Evolutionarily conserved and divergent expression of members of the FGF receptor family among vertebrate embryos, as revealed by FGFR expression patterns in Xenopus

Fibroblast growth factors (FGFs) mediate many cell-cell signaling events during early development. While the actions of FGFs have been well-studied, the roles played by specific members of the FGF receptor (FGFR) family are poorly understood. To characterize the roles played by individual FGFRs we compared the regulation and expression of the three Xenopus FGFRs described to date (XFGFR-1, XFGFR-2, and XFGFR-4). First, we describe the expression of Xenopus FGFR-4; XFGFR-4 is present as a maternal mRNA and is found in the embryo through at least the tadpole stage. XFGFR-4 and XFGFR-1 mRNAs are present at comparable levels, arguing that both mediate FGF signaling during early development. Second, the expression of XFGFR-4 in animal caps differs from the expression of XFGFR-1 and XFGFR-2, suggesting that the FGFRs are independently regulated in ectoderm. Third, using whole-mount in situ hybridization, we show that XFGFR-1, XFGFR-2, and XFGFR-4 are expressed in dramatically different patterns, arguing that specific FGF signaling events are mediated by different members of the FGFR family. Among these, FGF signaling during the induction of neural crest cells is likely to be mediated by XFGFR-4. Comparison of our results with previously reported FGFR expression patterns reveals that FGFR-1 expression is highly conserved among vertebrate embryos, and FGFR-2 expression shows many features that are conserved and some that are divergent. In contrast, the expression pattern of FGFR-4 is highly divergent among vertebrate embryos. Received: 5 August 1999 / Accepted: 18 January 2000     

bFGF promotes adipocyte differentiation in human mesenchymal stem cells derived from embryonic stem cells

In this work we describe the establishment of mesenchymal stem cells (MSCs) derived from embryonic stem cells (ESCs) and the role of bFGF in adipocyte differentiation. The totipotency of ESCs and MSCs was assessed by immunofluorescence staining and RT-PCR of totipotency factors. MSCs were successfully used to induce osteoblasts, chondrocytes and adipocytes. MSCs that differentiated into adipocytes were stimulated with and without bFGF. The OD/DNA (optical density/content of total DNA) and expression levels of the specific adipocyte genes PPARγ2 (peroxisome proliferator activated receptor γ2) and C/EBPs were higher in bFGF cells. Embryonic bodies had a higher adipocyte level compared with cells cultured in plates. These findings indicate that bFGF promotes adipocyte differentiation. MSCs may be useful cells for seeding in tissue engineering and have enormous therapeutic potential for adipose tissue engineering.     

Identification of a crucial amino acid responsible for the loss of specifying FGFR1–KLB affinity of the iodinated FGF21

Previous studies suggest that specific binding to the complex consisting of fibroblast growth factor receptor-1 (FGFR1) and the coreceptor beta-Klotho (KLB) is the premise for human FGF19 and FGF21 activating the downstream signaling cascades, and regulating the metabolic homeostasis. However, it was found that human FGF21 loses its ability to bind to FGFR1–KLB after iodination with Na¹²⁵I and chloramine T, whereas human FGF19 retained its affinity for FGFR1–KLB even after iodination. The molecular mechanisms underlying these differences remained elusive. In this study, we first demonstrated that an intramolecular disulfide bond was formed between cysteine-102 and cysteine-121 in FGF21, implying that the oxidation of the cysteine to cysteic acid, which may interfere with the active conformation of FGF21, did not occur during the iodination procedures, and thus ruled out the possibility of the two conserved cysteine residues mediating the loss of FGF21 binding affinity to FGFR1–KLB upon iodination. Site-directed mutagenesis and molecular modeling were further applied to determine the residue(s) responsible for the loss of FGFR1–KLB affinity. The results showed that mutation of a single tyrosine-207, but not the other five tyrosine residues in FGF21, to a phenylalanine retained the FGFR1–KLB affinity of FGF21 even after iodination, whereas replacing the corresponding phenylalanine residue with tyrosine in FGF19 did not alter its binding affinity to FGFR1–KLB, but decreased the receptor binding ability of the iodinated protein, suggesting that tyrosine-207 is the crucial amino acid responsible for the loss of specifying FGFR1–KLB affinity of the iodinated FGF21.     

