Electronic Thesis and Dissertation Repository


Master of Science


Microbiology and Immunology


Heit, Bryan


Mer tyrosine kinase (MERTK) is a receptor tyrosine kinase which mediates efferocytosis-the recognition and uptake of apoptotic cells. MERTK serves as the predominant efferocytic receptor in several tissues, including in the heart, with single nucleotide polymorphisms associated with up to a 75% increased risk of atherosclerosis in humans. MERTK facilitates the internalization of apoptotic cells via a MERTK/integrin pathway that involves, in part, PI-3-kinase signaling and signaling via Src-family kinases. While these elements of the MERTK signaling pathway have been identified, much of MERTK’s signaling mechanisms remain to be elucidated. Pharmacological inhibitors were used to block signaling through canonical phagocytic signaling pathways, and through signalling molecules identified as part of the MERTK signalosome by mass spectrometry, and the efferocytosis of MERTK-specific targets assessed using a human macrophage cell line. These experiments identified PI3K, Src, Syk, ERK, and ILK as regulators of MERTK efferocytic function. To identify non-canonical pathways, we began the development of a CRISPR-tagged endogenous MERTK allele which can be selectively activated in a human macrophage cell line without inadvertent activation of other phagocytic receptors; using this cell line and phosphoprotein mass spectrometry, future studies will be able to identify non-canonical tyrosine-kinase dependent pathways mediating MERTK efferocytic function. Identification of these pathways will elucidate the signaling pathway utilized by MERTK, and potentially may identify signaling pathways which drive aberrant MERTK function during diseases such as atherosclerosis.

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