Heparin binding and oligomerization of hepatocyte growth factor/scatter factor isoforms. Heparan sulfate glycosaminoglycan requirement for Met binding and signaling.
Hepatocyte growth factor/scatter factor (HGF/SF) is a heparin-binding polypeptide that stimulates cell proliferation, motility, and morphogenesis by activation of its receptor, the c-Met tyrosine kinase. HGF/SF consists of a series of structural units, including an amino-terminal segment with a hairpin loop, four kringle domains, and a serine protease-like region. In this study, we demonstrate that the amino-terminal (N) domain retains the heparin-binding properties of full-length HGF/SF. In contrast to a previous hypothesis, selected basic amino acid residues in the hairpin loop are not critical for heparin binding, although alanine substitution at a subset of these sites markedly reduced the biological activity of the HGF/SF isoform, HGF/NK1. Covalent cross-linking experiments performed with wild-type and heparan sulfate glycosaminoglycan (HSGAG)-deficient Chinese hamster ovary (CHO) cells revealed that Met-HGF/NK1 binding was strongly dependent on HSGAG. Addition of heparin to HSGAG-deficient CHO cells not only restored ligand binding, but also increased ligand-dependent Met tyrosine phosphorylation and c-fos expression. Moreover, our results showed that heparin stimulated ligand oligomerization through an interaction with the N domain. These findings establish the importance of the N domain for heparin-ligand and ligand-ligand interactions, and demonstrate a crucial role for HSGAG in receptor binding and signal transduction.
Sakata
H
H
Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA.
Stahl
S J
SJ
Taylor
W G
WG
Rosenberg
J M
JM
Sakaguchi
K
K
Wingfield
P T
PT
Rubin
J S
JS
D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D006224:Cricetinae; D006493:Heparin / Q000378:metabolism*; D006497:Heparan Sulfate / Q000378:metabolism*; D017228:Hepatocyte Growth Factor / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D011487:Protein Conformation; D019859:Proto-Oncogene Proteins c-met; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D013329:Structure-Activity Relationship
D006493:Heparin; D006497:Heparan Sulfate; D017228:Hepatocyte Growth Factor; D008715:Methionine; D019859:Proto-Oncogene Proteins c-met; D020794:Receptor Protein-Tyrosine Kinases