title: Clathrin- and dynamin-independent endocytosis of FGFR3--implications for signalling.
abstract: Endocytosis of tyrosine kinase receptors can influence both the duration and the specificity of the signal emitted. We have investigated the mechanisms of internalization of fibroblast growth factor receptor 3 (FGFR3) and compared it to that of FGFR1 which is internalized predominantly through clathrin-mediated endocytosis. Interestingly, we observed that FGFR3 was internalized at a slower rate than FGFR1 indicating that it may use a different endocytic mechanism than FGFR1. Indeed, after depletion of cells for clathrin, internalization of FGFR3 was only partly inhibited while endocytosis of FGFR1 was almost completely abolished. Similarly, expression of dominant negative mutants of dynamin resulted in partial inhibition of the endocytosis of FGFR3 whereas internalization of FGFR1 was blocked. Interfering with proposed regulators of clathrin-independent endocytosis such as Arf6, flotillin 1 and 2 and Cdc42 did not affect the endocytosis of FGFR1 or FGFR3. Furthermore, depletion of clathrin decreased the degradation of FGFR1 resulting in sustained signalling. In the case of FGFR3, both the degradation and the signalling were only slightly affected by clathrin depletion. The data indicate that clathrin-mediated endocytosis is required for efficient internalization and downregulation of FGFR1 while FGFR3, however, is internalized by both clathrin-dependent and clathrin-independent mechanisms.
authors.affiliation: Centre for Cancer Biomedicine, Faculty Division Norwegian Radium Hospital, University of Oslo, Oslo, Norway.
authors.forename: Ellen Margrethe
authors.initials: EM
authors.lastname: Haugsten
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Zakrzewska
authors.forename: Andreas
authors.initials: A
authors.lastname: Brech
authors.forename: Sascha
authors.initials: S
authors.lastname: Pust
authors.forename: Sjur
authors.initials: S
authors.lastname: Olsnes
authors.forename: Kirsten
authors.initials: K
authors.lastname: Sandvig
authors.forename: Jørgen
authors.initials: J
authors.lastname: Wesche
mesh_terms: D015153:Blotting, Western; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics / Q000502:physiology; D002966:Clathrin / Q000235:genetics / Q000378:metabolism*; D034281:Dynamins / Q000235:genetics / Q000378:metabolism*; D004705:Endocytosis / Q000235:genetics / Q000502:physiology*; D006801:Humans; D018613:Microscopy, Confocal; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000235:genetics / Q000378:metabolism*; D051498:Receptor, Fibroblast Growth Factor, Type 3 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology
chemical_list: D002966:Clathrin; C496348:FGFR1 protein, human; D051496:Receptor, Fibroblast Growth Factor, Type 1; D051498:Receptor, Fibroblast Growth Factor, Type 3; D034281:Dynamins