferosome maturation parallel that of the pro-immunogenic phagocytosis of pathogens. Mass spectrometry analysis of later maturation stages identified unique regulatory proteins on efferosomes and phagosomes. Keys among these were Rab17 and Rab45 on efferosomes versus Rab6b and PI-4-Kinase on phagosomes. The later would allow for antigen presentation from phagosomes, while the former …