Master of Science / Department of Biology / Rollie Clem / Apoptosis, or programmed cell death, is a crucial conserved process among
organisms for deleting damaged unwanted cells, as well as for development and viral
defense, and plays an important role in multiple diseases. Too much apoptosis may lead
to Alzheimer’s disease, and too little may result in cancer. Therefore, the ability to
understand this process is essential for improved medical knowledge today. Apoptosis
has been explored in a number of species and pathways seem relatively conserved among
most, with unique aspects contained in each, but little is known about apoptosis in
mosquitoes. Improved knowledge and growing interest concerning apoptosis in
mosquitoes is necessary considering the vast health effects seen across the globe as a
result of diseases transferred by the mosquito vector. The Dengue virus mosquito vector
Aedes aegypti was the focus here. A new player named defense repressor 1 was
discovered in Drosophila melanogaster (DmDnr1), shown to play a role in apoptosis, and
the homolog discovered in A. aegypti (AeDnr1). Silencing Dmdnr1 resulted in cells
sensitized to apoptosis but was not enough to induce spontaneous apoptosis. In contrast,
silencing Aednr1 in the A. aegypti cell line, Aag2, led to spontaneously induced
apoptosis. This showed the importance of AeDnr1 as a member of the apoptotic pathway
in this species. Epistasis experiments showed that apoptosis induced by silencing Aednr1
requires the initiator caspase Dronc and the effector caspase CASPS8, whereas apoptosis
induced by silencing the inhibitor of apoptosis, Aeiap1, also requires Dronc but acts
through the effector caspase CASPS7. Further epistasis experiments showed that
apoptosis induced by silencing Aednr1 requires the IAP antagonist Mx, but not IMP.
This showed for the first time a gene regulating upstream of an IAP antagonist.
Biochemical studies showed that AeDnr1 regulates active CASPS8 but not CASPS7, and
interacts with Mx and CASPS8 but not AeDronc, CASPS7 nor AeIAP1. Studies also
showed Mx competes effectively with CASPS8 but not CASPS7 for AeIAP1 binding,
and IMP competes effectively with CASPS7 but not CASPS8 for AeIAP1 binding. An
improved apoptosis pathway for the mosquito A. aegypti emerged involving a potential feedback loop with explanations for the upstream IAP antagonist preference as well as
the downstream effector caspase preference resulting from apoptosis induced by Aednr1
silencing. Through the discussed research, multiple unique findings resulted. Studying
the mosquito model will allow us to find certain gene relations that are more difficult to
uncover in the Drosophila model. Because Dnr1 is found in most systems, this improved
pathway may shed light not only on a potential role of Dnr1 in apoptosis in insects but
higher organisms as well.
| Identifer | oai:union.ndltd.org:KSU/oai:krex.k-state.edu:2097/11972 |
| Date | January 1900 |
| Creators | Devore, Casey Leigh |
| Publisher | Kansas State University |
| Source Sets | K-State Research Exchange |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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