Date of Award
Doctor of Philosophy (PhD)
A multitude of cellular functions are controlled by the activity of the membrane-bound
protease TACE, including immune response and development. Through cleavage of its
membrane anchored substrates, TACE can activate a myriad of signaling pathways in
an auto- or paracrine manner, transferring signals across a tissues and systems.
Despite its importance, it is highly debated how TACE is regulated. I helped generate
TSen, a fluorescence-based sensor of TACE activity, a critical tool that proved
necessary to interrogate the underlying signaling that leads to TACE activation. TSen
enabled us to uncover a wide variation between cell lines and their underlying signaling
in regards to TACE which may account for much of the confusion about its regulation.
Furthermore, we used this sensor to find that TACE is intimately tied actin cytoskeletal
dynamics, which appears to be a novel mechanism of TACE activation. I then used
TSen to monitor TACE activity in single cells in conjunction with an ERK reporter to
measure both activities simultaneously for the first time. I was able to confirm past
results showing the propagation of ERK pulses from cell to cell, as well as identify a
new type of activity pulse: spikes in ligand shedding. These pulses of TACE activity
occur in neighbor cells prior to an ERK pulse, which is followed by another spike in
ligand shedding, validating the model that ERK pulses propagate between cells through
ligand shedding. I then probed cell junctions for their role in TACE signaling. Because
the aggressiveness of an epithelial-derived cancer is highly correlated with loss of cell
junctions, I generated an α-catenin knockdown in HaCaT cells, recreating a phenotype
of mesenchymal morphology and hyper proliferation. I found that silencing α-catenin in
this system generates a large increase in ligand shedding and subsequent proliferation
and that the hyper proliferative phenotype does not occur in the absence of TACE. My
findings contribute to the overall understanding of TACE regulation, as well as the
downstream effects of this signaling molecule in ERK pulses and proliferation.
Bunker, Eric Newman, "Novel Insights into Tace Regulation of Autocrine and Paracrine Signaling in Epithelial Cells" (2017). Chemistry & Biochemistry Graduate Theses & Dissertations. 216.