title: Binding of madindoline A to the extracellular domain of gp130.
abstract: Elevated levels of IL-6 and IL-11 are associated with multiple myeloma, rheumatoid arthritis, hypercalcemia, cancer cachexia, and Castleman's disease. Madindoline A (MadA), isolated from Streptomyces nitrosporeus K93-0711, specifically inhibits the growth of IL-6- and IL-11-dependent cell lines, most likely by interfering with the homodimerization of gp130. This raises the possibility that MadA can be used as a model compound for the development of novel chemotherapeutic agents. In this report, we demonstrate that the binding of MadA to gp130 is specific and noncovalent, and displays a relatively low affinity. Furthermore, we show that the tricyclic 3a-hydroxytetrahydrofuro[2,3-b]indole (HFI) moiety of MadA alone is not sufficient for binding. Matrix-bound MadA precipitates a protein composed of the extracellular domain of gp130 fused to the Fc region of the immunoglobulin heavy chain. Binding is inhibited in a dose-dependent manner by preincubation with free MadA. The K(D) for binding of MadA to gp130 is 288 microM, as determined by surface plasmon resonance (SPR)-based biosensor analysis. The HFI portion of MadA does not bind to gp130 in either affinity precipitation or SPR analyses. Finally, MadA, but not the HFI portion, inhibits IL-6-dependent Stat3 tyrosine phosphorylation in HepG2 cells.
authors.affiliation: Department of Pathology, University of California, Irvine, California 92697, USA.
authors.forename: Abu Z M
authors.initials: AZ
authors.lastname: Saleh
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Greenman
authors.forename: Susan
authors.initials: S
authors.lastname: Billings
authors.forename: David L
authors.initials: DL
authors.lastname: Van Vranken
authors.forename: John J
authors.initials: JJ
authors.lastname: Krolewski
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D001665:Binding Sites; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000378:metabolism*; D045744:Cell Line, Tumor; D058966:Contactins; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000378:metabolism*; D019006:Neural Cell Adhesion Molecules / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D050796:STAT3 Transcription Factor; D020349:Surface Plasmon Resonance; D015534:Trans-Activators / Q000378:metabolism; D000093242:Interleukin-6 Inhibitors
chemical_list: D001426:Bacterial Proteins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D058966:Contactins; D004268:DNA-Binding Proteins; D007211:Indoles; D019006:Neural Cell Adhesion Molecules; D050796:STAT3 Transcription Factor; D015534:Trans-Activators; D000093242:Interleukin-6 Inhibitors; C494086:STAT3 protein, human; C103158:madindoline A