ABSTRACT
Anosmin-1 is a secreted glycoprotein encoded by the ANOS1 gene, and its loss of function causes Kallmann syndrome (KS), which is characterized by anosmia and hypogonadism due to olfactory bulb (OB) dysfunction. However, the physiological function of anosmin-1 remains to be elucidated. In KS, disordered angiogenesis is observed in OB, resulting in its hypoplasia. In this study, we examined the involvement of anosmin-1 in angiogenic processes. Anosmin-1 was detected on the vessel-like structure in OB of chick embryos, and promoted the outgrowth of vascular sprouts as shown by assays of OB tissue culture. Cell migration, proliferation, and tube formation of endothelial cells were induced by treatment with anosmin-1 as well as vascular endothelial growth factor-A (VEGF-A), and further enhanced by treatment with both of them. We newly identified that anosmin-1 activated VEGF receptor-2 (VEGFR2) by binding directly to it, and its downstream signaling molecules, phospholipase Cγ1 (PLCγ1) and protein kinase C (PKC). These results suggest that anosmin-1 plays a key role in the angiogenesis of developing OB through the VEGFR2-PLCγ1-PKC axis by enhancing the VEGF function.
Subject(s)
Endothelium, Vascular/cytology , Extracellular Matrix Proteins/metabolism , Neovascularization, Physiologic , Nerve Tissue Proteins/metabolism , Olfactory Bulb/blood supply , Receptors, Vascular Endothelial Growth Factor/metabolism , Vascular Endothelial Growth Factor A/metabolism , Animals , Cell Movement , Cell Proliferation , Cells, Cultured , Chick Embryo , Extracellular Matrix Proteins/genetics , Humans , Morphogenesis , Nerve Tissue Proteins/genetics , Olfactory Bulb/cytology , Olfactory Bulb/metabolism , Receptors, Vascular Endothelial Growth Factor/genetics , Signal Transduction , Vascular Endothelial Growth Factor A/geneticsABSTRACT
Vascular endothelial growth factors (VEGFs) include five molecules (VEGF-A, -B, -C, -D, and placental growth factor), and have various roles that crucially regulate cellular functions in many kinds of cells and tissues. Intracellular signal transduction induced by VEGFs has been extensively studied and is usually initiated by their binding to two classes of transmembrane receptors: receptor tyrosine kinase VEGF receptors (VEGF receptor-1, -2 and -3) and neuropilins (NRP1 and NRP2). In addition to many established results reported by other research groups, we have previously identified small G proteins, especially Ras homologue gene (Rho) and Ras-related protein (Rap), as important mediators of VEGF-A-stimulated signaling in cancer cells as well as endothelial cells. This review article describes the VEGF-A-induced signaling pathways underlying diverse cellular functions, including cell proliferation, migration, and angiogenesis, and the involvement of Rho, Rap, and their related molecules in these pathways.
Subject(s)
Vascular Endothelial Growth Factor A/metabolism , rap GTP-Binding Proteins/metabolism , rho GTP-Binding Proteins/metabolism , Animals , Humans , Models, Biological , Neovascularization, Physiologic , Vascular Endothelial Growth Factor Receptor-2/metabolismABSTRACT
Heterozygous loss-of-function mutations of FGFR1 (fibroblast growth factor receptor 1) cause various disorders including hypogonadotropic hypogonadism with split-hand/foot malformation (HH-SHFM). We examined FGFR1 in four Japanese patients with HH-SHFM (cases 1-4) and the mother of case 4 with HH only. Cases 1 and 2 had heterozygous loss-of-function mutations with no dominant negative effect (c.289G>A, p.[G97S]; and c.2231G>C, p.[R744T]), and case 3 had a splice donor site mutation (c.1663+1G>T). Notably, case 4 had a maternally inherited 8,312 bp microdeletion that involved noncoding exon 1U and impaired FGFR1 expression. Furthermore, consistent with the presence of transcription-related histone marks (e.g., H3K4Me3, H3K4Me1, and H3K27Ac) and multiple transcription factor-binding sites around exon 1U, functional studies demonstrated a marked transactivation function of a 414-bp segment harboring the transcription start site. These results support the relevance of FGFR1 mutations to HH-SHFM, and argue for the presence of the FGFR1 core-promoter elements around exon 1U.
Subject(s)
Hypogonadism/diagnosis , Hypogonadism/genetics , Limb Deformities, Congenital/diagnosis , Limb Deformities, Congenital/genetics , Mutation , Receptor, Fibroblast Growth Factor, Type 1/genetics , Adolescent , Adult , Biomarkers , Female , Genetic Association Studies , Genotype , Humans , Infant , Male , Phenotype , Promoter Regions, Genetic , Sequence Analysis, DNA , SyndromeABSTRACT
We have previously cloned the alternatively spliced isoform of fibroblast growth factor receptor 3 (FGFR3DeltaAB) that lacks the acid box in the extracellular region. To understand the biological functions and signal transduction of these FGFR3 isoforms, we analyzed the effect of FGF1 in ATDC5 cells, chondroprogenitor cell lines overexpressing these isoforms. In response to FGF1, FGFR3 induced a marked cell-morphology change to a round shape, while FGFR3DeltaAB did not. Furthermore, FGFR3 induced complete growth arrest, whereas FGFR3DeltaAB induced only moderate growth inhibition. Both receptors induced the expression of the CDK inhibitor p21(CIP1). However, only FGFR3 induced STAT1 phosphorylation that mediates the transcriptional induction of p21(CIP1), although both FGFR3 isoforms could induce a strong activation of mitogen-activated protein (MAP) kinases. Taken together, the different biological responses mediated by FGFR3 and FGFR3DeltaAB appear to be due to a difference in their ability to utilize STAT1 pathway and signals involved in cell rounding.
