title: Control of HIF-1{alpha} and vascular signaling in fetal lung involves cross talk between mTORC1 and the FGF-10/FGFR2b/Spry2 airway branching periodicity clock.
abstract: Lung development requires coordinated signaling between airway and vascular growth, but the link between these processes remains unclear. Mammalian target of rapamycin complex-1 (mTORC1) can amplify hypoxia-inducible factor-1α (HIF-1α) vasculogenic activity through an NH(2)-terminal mTOR binding (TOS) motif. We hypothesized that this mechanism coordinates vasculogenesis with the fibroblast growth factor (FGF)-10/FGF-receptor2b/Spry2 regulator of airway branching. First, we tested if the HIF-1α TOS motif participated in epithelial-mesenchymal vascular signaling. mTORC1 activation by insulin significantly amplified HIF-1α activity at fetal Po(2) (23 mmHg) in human bronchial epithelium (16HBE14o-) and induced vascular traits (Flk1, sprouting) in cocultured human embryonic lung mesenchyme (HEL-12469). This enhanced activation of HIF-1α by mTORC1 was abolished on expression of a HIF-1α (F99A) TOS-mutant and also suppressed vascular differentiation of HEL-12469 cocultures. Next, we determined if vasculogenesis in fetal lung involved regulation of mTORC1 by the FGF-10/FGFR2b/Spry2 pathway. Fetal airway epithelium displayed distinct mTORC1 activity in situ, and its hyperactivation by TSC1(-/-) knockout induced widespread VEGF expression and disaggregation of Tie2-positive vascular bundles. FGF-10-coated beads grafted into fetal lung explants from Tie2-LacZ transgenic mice induced localized vascular differentiation in the peripheral mesenchyme. In rat fetal distal lung epithelial (FDLE) cells cultured at fetal Po(2), FGF-10 induced mTORC1 and amplified HIF-1α activity and VEGF secretion without induction of ERK1/2. This was accompanied by the formation of a complex between Spry2, the cCBL ubiquitin ligase, and the mTOR repressor, TSC2, which abolished GTPase activity directed against Rheb, the G protein inducer of mTORC1. Thus, mTORC1 links HIF-1α-driven vasculogenesis with the FGF-10/FGFR2b/Spry2 airway branching periodicity regulator.
authors.affiliation: Centre for Cardiovascular and Lung Biology, Ninewells Hospital, Univ. of Dundee, Scotland, United Kingdom.
authors.forename: C L
authors.initials: CL
authors.lastname: Scott
authors.forename: D J
authors.initials: DJ
authors.lastname: Walker
authors.forename: E
authors.initials: E
authors.lastname: Cwiklinski
authors.forename: C
authors.initials: C
authors.lastname: Tait
authors.forename: A R
authors.initials: AR
authors.lastname: Tee
authors.forename: S C
authors.initials: SC
authors.lastname: Land
mesh_terms: D000818:Animals; D001683:Biological Clocks; D015153:Blotting, Western; D001980:Bronchi / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D002940:Circadian Rhythm; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism; D005333:Fetus / Q000166:cytology / Q000378:metabolism; D051526:Fibroblast Growth Factor 10 / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D008168:Lung / Q000166:cytology / Q000378:metabolism*; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism; D051379:Mice; D018919:Neovascularization, Physiologic; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D051497:Receptor, Fibroblast Growth Factor, Type 2 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D000077004:Tuberous Sclerosis Complex 1 Protein; D025521:Tumor Suppressor Proteins / Q000502:physiology
chemical_list: C519510:Crtc1 protein, rat; C496465:Fgf10 protein, rat; D051526:Fibroblast Growth Factor 10; C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; C404992:Spry2 protein, rat; C000624650:TSC1 protein, human; D014157:Transcription Factors; C000624651:Tsc1 protein, mouse; C000624652:Tsc1 protein, rat; D000077004:Tuberous Sclerosis Complex 1 Protein; D025521:Tumor Suppressor Proteins; D051497:Receptor, Fibroblast Growth Factor, Type 2