Abstract 1695: Guanylate binding protein 1 modulate the proteasomal machinery and causes the cytochrome C degradation

Abstract Guanylate Binding Protein 1 (GBP1) is known as an interferon γ induced GTPase. It plays a crucial role in innate immunity against pathogenic infections but its role in cancer and therapeutic response is not well understood. Therefore, to study the role of GBP1, we investigated genetically manipulated ovarian cancer cells. We have employed in vitro and in vivo studies along with a proteomics approach to uncover the protein-protein interactions and their crosstalk with GBP1. The data suggest that GBP1 knockdown (KD) inhibits the clonogenic potential of cancer cells. In vivo studies including subcutaneous xenograft and intraperitoneal models revealed that GBP1 overexpressing (OV) tumor cells growing faster and reduce the median survival of animals compared to vehicle control (VC). Whereas GBP1 KD tumors were progressing slowly with longer median survival compared to scrambled control (SC). To study the molecular interactions of GBP1, we performed a proteomics-based Cellular thermal shift assay (CETSA) on GBP1 OV and KD ovarian cancer cells. We found that GBP1 interacts with members of proteasome including PSMB1, PSMB6, PSMA3, and Cytochrome C (CYCS). Protein analysis showed that GBP1 over-expressing cells had less ubiquitinylated proteins compared to VC, whereas GBP1 KD cells accumulate the ubiquitinylated proteins compared to SC. We also found that the GBP1 KD cells are sensitive to paclitaxel treatment and accumulated ubiquitinylated proteins compared to SC. Moreover, GBP1 KD inhibits the overall proteasomal activity. Paclitaxel-treated GBP1 OV cells accumulated the ubiquitination of CYCS, followed by clearance of cytosolic CYCS. Furthermore, global proteome profiling also suggests that GBP1 KD induces apoptotic pathways whereas GBP1 OV induces pathways associated with the stress response. Overall, the results from our studies elucidate the role of GBP1 in chemotherapeutic stress response via the activation of proteasomal machinery. Citation Format: Dhanir Tailor, Fernando Jose Garcia-Marques, Abel Bermudez, Sharon J. Pitteri, Sanjay V. Malhotra. Guanylate binding protein 1 modulate the proteasomal machinery and causes the cytochrome C degradation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1695.