Berlin Institute of Health at Charité-Universitätsmedizin Berlin, BIH Biomedical Innovation Academy, D-10178 Berlin, Germany.
Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Nephrology and Medical Intensive Care, Campus Virchow Klinikum, D-13353 Berlin, Germany.
Int J Mol Sci. 2022 Apr 2;23(7):3984. doi: 10.3390/ijms23073984.
The angiotensin II (Ang II) type 1 receptor (ATR) is involved in the regulation of blood pressure (through vasoconstriction) and water and ion homeostasis (mediated by interaction with the endogenous agonist). ATR can also be activated by auto-antibodies (ATR-Abs), which are associated with manifold diseases, such as obliterative vasculopathy, preeclampsia and systemic sclerosis. Knowledge of the molecular mechanisms related to ATR-Abs binding and associated signaling cascade (dys-)regulation remains fragmentary. The goal of this study was, therefore, to investigate details of the effects of ATR-Abs on G-protein signaling and subsequent cell proliferation, as well as the putative contribution of the three extracellular receptor loops (ELs) to Abs-ATR signaling. ATR-Abs induced nuclear factor of activated T-cells (NFAT) signaling, which reflects G and G activation. The impact on cell proliferation was tested in different cell systems, as well as activation-triggered receptor internalization. Blockwise alanine substitutions were designed to potentially investigate the role of ELs in ATR-Abs-mediated effects. First, we demonstrate that Ang II-mediated internalization of ATR is impeded by binding of ATR-Abs. Secondly, exclusive ATR-Abs-induced G activation is most significant for NFAT stimulation and mediates cell proliferation. Interestingly, our studies also reveal that ligand-independent, baseline ATR activation of G signaling has, in turn, a negative effect on cell proliferation. Indeed, inhibition of G basal activity potentiates proliferation triggered by ATR-Abs. Finally, although ATR containing EL1 and EL3 blockwise alanine mutations were not expressed on the human embryonic kidney293T (HEK293T) cell surface, we at least confirmed that parts of EL2 are involved in interactions between ATR and Abs. This current study thus provides extended insights into the molecular action of ATR-Abs and associated mechanisms of interrelated pathogenesis.
血管紧张素 II（Ang II）1 型受体（ATR）参与血压调节（通过血管收缩）和水和离子稳态（通过与内源性激动剂相互作用介导）。ATR 也可以被自身抗体（ATR-Abs）激活，这些抗体与多种疾病有关，如闭塞性血管病、先兆子痫和系统性硬化症。与 ATR-Abs 结合和相关信号级联（功能障碍）调节相关的分子机制的知识仍然是零散的。因此，本研究的目的是研究 ATR-Abs 对 G 蛋白信号转导和随后的细胞增殖的影响的细节，以及三个细胞外受体环（EL）对 Abs-ATR 信号转导的潜在贡献。ATR-Abs 诱导核因子活化 T 细胞（NFAT）信号转导，反映 G 和 G 的激活。在不同的细胞系统中测试了对细胞增殖的影响，以及激活触发的受体内化。设计了分块的丙氨酸取代，以潜在地研究 EL 在 ATR-Abs 介导的作用中的作用。首先，我们证明 ATR-Abs 的结合阻碍了 Ang II 介导的 ATR 内化。其次，ATR-Abs 诱导的 G 激活是 NFAT 刺激和介导细胞增殖的最重要因素。有趣的是，我们的研究还表明，配体非依赖性的、基线 ATR 对 G 信号转导的激活反过来对细胞增殖有负面影响。事实上，抑制 G 的基础活性增强了 ATR-Abs 触发的增殖。最后，尽管含有 EL1 和 EL3 的 ATR 分块的丙氨酸突变体不能在人胚肾 293T（HEK293T）细胞表面表达，但我们至少证实了 EL2 的部分参与了 ATR 和 Abs 之间的相互作用。因此，本研究为 ATR-Abs 的分子作用及其相关发病机制的相互关联机制提供了扩展的见解。
