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Cell Growth & Differentiation Vol. 11, 593-605, November 2000
© 2000 American Association for Cancer Research


Articles

NH2-Terminal Cleavage of Xenopus Fibroblast Growth Factor 3 Is Necessary for Optimal Biological Activity and Receptor Binding

Marianne Antoine, Markus Daum, Roman Köhl, Volker Blecken, M. James Close, Gordon Peters and Paul Kiefer1

Ruhr-Universität Bochum, Med. Fakultät, Abteilung für Virologie, D-44780 Bochum, Geb. MA 6/130, Germany [M. A., M. D., R. K., V. B., P. K.], and Imperial Cancer Research Fund Laboratories, London WC2A 3PX, United Kingdom [M. J. C., G. P.]

Abstract

Fibroblast growth factor 3 (FGF3) was originally identified as the mouse proto-oncogene Int-2, which is activated by proviral insertion in tumors induced by mouse mammary tumor virus. To facilitate the biological characterization of the ligand, we have analyzed its homologue in Xenopus laevis, XFGF3. Here we confirm that the X. laevis genome contains two distinct FGF3 alleles, neither of which is capable of encoding the NH2-terminally extended forms specified by the mouse and human FGF3 genes. Unlike the mammalian proteins, XFGF3 is efficiently secreted as a Mr 31,000 glycoprotein, gp31, which undergoes proteolytic cleavage to produce an NH2-terminally truncated product, gp27. Processing removes a segment of 18 amino acids immediately distal to the signal peptide that is not present in the mammalian homologues. By inserting an epitope-tag adjacent to the cleavage site, we show that a substantial amount of the gp27 is generated intracellularly, although processing can also occur in the extracellular matrix. Two residues are also removed from the COOH terminus. To compare the biological properties of the different forms, cDNAs were constructed that selectively give rise to the larger, gp31, or smaller, gp27, forms of XFGF3. As judged by their ability to cause morphological transformation of NIH3T3 cells, their mitogenicity on specific cell types, and their affinity for the IIIb and IIIc isoforms of Xenopus FGF receptors, gp27 has a much higher biological activity than gp31. Sequence comparison revealed an intriguing similar cleavage motif immediately downstream of the signal peptide cleavage site in the NH2-terminus of mouse and human FGF3. Analysis of secreted mutant mouse FGF3 confirmed an additional NH2-terminal processing at the corresponding sequence motif. NH2-terminal trimming of Xenopus and mammalian FGF3s may therefore be a prerequisite of optimal biological activity.







HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Cancer Research Clinical Cancer Research
Cancer Epidemiology Biomarkers & Prevention Molecular Cancer Therapeutics
Molecular Cancer Research Cell Growth & Differentiation
Copyright © 2000 by the American Association of Cancer Research.