Lioubin M N, Myles G M, Carlberg K, Bowtell D, Rohrschneider L R
Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.
Mol Cell Biol. 1994 Sep;14(9):5682-91. doi: 10.1128/mcb.14.9.5682-5691.1994.
Fms, the macrophage colony-stimulating factor (M-CSF) receptor, is normally expressed in myeloid cells and initiates signals for both growth and development along the monocyte/macrophage lineage. We have examined Fms signal transduction pathways in the murine myeloid progenitor cell line FDC-P1. M-CSF stimulation of FDC-P1 cells expressing exogenous Fms resulted in tyrosine phosphorylation of a variety of cellular proteins in addition to Fms. M-CSF stimulation also resulted in Fms association with two of these tyrosine-phosphorylated proteins, one of which was identified as the 55-kDa Shc, which is shown in other systems to be involved in growth stimulation, and the other was a previously uncharacterized 150-kDa protein (p150). Fms also formed complexes with Grb2 and Sos1, and neither contained phosphotyrosine. Whereas both Grb2 and Sos1 complexed with Fms only after M-CSF stimulation, the amount of Sos1 complexed with Grb2 was not M-CSF dependent. Shc coimmunoprecipitated Sos1, Grb2, and tyrosine-phosphorylated p150, while Grb2 immunoprecipitates contained mainly phosphorylated p150, Fms, Shc, and Sos1. Shc interacted with tyrosine-phosphorylated p150 via its SH2 domain, and the Grb2 SH2 domain likewise bound tyrosine-phosphorylated Fms and p150. Analysis of Fms mutated at each of four tyrosine autophosphorylation sites indicated that none of these sites dramatically affected p150 phosphorylation or its association with Shc and Grb2. M-CSF stimulation of fibroblast cell lines expressing exogenous murine Fms did not phosphorylate p150, and this protein was not detected either in cell lysates or in Grb2 or Shc immunoprecipitates. The p150 protein is not related to known signal transduction molecules and may be myeloid cell specific. These results suggest that M-CSF stimulation of myeloid cells could activate Ras through the nucleotide exchange factor Sos1 by Grb2 binding to either Fms, Shc, or p150 and that Fms signal transduction in myeloid cells differs from that in fibroblasts.
Fms即巨噬细胞集落刺激因子（M-CSF）受体，通常在髓系细胞中表达，并启动单核细胞/巨噬细胞谱系生长和发育的信号。我们研究了小鼠髓系祖细胞系FDC-P1中的Fms信号转导途径。用M-CSF刺激表达外源性Fms的FDC-P1细胞，除Fms外，还导致多种细胞蛋白发生酪氨酸磷酸化。M-CSF刺激还导致Fms与其中两种酪氨酸磷酸化蛋白结合，其中一种被鉴定为55 kDa的Shc，在其他系统中显示其参与生长刺激，另一种是以前未鉴定的150 kDa蛋白（p150）。Fms还与Grb2和Sos1形成复合物，且两者均不含有磷酸酪氨酸。虽然Grb2和Sos1仅在M-CSF刺激后才与Fms形成复合物，但与Grb2结合的Sos1的量不依赖于M-CSF。Shc与Sos1、Grb2和酪氨酸磷酸化的p150共免疫沉淀，而Grb2免疫沉淀主要包含磷酸化的p150、Fms、Shc和Sos1。Shc通过其SH2结构域与酪氨酸磷酸化的p150相互作用，Grb2的SH2结构域同样结合酪氨酸磷酸化的Fms和p150。对四个酪氨酸自磷酸化位点各自发生突变的Fms进行分析表明，这些位点均未显著影响p150磷酸化或其与Shc和Grb2的结合。用M-CSF刺激表达外源性小鼠Fms的成纤维细胞系不会使p150磷酸化，并且在细胞裂解物或Grb2或Shc免疫沉淀中均未检测到该蛋白。p150蛋白与已知的信号转导分子无关，可能是髓系细胞特异性的。这些结果表明，M-CSF刺激髓系细胞可通过Grb2与Fms、Shc或p150结合，经核苷酸交换因子Sos1激活Ras，并且髓系细胞中的Fms信号转导不同于成纤维细胞中的。
