Prostaglandins differently regulate FGF-2 and FGF receptor expression and induce nuclear translocation in osteoblasts via MAPK kinase.
We have previously reported that prostaglandin F(2alpha) (PGF(2alpha)) and its selective agonist fluprostenol increase basic fibroblast growth factor (FGF-2) mRNA and protein production in osteoblastic Py1a cells. The present report extends our previous studies by showing that Py1a cells express FGF receptor-2 (FGFR2) and that treatment with PGF(2alpha) or fluprostenol decreases FGFR2 mRNA. We have used confocal and electron microscopy to show that, under PGF(2alpha) stimulation, FGF-2 and FGFR2 proteins accumulate near the nuclear envelope and colocalize in the nucleus of Py1a cells. Pre-treatment with cycloheximide blocks nuclear labelling for FGF-2 in response to PGF(2alpha). Treatment with SU5402 does not block prostaglandin-mediated nuclear internalization of FGF-2 or FGFR2. Various effectors have been used to investigate the signal transduction pathway. In particular, pre-treatment with phorbol 12-myristate 13-acetate (PMA) prevents the nuclear accumulation of FGF-2 and FGFR2 in response to PGF(2alpha). Similar results are obtained by pre-treatment with the protein kinase C (PKC) inhibitor H-7. In addition, cells treated with PGF(2alpha) exhibit increased nuclear labelling for the mitogen-activated protein kinase (MAPK), p44/ERK2. Pre-treatment with PMA blocks prostaglandin-induced ERK2 nuclear labelling, as confirmed by Western blot analysis. We conclude that PGF(2alpha) stimulates nuclear translocation of FGF-2 and FGFR2 by a PKC-dependent pathway; we also suggest an involvement of MAPK/ERK2 in this process.
Sabbieti
Maria Giovanna
MG
Department of Comparative Morphology and Biochemistry, Via Gentile III da Varano, 62032 Camerino (MC), Italy. giovanna.sabbieti@unicam.it
Marchetti
Luigi
L
Gabrielli
Maria Gabriella
MG
Menghi
Maura
M
Materazzi
Stefano
S
Menghi
Giovanna
G
Raisz
Lawrence G
LG
Hurley
Marja M
MM
D000818:Animals; D015153:Blotting, Western; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D015237:Dinoprost / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation / Q000187:drug effects*; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009685:Nuclear Envelope / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D010006:Osteoblasts / Q000187:drug effects* / Q000201:enzymology* / Q000378:metabolism / Q000648:ultrastructure; D011453:Prostaglandins / Q000494:pharmacology*; D011461:Prostaglandins F, Synthetic / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D051497:Receptor, Fibroblast Growth Factor, Type 2; D017468:Receptors, Fibroblast Growth Factor / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure
D011453:Prostaglandins; D011461:Prostaglandins F, Synthetic; D012333:RNA, Messenger; D017468:Receptors, Fibroblast Growth Factor; D016222:Fibroblast Growth Factor 2; C006326:fluprostenol; D015237:Dinoprost; C496356:Fgfr2 protein, rat; D020794:Receptor Protein-Tyrosine Kinases; D051497:Receptor, Fibroblast Growth Factor, Type 2; D048052:Mitogen-Activated Protein Kinase 3