Chimeric Molecules between Keratinocyte Growth Factor and Basic Fibroblast Growth Factor Define Domains That Confer Receptor Binding Specificities (*)
- From the Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel
- Department of Experimental Medicine and Biochemical Sciences, Via Orazio Raimondo, 00173 Roma, Italy
- § To whom correspondence should be addressed. Tel.: 972-4-294217; Fax: 972-4-225153.
Abstract
Basic fibroblast growth factor (FGF) and keratinocyte growth factor (KGF) are structurally related fibroblast growth factors,
yet they exhibit distinct receptor binding specificity. Basic FGF binds with high affinity to FGFR1, FGFR2, and FGFR4, whereas
KGF does not interact with these receptors and can only bind an isoform of FGFR2 known as the KGFR. Basic FGF binds KGFR but
with lower affinity than KGF. In order to identify domains that confer this specificity, four reciprocal chimeras were generated
between the two growth factors and were analyzed for receptor recognition and biological activity. The chimeras are designated
BK1 (bFGF
:KGF
), BK2 (bFGF
:KGF
), KB1 (KGF
:bFGF
), and KB2 (KGF
:bFGF
). The two BK chimera similarly interacted with FGFR1 and FGFR4 but differed from each other with respect to KGFR recognition.
BK1 displayed a slightly better affinity for KGFR than BK2 and induced a higher level of DNA synthesis in keratinocytes compared
with bFGF and BK2. A neutralizing monoclonal antibody directed against bFGF specifically neutralized the biological activity
of the BK chimeras. The reciprocal chimeras, KB1 and KB2, exhibited KGF-like receptor binding and activation properties. However,
KB2 displayed higher affinity for KGFR and was significantly more potent mitogen than KB1. Altogether, our results suggest
that the amino-terminal part of KGF and bFGF plays an important role in determining their receptor binding specificity. In
addition, the results point to the contribution of a segment from the middle part of KGF (residues 91-110) for recognition
and activation of the KGFR, as the two chimeras containing these residues (BK1 and KB2) displayed an enhanced interaction
with the KGFR.
Footnotes
-
↵* This work was supported by grants from the Tobacco Research Council and the Israeli Cancer Research Fund and partially supported by grants from the Israel National Academy of Science and the Gesellschaft Fuer Biotechnologische Forschung-GBF (to D. R.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 The abbreviations used are:
- bFGF
-
basic fibroblast growth factor
- KGF
-
keratinocyte growth factor
- FGF
-
fibroblast growth factor
- FGFR
-
fibroblast growth factor receptor
- aFGF
-
acidic fibroblast growth factor
- HS
-
heparan sulfate
- KGFR
-
keratinocyte growth factor receptor
- PAGE
-
polyacrylamide gel electrophoresis.
-
- Received July 26, 1995.
- Revision received September 27, 1995.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
