Cell Release of Bioactive Fibroblast Growth Factor 2 by Exon 6-encoded Sequence of Vascular Endothelial Growth Factor*
- Frédéric Jonca‡§¶‖,
- Nathalie Ortéga‡,
- Pierre-Emmanuel Gleizes‡,
- Nicolas Bertrandद and
- Jean Plouët‡**
- From the ‡Laboratoire de Biologie Moléculaire Eucaryote, CNRS UPR 9006, 118 Route de Narbonne, 31062, Toulouse, France and the §Department of Urology, Hopital Purpan, Place du Dr Baylac, 31052, Toulouse, France
Abstract
Vascular endothelial growth factor (VEGF) is a potent angiogenic factor which is synthesized and secreted by many differentiated cells in response to various stimuli including hypoxia and growth factor exposure. Alternative splicing of vascular endothelial growth factor mRNA results in three distinct molecular forms: V189 and V165 or V121 which lack the exons 6 or 6 and 7, respectively. To clarify the functions of the 24-amino acid insertion, the biological activity of V165 was compared with that exerted by purified recombinant V189 and a synthetic peptide designed on the sequence encoded by exon 6 (Ex6P). V189 and Ex6P, but not V165, induced cell proliferation on corneal endothelial cells cultured in vitro. These effects were due to the release of fibroblast growth factor 2 (FGF2) stored in the extracellular matrix but not to direct interactions with FGF receptors since V189 was inefficient on heparan sulfate-deficient cells expressing constitutively FGF-R1. Moreover corneas incubated ex vivo with Ex6P solubilized 10-fold more FGF2 than a isocationic peptide containing a scrambled sequence. Ex6P elicited an angiogenic response in a corneal pocket assay which was totally inhibited by addition of anti-FGF2 IgG. Moreover the angiogenic response to V189, but not to V165, was inhibited by FGF2 immunoneutralization. These findings demonstrate that the presence of the exon 6-encoded sequence confers VEGF with the ability to exert its biological effects through FGF2 signaling pathways.
Footnotes
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↵* This work was supported in part by grants from the Association de la Recherche pour le Cancer, Retina-France, and the Fondation de France.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵¶ Supported by the Fédération de la Recherche Médicale.
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↵‖ Present address: Dept. of Urology, Hopital Joseph Ducuing, 15 rue Varsovie, 31076, Toulouse, France.
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↵** To whom correspondence should be addressed. Tel.: 33-5-61-33-58-26; Fax: 33-5-61-33-58-86; E-mail: plouet{at}ibcg.biotoul.fr.
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↵1 The abbreviations used are: FGF, fibroblast growth factor; Ex6P, synthetic peptide RGKGKGQKRKRKKSRY; SP, synthetic peptide RKGKRQKGRKGKSKYR; V165, vascular endothelial growth factor 165; V189, vascular endothelial growth factor 189; uPA-V189, urokinase-cleaved V189; Pl-V189, plasmin-cleaved V189; PlGF, placenta growth factor 152; FBAE, bovine fetal aortic endothelial cells; BCE, bovine corneal endothelial cells; pgsA-745, heparan sulfate-deficient CHO cells; BHK, baby hamster kidney cells; PBS, phosphate-buffered saline; PDGF, platelet-derived growth factor; EGF, epidermal growth factor.
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- Received May 22, 1997.
- Revision received July 8, 1997.