成纤维细胞生长因子的临床转化及相关新药研究进展

成纤维细胞生长因子;创伤修复;代谢调控;成纤维细胞生长因子受体抑制剂     

Autocrine activation of EGF receptor promotes oscillation of glutamate-induced calcium increase in astrocytes cultured in rat cerebral cortex

We previously reported that astrocytes cultured for more than 2 days in a defined medium containing epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) showed calcium oscillation in response to glutamate, whereas the response pattern was transient in the absence of the exogenous growth factors. In the present study, we found that astrocytes showed glutamate-induced calcium oscillation, even in growth factor-free medium, if the cells had been cultured for more than 5 days. The calcium oscillation promoted by the prolonged culture period was suppressed by an inhibitor of EGF receptor tyrosine kinase, but not by a neutralizing antibody to bFGF, indicating that the accumulation of an autocrine factor that activates the EGF receptor leads to calcium oscillation. Astrocytes in our culture system expressed EGF, transforming growth factor alpha (TGFalpha), bFGF and acidic fibroblast growth factor (aFGF). Exogenous aFGF, which induced astrocyte immediate early gene expression to the same extent as EGF or bFGF, did not affect calcium oscillation. Exogenous EGF and bFGF promoted astrocyte hypertrophic morphology and proliferation, as well as calcium oscillation. In contrast, these properties did not accompany calcium oscillation induced by the prolonged culture period. These results suggest that astrocytes possess the ability to promote their own calcium oscillation, which is independent of hypertrophic changes to reactive astrocytes.     

结肠癌细胞株和组织中EGFR、p-EGFR和p-IGFR-1β的表达及意义

目的：研究EGFR、p-EGFR和p-IGFR-1β在结肠癌细胞株的表达及其与吉非替尼敏感性的关系,以及在肿瘤组织中的表达状况、相关性及其与临床病理参数的关系。方法：以western blot检测EGFR、p-EGFR和p-IGFR-1β在结肠癌细胞株和组织中的表达,以Quantity One软件测量各蛋白条带的灰度值。结果：EGFR、p-EGFR在Lovo细胞中表达量最高（P〈0.05）,EGFR在SW620细胞中的表达最低（P〈0.05）,在HCT116、HT29、LS174T和SW480细胞中的表达差异不显著。p-IGFR-1β在Lovo、HT29和SW480细胞中表达较弱,且在Lovo细胞中表达更弱,但在HCT116、LS174T和SW620细胞中的表达均较强（P〈0.05）。结肠癌组织中EGFR表达率为55.6%（10/18）,癌旁正常组织为37.5%（3/18）,肿瘤组织中有表达增高的趋势;p-EGFR在结肠癌组织表达率为33.3%（6/18）,较正常组织的5.6%（1/18）明显增高（P〈0.05）;p-IGFR-1β在结肠癌组织表达率为44.4%（8/18）,较正常组织的11．1％（2／18）明显增高（P〈0．05）。EGFR、P-EGFR和P-IGFR-1β相互之间的表达无明显相关性;EGFR、P-EGFR表达与各临床病理参数无明显相关;P．IGFR-1β在淋巴结转移患者中的表达显著增高（P〈0．05）,且在分期晚的患者中也可观察到这种趋势。结论：结合我们以往的研究结果,P．EGFR表达高伴p-IGFR-1β表达低提示结肠癌细胞对吉非替尼的敏感性好。P-EGFR和P—IGFR-1β在结肠癌组织中的表达较正常组织明显增高,且p-IGFR．1B表达高可能预示结肠癌患者有较高的转移风险。     

