Uptake and intracellular transport of acidic fibroblast growth factor: evidence for free and cytoskeleton-anchored fibroblast growth factor receptors

Endocytic uptake and intracellular transport of acidic FGF was studied in cells transfected with FGF receptor 4 (FGFR4). Acidification of the cytosol to block endocytic uptake from coated pits did not inhibit endocytosis of the growth factor in COS cells transfected with FGFR4, indicating that it is...

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Bibliographic Details
Published in:Molecular biology of the cell 1999-11, Vol.10 (11), p.3835-3848
Main Authors: Citores, L, Wesche, J, Kolpakova, E, Olsnes, S
Format: Article
Language:English
Subjects:
Animals
Biological Transport
Caveolin 1
Caveolins
Cell Line
Cross-Linking Reagents
Cytoskeleton - metabolism
Fibroblast Growth Factor 1 - metabolism
Fluorescent Antibody Technique
Humans
Iodine Radioisotopes
Membrane Proteins - metabolism
Nocodazole - pharmacology
Phosphotyrosine - analysis
Protein-Tyrosine Kinases - metabolism
Receptor, Fibroblast Growth Factor, Type 4
Receptors, Fibroblast Growth Factor - genetics
Succinimides - chemistry
Transfection
Transferrin - metabolism
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Summary:Endocytic uptake and intracellular transport of acidic FGF was studied in cells transfected with FGF receptor 4 (FGFR4). Acidification of the cytosol to block endocytic uptake from coated pits did not inhibit endocytosis of the growth factor in COS cells transfected with FGFR4, indicating that it is to a large extent taken up by an alternative endocytic pathway. Fractionation of the cells demonstrated that part of the growth factor receptor was present in a low-density, caveolin-containing fraction, but we were unable to demonstrate binding to caveolin in immunoprecipitation studies. Upon treatment of the cells with acidic FGF, the activated receptor, together with the growth factor, moved to a juxtanuclear compartment, which was identified as the recycling endosome compartment. When the cells were lysed with Triton X-100, 3-([3-chloramidopropyl]dimethylammonio)-2-hydroxy-1-propanesulfona te, or 2-octyl glucoside, almost all surface-exposed and endocytosed FGFR4 was solubilized, but only a minor fraction of the total FGFR4 in the cells was found in the soluble fraction. The data indicate that the major part of FGFR4 is anchored to detergent-insoluble structures, presumably cytoskeletal elements associated with the recycling endosome compartment.
ISSN:1059-1524
1939-4586
DOI:10.1091/mbc.10.11.3835