The endocytic pathway followed by the keratinocyte growth factor receptor.
Keratinocyte growth factor (KGF/FGF7) acts specifically on epithelial cells and regulates their proliferation and differentiation. It binds to and activates a receptor tyrosine kinase, the KGF receptor (KGFR), which is a splicing variant of the fibroblast growth factor receptor 2. The endocytic pathway followed by KGF and its receptor was analyzed here using immunofluorescence and confocal microscopy. After 10 min of internalization at 37 degrees C, both KGF and its receptor were localized in early endosomes, and after 30-60 min of endocytosis ligand and receptor were seen to reach perinuclear late endosomes and not the recycling endosomal compartment. Parallel western blot analysis revealed that KGFRs were tyrosine phosphorylated both at early and late steps of internalization, suggesting that KGF and KGFR remain associated in active complexes through the endocytic pathway. Pulse-chase experiments showed that the internalized KGFRs underwent degradation detectable at 1 h of endocytosis at 37 degrees C, indicating that KGFRs are functionally downregulated.
Dipartimento di Medicina Sperimentale e Patologia, Università di Roma La Sapienza, Viale Regina Elena 324, 00161 Rome, Italy.
Francesca
F
Belleudi
Mara
M
Ceridono
Alessandro
A
Capone
Annalucia
A
Serafino
Cinzia
C
Marchese
Mauro
M
Picardo
Luigi
L
Frati
Maria Rosaria
MR
Torrisi
D016475:3T3 Cells; D000818:Animals; D015536:Down-Regulation; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D051379:Mice; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D021381:Protein Transport; D051497:Receptor, Fibroblast Growth Factor, Type 2; D017468:Receptors, Fibroblast Growth Factor / Q000378:metabolism*
C496453:FGF7 protein, human; C496454:Fgf7 protein, mouse; D017468:Receptors, Fibroblast Growth Factor; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors; D051497:Receptor, Fibroblast Growth Factor, Type 2; C065104:keratinocyte growth factor receptor