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ID 11762
Eprint ID
11762
FullText URL
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Title Alternative
変異FGFR3の恒常的リン酸化は先天性小人症の重要な因子でPLCγによるSTAT1の活性化を介して軟骨前駆細胞ATDC5のアポトーシスを誘導する
Author
Harada, Daisuke
Abstract
The most frequent type of rhizomelic dwarfism, achondroplasia (ACH), is caused by mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. Mutations in FGFR3 result in skeletal dysplasias of variable severity, including mild phenotypic effects in hypochondroplasia (HCH), severe phenotypic effects in thanatophoric dysplasia types I (TDI) and II (TDII), and severe but survivable phenotypic effects in severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN). To explore the molecular mechanisms that result in the different phenotypes, we investigated the kinetics of mutated versions of FGFR3. First, we assayed the phosphorylation states of the mutated FGFR3s and found that the level of phosphorylation in TDI-FGFR3 was lower than in ACH-FGFR3, although the other mutants were phosphorylated according to phenotypic severity. Second, we analyzed the duration of the phosphorylation. TDI-FGFR3 was not highly phosphorylated under ligand-free conditions, but the peak phosphorylation levels of TDI-FGFR3 and ACH-FGFR3 were maintained for 30 min after stimulation with FGF-1. Moreover, ligand-dependent phosphorylation of TDI-FGFR3, but not ACH-FGFR3, lasted for more than 8 h after FGF-1 administration. The other mutant proteins showed sustained phosphorylation independent of ligand presence. Third, we investigated the intracellular localization of the mutant proteins. Immunofluorescence analysis showed accumulations of TDII-FGFR3, SADDAN-FGFR3, and a portion of TDI-FGFR3 in the endoplasmic reticulum (ER). Based on these data, we concluded that sustained phosphorylation of FGFR3 causes chondrodysplasia, and the phenotypic severity depends on the proportion of ER-localized mutant FGFR3. In FGFR3 signaling, the transcription factor, signal transducer and activator of transcription 1 (STAT1) inhibit proliferation and induce apoptosis of chondrocytes. Here we reveal that phospholipase C gamma (PLCgamma) mediates FGFR3-induced STAT1 activation. Both PLCgamma and STAT1 were activated by FGFR3 signaling, but a dominant-negative form of PLCgamma (DN-PLCgamma) remarkably reduced STAT1 phosphorylation. Apoptosis assays revealed that the constitutively active forms of FGFR3 (TDII-FGFR3) and STAT1 (STAT1-C) induce apoptosis of chondrogenic ATDC5 cells via caspase activity. DN-PLCgamma reduced the apoptosis of ATDC5 cells expressing TDII-FGFR3, but over-expression of both DN-PLCgamma and STAT1-C induced apoptosis. Therefore, we conclude that a PLCgamma-STAT1 pathway mediates apoptotic signaling by FGFR3.
Keywords
FGFR3
Skeletal dysplasia
Phosphorylation
ER localization
STAT1
Note
http://dx.doi.org/10.1016/j.bone.2006.11.030
Published Date
2007-03-23
Publication Title
Content Type
Thesis or Dissertation
Grant Number
甲第3325号
Granted Date
2007-03-23
Thesis Type
博士(医学)
Grantor
岡山大学
Official Url
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17561467&dopt=Abstract
language
日本語
File Version
none
Refereed
Unknown