Abstract B007: Investigation of the mechanism of PADI2 regulation by the FBXW7 tumor suppressor

Abstract

Abstract Serous endometrial cancer (SEC) is an aggressive form of cancer that frequently exhibits recurrent somatic mutations in FBXW7 at residues 465, 479, and 505. FBXW7 is a tumor suppressor and is part of a Skp1-Cullin-F-box containing (SCF) complex that targets various proteins, including certain oncoproteins, for ubiquitin-mediated proteasomal degradation. FBXW7 interacts with Cdc4 phosphodegron (CPD) motif(s) within substrate proteins. We previously reported upregulation of peptidyl arginine deiminase 2 (PADI2), a potentially druggable protein, in FBXW7-mutant SEC cell lines compared to the isogenic FBXW7-wildtype cells. The purpose of this study is to investigate the mechanism by which FBXW7 regulates PADI2 levels. We searched for the CPD motif in the PADI2 protein sequence. We used co-immunoprecipitation and immunoblotting to study FBXW7-PADI2 interactions after transiently transfecting HEK293 cells with constructs expressing MYC-tagged FBXW7 and/or HA-tagged PADI2, in the presence or absence of bortezomib. We identified three putative CPD motifs in PADI2, leading us to hypothesize that wildtype FBXW7 binds PADI2 and thus targets PADI2 for degradation via a proteasome-dependent mechanism. Our experimental data show that FBXW7 interacts with PADI2, in the presence of bortezomib, a proteasome inhibitor, in transiently transfected HEK293 cells. Additionally, we have shown that mutation of the putative CPD motifs of PADI2 abrogates the PADI2-FBXW7 interaction. Our findings implicate PADI2 as a novel substrate of the FBXW7 tumor suppressor. Citation Format: Chandra Mani Kafle, Daphne W. Bell. Investigation of the mechanism of PADI2 regulation by the FBXW7 tumor suppressor [abstract]. In: Proceedings of the AACR Special Conference on Endometrial Cancer: Transforming Care through Science; 2023 Nov 16-18; Boston, Massachusetts. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(5_Suppl):Abstract nr B007.