Department of Biomedical Sciences, Colorado State University, 1617 Campus Delivery, Fort Collins, CO, 80523, USA.
Cell Commun Signal. 2023 Oct 12;21(1):284. doi: 10.1186/s12964-023-01313-y.
Gonadotropin-releasing hormone (GnRH) receptors are essential for reproduction and are expressed in numerous urogenital, reproductive, and non-reproductive cancers. In addition to canonical G protein-coupled receptor signaling, GnRH receptors functionally interact with several receptor tyrosine kinases. AXL is a receptor tyrosine kinase expressed in numerous tissues as well as multiple tumors. Here we tested the hypothesis that AXL, along with its endogenous ligand Gas6, impacts GnRH receptor signaling.
We used clonal murine pituitary αT3-1 and LβT2 gonadotrope cell lines to examine the effect of AXL activation on GnRH receptor-dependent signaling outcomes. ELISA and immunofluorescence were used to observe AXL and GnRH receptor expression in αT3-1 and LβT2 cells, as well as in murine and human pituitary sections. We also used ELISA to measure changes in ERK phosphorylation, pro-MMP9 production, and release of LHβ. Digital droplet PCR was used to measure the abundance of Egr-1 transcripts. A transwell migration assay was used to measure αT3-1 and LβT2 migration responses to GnRH and AXL.
We observed AXL, along with the GnRH receptor, expression in αT3-1 and LβT2 gonadotrope cell lines, as well as in murine and human pituitary sections. Consistent with a potentiating role of AXL, Gas6 enhanced GnRH-dependent ERK phosphorylation in αT3-1 and LβT2 cells. Further, and consistent with enhanced post-transcriptional GnRH receptor responses, we found that Gas6 increased the abundance of Egr-1 transcripts. Suggesting functional significance, in LβT2 cells, Gas6/AXL signaling stimulated LHβ production and enhanced GnRH receptor-dependent generation of pro-MMP9 protein and promoted cell migration.
Altogether, these data describe a novel role for AXL as a modulator of GnRH receptor signaling. Video Abstract.
促性腺激素释放激素（GnRH）受体对于生殖至关重要，并且在许多泌尿生殖、生殖和非生殖性癌症中表达。除了经典的 G 蛋白偶联受体信号转导外，GnRH 受体还与几种受体酪氨酸激酶具有功能相互作用。AXL 是一种在许多组织以及多种肿瘤中表达的受体酪氨酸激酶。在这里，我们检验了这样一个假设，即 AXL 及其内源性配体 Gas6 会影响 GnRH 受体信号。
我们使用克隆的鼠垂体αT3-1 和 LβT2 促性腺激素细胞系来研究 AXL 激活对 GnRH 受体依赖性信号转导结果的影响。ELISA 和免疫荧光用于观察αT3-1 和 LβT2 细胞以及鼠和人垂体切片中 AXL 和 GnRH 受体的表达。我们还使用 ELISA 测量 ERK 磷酸化、pro-MMP9 产生和 LHβ 的释放变化。数字液滴 PCR 用于测量 Egr-1 转录物的丰度。使用 Transwell 迁移测定法测量αT3-1 和 LβT2 对 GnRH 和 AXL 的迁移反应。
我们观察到 AXL 与 GnRH 受体一起在αT3-1 和 LβT2 促性腺激素细胞系以及鼠和人垂体切片中表达。与 AXL 具有增强作用一致，Gas6 增强了αT3-1 和 LβT2 细胞中 GnRH 依赖性 ERK 磷酸化。进一步，与增强的 GnRH 受体转录后反应一致，我们发现 Gas6 增加了 Egr-1 转录物的丰度。提示功能意义，在 LβT2 细胞中，Gas6/AXL 信号刺激 LHβ 的产生，并增强 GnRH 受体依赖性 pro-MMP9 蛋白的产生，并促进细胞迁移。
总之，这些数据描述了 AXL 作为 GnRH 受体信号转导调节剂的新作用。
