Isoliquiritigenin (ISO) is a flavonoid extracted from the root of licorice, which serves various biological and pharmacological functions including antiinflammatory, antioxidation, liver protection, and heart protection. However, the mechanism of its action remains elusive and the direct target proteins of ISO have not been identified so far. Through cell-based screening, we identified ISO as a potent lipid-lowering compound. ISO treatment successfully ameliorated fatty acid-induced cellular lipid accumulation and improved nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) by increasing PPARα-dependent lipid oxidation and decreasing SREBPs-dependent lipid synthesis. Both these signaling required the activation of SIRT1. Knockdown of SIRT1 resulted in the reversal of ISO beneficiary effects suggesting that the lipid-lowering activity of ISO was regulated by SIRT1 expression. To identify the direct target of ISO, limited proteolysis combined with mass spectrometry (LiP-SMap) strategy was applied and IQGAP2 was identified as the direct target for ISO in regulating lipid homeostasis. In the presence of ISO, both mRNA and protein levels of SIRT1 were increased; however, this effect was abolished by blocking IQGAP2 expression using siRNA. To explore how IQGAP2 regulated the expression level of SIRT1, proteome profiler human phospho-kinase array kit was used to reveal possible phosphorylated kinases and signaling nodes that ISO affected. We found that through phosphorylation of CREB, ISO transduced signals from IQGAP2 to upregulate SIRT1 expression. Thus, we not only demonstrated the molecular basis of ISO in regulating lipid metabolism but also exhibited for the first time a novel IQGAP2-CREB-SIRT1 axis in treating NAFLD/NASH.
Tan Diaoyi,Miao Daojia,Zhao Chuanyi,Shi Jian,Lv Qingyang,Lu Feiyi,Ruan Hailong,Xiong Zhiyong,Zhang Xiaoping
Aldehyde dehydrogenases superfamily (ALDHs), which are ubiquitously present in various organisms with diverse subcellular localizations, play a crucial role in regulating malignant tumor progression; Nevertheless, their involvement in clear cell renal cell carcinoma (ccRCC) has not been elucidated. In this study, we performed comprehensive bioinformatics analyses on the 19 ALDHs genes, and identified ALDH9A1 as a key contributor in ccRCC. Expression patterns and clinical relevance of ALDH9A1 were determined using bioinformatics analyses, real-time PCR, western blotting, and immunohistochemistry. To explore the underlying mechanism behind the tumor suppressor role of ALDH9A1, RNA sequencing, methylated RNA immunoprecipitation, luciferase reporter assay, mass spectroscopy, immunoprecipitation, mutational studies and immunofluorescence were employed. The impact of ALDH9A1 in ccRCC progression and metabolic programming was assessed through both in vitro and in vivo. Here, this study revealed ALDH9A1 as a tumor suppressor gene in ccRCC. The fat mass and obesity associated protein (FTO) was identified as a demethylase for ALDH9A1 mRNA, resulting in its reduced stability and expression levels in ccRCC. Functional experiments demonstrated that the deficiency of ALDH9A1 in ccRCC promoted tumor proliferation, invasion, migration and lipid accumulation. Mechanistic insights illustrated that the diminished levels of ALDH9A1 resulted in the failure to sequester nucleophosmin 1 (NPM1) within cytoplasm, thereby suppressing the transcription of IQ motif containing the GTPase-activating protein 2 (IQGAP2), subsequently activating the AKT-mTOR signaling, ultimately fostering tumor progression and lipid accumulation. In conclusion, the present study highlights the robust prognostic significance of ALDH9A1 and delivers a comprehensive understanding of ALDH9A1-NPM1-IQGAP2-AKT axis in ccRCC. These findings established a solid research foundation for novel therapeutic strategies for ccRCC patients.
危险品化学品经营许可证（带存储）