title: Macrophage stimulating protein (MSP) binds to its receptor via the MSP beta chain.
abstract: Macrophage stimulating protein (MSP) is a 78-kDa disulfide-linked heterodimer belonging to the plasminogen-related kringle protein family. MSP activates the RON receptor protein-tyrosine kinase, which results in cell migration, shape change, or proliferation. A structure-activity study of MSP was performed using pro-MSP, MSP, MSP alpha and beta chains, and a complex including the first two kringles and IgG Fc (MSP-NK2). Radioiodinated MSP and MSP beta chain both bound specifically to RON. The Kd of 1.4 nM for MSP beta chain is higher than the reported Kd range of 0.6-0.8 nM for MSP. Pro-MSP, MSP alpha chain, and MSP-NK2 did not bind. Only MSP stimulated RON autophosphorylation. Although the beta chain bound to RON and partially inhibited MSP-induced RON phosphorylation in kidney 293 cells, it did not induce RON phosphorylation. Pro-MSP, MSP alpha chain, or MSP-NK2 failed to activate RON, consistent with their inability to bind to the RON receptor. Functional studies showed that only MSP induced cell migration, and shape change in resident macrophages, and growth of murine keratinocytes. Our data indicate that the primary receptor binding domain is located in a region of the MSP beta chain, in contrast to structurally similar hepatocyte growth factor, in which the receptor binding site is in the alpha chain. However, full activation of RON requires binding of the complete MSP disulfide-linked alphabeta chain heterodimer.
authors.affiliation: Laboratory of Immunobiology, National Cancer Institute, Frederick Cancer Research and Development Center, Frederick, Maryland 21702, USA.
authors.forename: M H
authors.initials: MH
authors.lastname: Wang
authors.forename: F M
authors.initials: FM
authors.lastname: Julian
authors.forename: R
authors.initials: R
authors.lastname: Breathnach
authors.forename: P J
authors.initials: PJ
authors.lastname: Godowski
authors.forename: T
authors.initials: T
authors.lastname: Takehara
authors.forename: W
authors.initials: W
authors.lastname: Yoshikawa
authors.forename: M
authors.initials: M
authors.lastname: Hagiya
authors.forename: E J
authors.initials: EJ
authors.lastname: Leonard
mesh_terms: D016475:3T3 Cells; D000042:Absorption; D000818:Animals; D001667:Binding, Competitive; D002455:Cell Division; D002465:Cell Movement; D048429:Cell Size; D019281:Dimerization; D006133:Growth Substances / Q000235:genetics / Q000378:metabolism*; D017228:Hepatocyte Growth Factor; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008970:Molecular Weight; D010766:Phosphorylation; D011487:Protein Conformation; D011498:Protein Precursors / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D014443:Tyrosine / Q000378:metabolism
chemical_list: D006133:Growth Substances; D011498:Protein Precursors; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; C082332:macrophage stimulating protein; D014443:Tyrosine; D017228:Hepatocyte Growth Factor; C080835:RON protein; D020794:Receptor Protein-Tyrosine Kinases