改构酸性成纤维细胞生长因子对小鼠胸腺细胞凋亡的影响

目的:探讨改构酸性成纤维细胞生长因子(MaFGF)对地塞米松(DEX)诱导小鼠胸腺细胞凋亡的保护作用。方法:利用地塞米松诱导小鼠胸腺细胞凋亡的模型,将实验分为空白对照组、DEX处理组、aFGF+DEX组和MaFGF+DEX组,采用DNA琼脂糖凝胶电泳和流式细胞仪两种分析方法,测定MaFGF对小鼠胸腺细胞凋亡的影响。结果:空白对照组凋亡率为168%,DEX处理后小鼠胸腺细胞出现明显的细胞凋亡,凋亡率为196%,aFGF和MaFGF处理后的细胞凋亡受到抑制,凋亡率分别下降到1595%和1293%,MaFGF效应强于aFGF,且以剂量依赖方式发挥作用。结论:MaFGF具有以剂量依赖方式的胸腺细胞保护作用。     

Phospholipase Cγ Activation, Phosphotidylinositol Hydrolysis, and Calcium Mobilization are Not Required for FGF Receptor-Mediated Chemotaxis

Basic fibroblast growth factor (FGF) is a potent angiogenic factor that stimulates several cell types to migrate along a chemotactic gradient. Most chemoartractant receptors appear to share a common mechanism that involves activation of phospholipase C (PLC), hydrolysis of phosphotidylinositol, and mobilization of intracellular calcium. We transf ected two different cell lines with either human FGF receptor-1 cDNA or chimeric FGF receptor cDNA. Ligand stimulation induced chemotaxis, activation of PLOγ, phosphotidylinositol hydrolysis, and calcium mobilization in both wild-type receptor cell lines. No such response was elicited in control cells. Mutation of the two fibroblast growth factor receptors at residue 766, replacing tyrosine with phenylalanine, made the receptors incapable of associating with and activating PLCγ following ligand stimulation. These mutant receptors also failed to mediate phosphotidylinositol hydrolysis and calcium mobilization. However, cells transfected with the mutant fibroblast growth factor receptors were as chemotactically responsive to the appropriate ligand as were cells transfected with the wild-type receptors. These findings demonstrate that the ability of the fibroblast growth factor receptor to promote chemotaxis is not dependent on increased activation of PLCγ, increased hydrolysis of phosphotidylinositol, or increased global mobilization of calcium.     

Phospholipase Cγ Activation,Phosphotidylinositol Hydrolysis,and Calcium Mobilization are Not Required for FGF Receptor-Mediated Chemotaxis

Basic fibroblast growth factor (FGF) is a potent angiogenic factor that stimulates several cell types to migrate along a chemotactic gradient. Most chemoartractant receptors appear to share a common mechanism that involves activation of phospholipase C (PLC), hydrolysis of phosphotidylinositol, and mobilization of intracellular calcium. We transf ected two different cell lines with either human FGF receptor-1 cDNA or chimeric FGF receptor cDNA. Ligand stimulation induced chemotaxis, activation of PLOγ, phosphotidylinositol hydrolysis, and calcium mobilization in both wild-type receptor cell lines. No such response was elicited in control cells. Mutation of the two fibroblast growth factor receptors at residue 766, replacing tyrosine with phenylalanine, made the receptors incapable of associating with and activating PLCγ following ligand stimulation. These mutant receptors also failed to mediate phosphotidylinositol hydrolysis and calcium mobilization. However, cells transfected with the mutant fibroblast growth factor receptors were as chemotactically responsive to the appropriate ligand as were cells transfected with the wild-type receptors. These findings demonstrate that the ability of the fibroblast growth factor receptor to promote chemotaxis is not dependent on increased activation of PLCγ, increased hydrolysis of phosphotidylinositol, or increased global mobilization of calcium.     

噬菌体展示技术筛选bFGF模拟短肽

目的：通过噬菌体展示技术筛选得到与FGFR结合的bFGF模拟短肽,为bFGF肽类抑制剂的研发提供实验基础。方法：以Balb/c 3T3细胞为靶标,以COS-7细胞作消减,对噬菌体随机七肽库进行4轮生物淘洗,再采用ELISA检测单克隆噬菌体对Balb/c 3T3亲和性和特异性,选取阳性克隆进行DNA测序分析。结果：从富集的噬菌体中获得12个阳性克隆,获得一组疏水性七肽及共同基序PR。结论：利用肽类新药开发的重要工具--噬菌体展示技术,得到2段bFGF的受体结合模拟肽,可望作为bFGF抑制剂的先导肽。