Kanai M, Göke M, Tsunekawa S, Podolsky D K
Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
J Biol Chem. 1997 Mar 7;272(10):6621-8. doi: 10.1074/jbc.272.10.6621.
Stimulation of fibroblast growth factor receptor 3 (FGFR3) results in a variety of functional effects, including regulation of epithelial cell growth and differentiation. In order to characterize the signaling pathway through which FGFR3 regulates cell growth, L6 cells lacking any endogenous FGFR were stably transfected with the two different human isoforms, FGFR3 IIIb and FGFR3 IIIc, that result from alternative splicing of exon III of the FGFR3 gene encoding the ligand binding domain. Expression of FGFR3 IIIc in stably transfected L6 cells conferred growth responses to several members of the FGF family including FGF-1, -2, -4, and -6, while FGFR3 IIIb-expressing cells responded only to FGF-1. Activation of FGFR3 upon ligand binding resulted in activation of mitogen-activated protein kinase pathway. FGFR3 utilizes two different pools of adapter protein GRB2 to link to Ras. Activated FGFR3 predominantly interacts with GRB2.Sos in complex with a previously identified 90-kDa protein and designated protein 80K-H. In addition, 80K-H.GRB2. Sos complex was found to contain a novel 66-kDa protein. Tyrosine phophorylation of the 66-kDa protein was dependent on ligand activation of FGFR3, suggesting that the 66-kDa protein may play an important role in FGFR3-specific signaling. In addition to this unique pathway, FGFR3 also links to GRB2.Sos complex via the adapter protein Shc. Furthermore, activated FGFR3 was not able to induce dissociation of GRB2.Sos complex following Sos phosphorylation. In summary, FGFR3 signaling pathway utilizes two GRB2-containing complexes; Shc.GRB2.Sos and 80K-H.pp66.GRB2.Sos; these two complexes may alternatively link FGFG3 to mitogen-activated protein kinase. Finally, activated FGFR3 was also found to result in phosphorylation of phospholipase C-gamma but reduced phosphorylation of c-Src.
成纤维细胞生长因子受体3（FGFR3）的激活会产生多种功能效应，包括调节上皮细胞的生长和分化。为了阐明FGFR3调节细胞生长的信号通路，将缺乏内源性FGFR的L6细胞用两种不同的人异构体FGFR3 IIIb和FGFR3 IIIc进行稳定转染，这两种异构体是由编码配体结合域的FGFR3基因外显子III的可变剪接产生的。FGFR3 IIIc在稳定转染的L6细胞中的表达赋予了对FGF家族的几个成员（包括FGF-1、-2、-4和-6）的生长反应，而表达FGFR3 IIIb的细胞仅对FGF-1有反应。配体结合后FGFR3的激活导致丝裂原活化蛋白激酶途径的激活。FGFR3利用两种不同的衔接蛋白GRB2池与Ras相连。活化的FGFR3主要与与先前鉴定的90 kDa蛋白形成复合物的GRB2.Sos相互作用，并将其命名为蛋白80K-H。此外，发现80K-H.GRB2.Sos复合物含有一种新的66 kDa蛋白。66 kDa蛋白的酪氨酸磷酸化依赖于FGFR3的配体激活，这表明66 kDa蛋白可能在FGFR3特异性信号传导中起重要作用。除了这条独特的途径外，FGFR3还通过衔接蛋白Shc与GRB2.Sos复合物相连。此外，活化的FGFR3在Sos磷酸化后不能诱导GRB2.Sos复合物的解离。总之，FGFR3信号通路利用两种含GRB2的复合物；Shc.GRB2.Sos和80K-H.pp66.GRB2.Sos；这两种复合物可能将FGFG3与丝裂原活化蛋白激酶交替连接。最后，还发现活化的FGFR3会导致磷脂酶C-γ的磷酸化，但会降低c-Src的磷酸化。
