Cleavage of K-FGF produces a truncated molecule with increased biological activity and receptor binding affinity

P. Bellosta, D. Talarico, D. Rogers, C. Basilico

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Abstract

The K-FGF/HST (FGF-4) growth factor is a member of the FGF family which is efficiently secreted and contains a single N-linked glycosylation signal. To study the role of glycosylation in the secretion of K-FGF, we mutated the human K-fgf cDNA to eliminate the glycosylation signal and the mutated cDNA was cloned into a mammalian expression vector. Studies of immunoprecipitation from the conditioned medium of cells expressing this plasmid revealed that the lack of glycosylation did not impair secretion, however the unglycosylated protein was immediately cleaved into two NH 2-terminally truncated peptides of 13 and 15 kD, which appeared to be more biologically active than the wild-type protein. These two proteins also showed higher heparin binding affinity than that of wt K-FGF. We have expressed in bacteria the larger of these two proteins (K140), in which the NH 2-terminal 36 amino acids present in the mature form of K-FGF have been deleted. Mitogenicity assays on several cell lines showed that purified recombinant K140 had approximately five times higher biological activity than wild-type recombinant K-FGF. Studies of receptor binding showed that K140 had higher affinity than wt K-FGF for two of the four members of FGF receptor's family, specifically for FGFR-1 (flg) and FGFR-2 (bek). K140 also had increased heparin binding ability, but this property does not appear to be responsible for the increased affinity for FGF receptors. Thus removal of the NH 2- terminal 36 amino acids from the mature K-FGF produces growth factor molecules with an altered conformation, resulting in higher heparin affinity, and more efficient binding to FGF receptors. Although it is not clear whether cleavage of K-FGF to generate K140 occurs in vivo, this could represent a novel mechanism of modulation of growth factor activity.

Original languageEnglish
Pages (from-to)705-713
Number of pages9
JournalJournal of Cell Biology
Volume121
Issue number3
Publication statusPublished - 1993

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Glycosylation
Fibroblast Growth Factor Receptors
Heparin
Intercellular Signaling Peptides and Proteins
Proteins
Complementary DNA
Amino Acids
Aptitude
Conditioned Culture Medium
Immunoprecipitation
Plasmids
Bacteria
Cell Line
Peptides

ASJC Scopus subject areas

  • Cell Biology

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Cleavage of K-FGF produces a truncated molecule with increased biological activity and receptor binding affinity. / Bellosta, P.; Talarico, D.; Rogers, D.; Basilico, C.

In: Journal of Cell Biology, Vol. 121, No. 3, 1993, p. 705-713.

Research output: Contribution to journalArticle

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