Adhesion G Protein-Coupled Receptor L4 (ADGRL4/ELTD1) is an endothelial cell adhesion G protein-coupled receptor (aGPCR) which regulates physiological and tumour angiogenesis, providing an attractive target for anti-cancer therapeutics. To date, ADGRL4/ELTD1's full role and mechanism of function within endothelial biology remains unknown, as do its ligand(s). In this study, ADGRL4/ELTD1 silencing, using two independent small interfering RNAs (siRNAs), was performed in human umbilical vein endothelial cells (HUVECS) followed by transcriptional profiling, target gene validation, and metabolomics using liquid chromatography-mass spectrometry in order to better characterise ADGRL4/ELTD1's role in endothelial cell biology. We show that ADGRL4/ELTD1 silencing induced expression of the cytoplasmic metabolic regulator ATP Citrate Lyase (ACLY) and the mitochondria-to-cytoplasm citrate transporter Solute Carrier Family 25 Member 1 (SLC25A1) but had no apparent effect on pathways downstream of ACLY (fatty acid and cholesterol synthesis or acetylation). Silencing induced KIT expression and affected the Notch signalling pathway, upregulating Delta Like Canonical Notch Ligand 4 (DLL4) and suppressing Jagged Canonical Notch Ligand 1 (JAG1) and Hes Family BHLH Transcription Factor 2 (HES2). The effect of ADGRL4/ELTD1 silencing on the cellular metabolic profile was modest but several metabolites were significantly affected. Cis-aconitic acid, uridine diphosphate (UDP)-glucoronate, fructose 2,6-diphosphate, uridine 5-diphosphate, and aspartic acid were all elevated as a result of silencing and phosphocreatine, N-acetylglutamic acid, taurine, deoxyadenosine triphosphate, and cytidine monophosphate were depleted. Metabolic pathway analysis implicated ADGRL4/ELTD1 in pyrimidine, amino acid, and sugar metabolism. In summary, this study shows that ADGRL4/ELTD1 impacts core components of endothelial metabolism and regulates genes involved in endothelial differentiation/homeostasis and Notch signalling.

中文翻译：

---

内皮细胞中的 ADGRL4/ELTD1 沉默会诱导 ACLY 和 SLC25A1 并改变细胞代谢特征。


粘附 G 蛋白偶联受体 L4 (ADGRL4/ELTD1) 是一种内皮细胞粘附 G 蛋白偶联受体 (aGPCR)，可调节生理和肿瘤血管生成，为抗癌治疗提供了一个有吸引力的靶点。迄今为止，ADGRL4/ELTD1 在内皮生物学中的完整作用和功能机制仍然未知，其配体也是如此。在本研究中，使用两个独立的小干扰 RNA (siRNA) 在人脐静脉内皮细胞 (HUVECS) 中进行 ADGRL4/ELTD1 沉默，然后使用液相色谱-质谱法进行转录分析、靶基因验证和代谢组学，以便更好地表征 ADGRL4/ELTD1 在内皮细胞生物学中的作用。我们发现 ADGRL4/ELTD1 沉默诱导细胞质代谢调节剂 ATP 柠檬酸裂解酶 (ACLY) 和线粒体到细胞质柠檬酸转运蛋白溶质载体家族 25 成员 1 (SLC25A1) 的表达，但对 ACLY 下游途径没有明显影响（脂肪酸和胆固醇合成或乙酰化）。沉默诱导 KIT 表达并影响 Notch 信号通路，上调 Delta Like Canonical Notch Ligand 4 (DLL4) 并抑制锯齿状 Canonical Notch Ligand 1 (JAG1) 和 Hes Family BHLH 转录因子 2 (HES2)。 ADGRL4/ELTD1 沉默对细胞代谢谱的影响不大，但几种代谢物受到显着影响。顺式乌头酸、尿苷二磷酸 (UDP)-葡萄糖醛酸、果糖 2,6-二磷酸、尿苷 5-二磷酸和天冬氨酸均因沉默而升高，磷酸肌酸、N-乙酰谷氨酸、牛磺酸、脱氧腺苷三磷酸和单磷酸胞苷已耗尽。 代谢途径分析表明 ADGRL4/ELTD1 参与嘧啶、氨基酸和糖代谢。总之，本研究表明 ADGRL4/ELTD1 影响内皮代谢的核心成分，并调节参与内皮分化/稳态和 Notch 信号传导的基因。