title: Expression and signaling of the tyrosine kinase FGFR2b/KGFR regulates phagocytosis and melanosome uptake in human keratinocytes.
abstract: Membrane and actin cytoskeleton dynamics during phagocytosis can be triggered and amplified by the signal transduction of receptor tyrosine kinases. The epidermal keratinocytes appear to use the phagocytic mechanism of uptake to ingest melanosomes released by the melanocytes and play a pivotal role in the transfer process. We have previously demonstrated that the keratinocyte growth factor KGF/FGF7 promotes the melanosome uptake through activation of its receptor tyrosine kinase FGFR2b/KGFR. The aim of the present study was to investigate the contribution of KGFR expression, activation, and signaling in regulating the phagocytic process and the melanosome transfer. Phagocytosis was analyzed in vitro using fluorescent latex beads on human keratinocytes induced to differentiate. Melanosome transfer was investigated in keratinocyte-melanocyte cocultures. KGFR depletion by small interfering RNA microinjection and overexpression by transfection of wild type or defective mutant KGFR were performed to demonstrate the direct effect of the receptor on phagocytosis and melanosome transfer. Colocalization of the phagocytosed beads with the internalized receptors in phagolysosomes was analyzed by optical sectioning and 3-dimensional reconstruction. KGFR ligands triggered phagocytosis and melanosome transfer in differentiated keratinocytes, and receptor kinase activity and signaling were required for these effects, suggesting that FGFR2b/KGFR expression/activity and PLCγ signaling pathway play crucial roles in phagocytosis.
authors.affiliation: Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Medicina Clinica e Molecolare, Sapienza Università di Roma, Rome, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Belleudi
authors.forename: Valeria
authors.initials: V
authors.lastname: Purpura
authors.forename: Cristina
authors.initials: C
authors.lastname: Scrofani
authors.forename: Flavia
authors.initials: F
authors.lastname: Persechino
authors.forename: Laura
authors.initials: L
authors.lastname: Leone
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Torrisi
mesh_terms: D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D051526:Fibroblast Growth Factor 10 / Q000378:metabolism / Q000494:pharmacology; D051523:Fibroblast Growth Factor 7 / Q000378:metabolism / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020460:Melanosomes / Q000378:metabolism*; D008863:Microspheres; D009154:Mutation; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology*; D051966:Phospholipase C gamma / Q000378:metabolism; D011485:Protein Binding; D034622:RNA Interference; D051497:Receptor, Fibroblast Growth Factor, Type 2 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D051526:Fibroblast Growth Factor 10; D051523:Fibroblast Growth Factor 7; D051497:Receptor, Fibroblast Growth Factor, Type 2; C065104:keratinocyte growth factor receptor; D051966:Phospholipase C gamma