Abstract 287: Novel p62 interaction suggests novel role in glutamate metabolism

Abstract

Abstract Prostate cancer (PCa) is the second most common cause of cancer-related death among American men. Androgen Receptor (AR) transcriptional activity is required for PCa tumor growth. Thus, androgen deprivation therapy (ADT) is a first line PCa therapy. However, 10-20% of patients will inevitably develop lethal castration-resistant PCa (CRPC). Thus, we must uncover the mechanisms that drive CPRC. Chronic inflammation is a known hallmark of cancer initiation and progression. Using the LNCaP human PCa cell line, we have shown that chronic exposure to the inflammatory cytokine, interleukin-1 (IL-1) can transform castration-sensitive PCa cells into castration-resistant PCa cells. IL-1 is elevated in PCa patient tissue and serum and is associated with disease progression and metastasis. IL-1 is clinically relevant, but the role of IL-1 in CRPC development is not fully elucidated. To mimic ADT, we serum-starved LNCaP and the chronic IL-1 sublines, LNas1 and LNbs1, and performed mass spectrometry to identify chronic IL-1-induced changes in protein-protein interactions. Specifically, we looked at p62 protein interactors. p62 is a multi-domain, multifunctional pro-survival protein that mediates autophagic flux in response to cellular stress and serum starvation, promotes NF-κB inflammatory signaling and induces NRF2 antioxidant signaling. We discovered that p62 forms a constitutive interaction with KEAP1 under serum starved and normal growth conditions in the chronic IL-1 sublines. KEAP1 inhibits NRF2 nuclear translocation. In response to antioxidant stress, p62 binds and sequesters KEAP1 from NRF2 to activate NFR2 signaling. Surprisingly, we do not observe constitutive canonical NRF2 signaling in the chronic IL-1 sublines. However, in response to serum starvation, we do see both high basal levels and upregulation, specifically, of the NRF2-induced gene, GCLC. GCLC is a glutamate-cysteine ligase that synthesizes the antioxidant, glutathione. Therefore, using mass spectrometry and immunoprecipitation western blotting, we looked at p62 interactions under serum starvation conditions. While we did not find p62 interaction with GCLC in the chronic IL-1 sublines, we do find that p62 interacts with GLUL. GLUL is a glutamate-ammonia ligase that plays a role in cellular detoxification. These data suggests that chronic IL-1 exposure induces novel p62 interactions that have a role in glutamate metabolism. Citation Format: Haley Christine Dahl, Anisha R. Konakalla, Preethi Kanumuri, Basir Mansoor, Anastasia Kelley, Riya Shipurkar, Nikki A. Delk. Novel p62 interaction suggests novel role in glutamate metabolism [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 287.