ORCID

http://orcid.org/0000-0002-4247-0647

Date of Award

Spring 5-15-2022

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Immunology)

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Regulation of epithelial turnover is essential for the maintenance of the structure and function of the intestine. The balance of intestinal epithelial turnover is known to be modulated by cell-extrinsic cytokines such as Tumor Necrosis Factor (TNF). Likewise, cell-intrinsic modulation of survival and death is afforded by a highly-conserved, multi-step pathway termed autophagy. In this body of work, I have characterized a specific and potent role for autophagy in protecting mouse intestinal epithelial cells (enterocytes) from TNF-triggered cell death. Specifically, I have found that the autophagy initiation factor Atg14 is central to mediating this protective role. Utilizing conditional loss of function mouse models of Atg14 and its upstream regulator Rb1cc1/Fip200, I have demonstrated that canonical autophagy factors are required for maintenance of the intestinal architecture and the viability of enterocytes. I furthermore demonstrate through genetic and pharmacologic approaches that TNF signaling through its cognate receptor Tnfr1 is required for the induction of apoptotic death of autophagy-deficient enterocytes. Through a candidate approach to profile the TNF signaling and autophagic pathways in the Atg14 deficient mouse cell, I have identified both an autophagy associated factor (Sqstm1/p62) and a TNF induced cell death factor (Cflar/Cflip) isoform that accumulate within the autophagy deficient mouse cell. Genetic ablation of Sqstm1/p62 rescues mouse intestinal architecture and epithelial cell death within the Atg14 deficient mouse model. These findings define the critical molecular pathways that mediate sensitivity to apoptosis in the Atg14 deficient mouse enterocyte. Lastly, my research has identified that human ATG14 KO cells (HeLa) share a defect in SQSTM1/p62, but are not sensitive to enhanced TNF-triggered death, and do not express the pathogenic isoform of the cell death regulator CFLAR/CFLIP. This finding lays the foundation for further basic science research to understand the divergence between human and mouse with respect to cell death pathways. This work provides insight into the limited success, thus far, of autophagy-oriented therapeutics in the context of human disease, while promoting novel approaches for such therapies.

Language

English (en)

Chair and Committee

Thaddeus S. Stappenbeck

Committee Members

Clay F. Semenkovich

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