Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, 53201, USA.
Department of Biology, Northeastern Illinois University, Chicago, IL, 60625, USA.
Dev Biol. 2024 Dec;516:183-195. doi: 10.1016/j.ydbio.2024.08.014. Epub 2024 Aug 21.
Fibroblast Growth Factors and their receptors (FGFRs) comprise a cell signaling module that can stimulate signaling by Ras and the kinases Raf, MEK, and ERK to regulate animal development and homeostatic functions. In Caenorhabditis elegans, the sole FGFR ortholog EGL-15 acts with the GRB2 ortholog SEM-5 to promote chemoattraction and migration by the sex myoblasts (SMs) and fluid homeostasis by the hypodermis (Hyp7). Cell-specific differences in EGL-15 signaling were suggested by the phenotypes caused by egl-15(n1457), an allele that removes a region of its C-terminal domain (CTD) known to bind SEM-5. To determine how mutations altered EGL-15 activity in the SMs and Hyp7, we used the kinase reporter ERK-KTR to measure activation of the ERK ortholog MPK-1. Consequences of egl-15(n1457) were cell-specific, resulting in loss of MPK-1 activity in the SMs and elevated activity in Hyp7. Previous studies of Hyp7 showed that loss of the CLR-1 phosphatase causes a fluid homeostasis defect termed "Clear" that is suppressed by reduction of EGL-15 signaling, a phenotype termed "Suppressor of Clear" (Soc). To identify mechanisms that permit EGL-15 signaling in Hyp7, we conducted a genetic screen for Soc mutants in the clr-1; egl-15(n1457) genotype. We report the identification of SOC-3, a protein with putative SEM-5-binding motifs and PH and PTB domains similar to DOK and IRS proteins. In combination with the egl-15(n1457) mutation, loss of either soc-3, the GAB1 ortholog soc-1, or the SHP2 ortholog ptp-2, reduced MPK-1 activation. We generated alleles of soc-3 to test the requirement for the SEM-5-binding motifs, finding that residue Tyr is required for function. We propose that EGL-15-mediated SM chemoattraction relies solely on the direct interaction between SEM-5 and the EGL-15 CTD. In Hyp7, EGL-15 signaling uses two mechanisms: the direct SEM-5 binding mechanism; and an alternative, CTD-independent mechanism involving SOC-3, SOC-1, and PTP-2. This work demonstrates that FGF signaling uses distinct, tissue-specific mechanisms in development, and identifies SOC-3 as a potential adaptor that facilitates Ras pathway activation by FGFR.
成纤维细胞生长因子及其受体(FGFRs)构成了一个细胞信号模块,可以刺激 Ras 和激酶 Raf、MEK 和 ERK 的信号转导,从而调节动物的发育和体内平衡功能。在秀丽隐杆线虫中,唯一的 FGFR 直系同源物 EGL-15 与 GRB2 直系同源物 SEM-5 一起作用,促进性肌肉母细胞(SMs)的趋化性和迁移以及真皮(Hyp7)的体液稳态。由 egl-15(n1457)引起的表型表明 EGL-15 信号存在细胞特异性差异,该等位基因去除了其 C 末端结构域(CTD)的一个区域,该区域已知与 SEM-5 结合。为了确定突变如何改变 SMs 和 Hyp7 中的 EGL-15 活性,我们使用激酶报告 ERK-KTR 来测量 ERK 直系同源物 MPK-1 的激活。egl-15(n1457)的后果是细胞特异性的,导致 SMs 中 MPK-1 活性丧失和 Hyp7 中活性升高。以前对 Hyp7 的研究表明,CLR-1 磷酸酶的缺失会导致一种称为“Clear”的体液稳态缺陷,该缺陷被 EGL-15 信号的降低所抑制,这种表型称为“Clear 的抑制物”(Soc)。为了确定允许 EGL-15 在 Hyp7 中信号转导的机制,我们在 clr-1;egl-15(n1457)基因型中进行了 Soc 突变的遗传筛选。我们报告了 SOC-3 的鉴定,SOC-3 是一种具有假定的 SEM-5 结合基序和 PH 和 PTB 结构域的蛋白质,类似于 DOK 和 IRS 蛋白。与 egl-15(n1457)突变结合,soc-3、GAB1 直系同源物 soc-1 或 SHP2 直系同源物 ptp-2 的缺失均降低了 MPK-1 的激活。我们生成了 soc-3 的等位基因来测试 SEM-5 结合基序的要求,发现残基 Tyr 是功能所必需的。我们提出,EGL-15 介导的 SM 趋化性仅依赖于 SEM-5 和 EGL-15 CTD 之间的直接相互作用。在 Hyp7 中,EGL-15 信号转导使用两种机制:直接的 SEM-5 结合机制;和一种替代的、不依赖 CTD 的机制,涉及 SOC-3、SOC-1 和 PTP-2。这项工作表明,FGF 信号在发育过程中使用不同的、组织特异性的机制,并确定 SOC-3 是一种潜在的衔接蛋白,可通过 FGFR 促进 Ras 途径的激活。