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Author ORCID Identifier
https://orcid.org/0009-0003-4033-5809
Date Available
8-5-2028
Year of Publication
2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
College
Arts and Sciences
Department/School/Program
Chemistry
Faculty
Samuel G. Awuah
Faculty
Kenneth Graham
Abstract
The endoplasmic reticulum (ER) chaperone, glucose-regulated protein (GRP78)/binding immunoglobulin protein (BiP)/HSPA5, is a master regulator of Proteostasis, regulating protein folding, the Unfolded Protein Response (UPR), and Endoplasmic Reticulum-associated degradation (ERAD). GRP78 is often overexpressed in many cancers, and this vulnerability has been therapeutically targeted, but therapeutic success has been hampered by resistance and immunosuppression. Despite the availability of a few GRP78 inhibitors, none have received clinical approval, highlighting a critical need for new therapeutic strategies. Further, the scaffolding functions of GRP78 remain underexplored, and its potential role as a client hub that promotes resistance is not well understood. Targeting ER resident proteins, such as GRP78, for degradation remains a significant challenge because they are largely inaccessible to current targeted degradation approaches. Here, I report the development of peptidomimetic degraders as first-in-class small-molecule scaffolds designed to engage the substrate-binding domain of the ER chaperone GRP78 and initiate its selective degradation via the endogenous ER-associated degradation (ERAD) pathway.
Using integrated computational, biochemical, cellular, and multi-omic approaches, my research shows that peptidomimetic degraders reshape the conformational dynamics of GRP78/BiP, thereby promoting organelle-localized ligase recruitment and proteostatic clearance. Our lead candidate, SGA01, modulates an unrecognized GRP78 regulatory circuit, characterized by transcriptional induction of UNC5B and concomitant depletion of SHP2 protein. SGA01 also exhibits favorable metabolic and plasma stability, demonstrates robust pharmacodynamic kinetics with tumor growth suppression in triple-negative breast cancer models, and has no off-target effects. Together, these findings establish a chemical strategy for enforcing ER-restricted protein degradation and provide a tractable framework for targeting chaperone addiction across various malignancies.
These GRP78 degraders further elucidated the molecular consequences of GRP78 depletion, including disruption of mitochondrial function and ER-mitochondria crosstalk. SGA01-induced degradation of GRP78 causes ER stress, and uncontrolled ER stress amplifies beyond the ER to the mitochondria, leading to disruption of ER mitochondrial crosstalk and mitochondrial dysfunction. SGA01-based probes were designed to map GRP78 protein interactions. In addition to the dipeptide-based peptidomimetic, further development efforts have extended to tripeptides to elucidate the binding rules governing GRP78 degradation.
In conclusion, we provided a framework for GRP78-targeted degradation using small-molecule peptidomimetics and elucidated the impact of this degradation on other organelles, such as mitochondria, and its relevance in disease models.
Digital Object Identifier (DOI)
https://doi.org/10.13023/etd.2026.421
Archival?
Archival
Funding Information
This work was supported by grant R01CA258421- 01 from the National Cancer Institute.
Recommended Citation
Daraezinwa, Jovita Ogechi, "CHEMICAL BIOLOGY OF ER CHAPERONE, GRP78" (2026). University of Kentucky Doctoral Dissertations. 871.
https://uknowledge.uky.edu/gradschool_diss/871
