Homodimeric murine interleukin-3 agonists indicate that ligand dimerization is important for high-affinity receptor complex formation.
Homodimeric murine interleukin 3 (mIL-3) agonists were generated by intermolecular cystine-bonding. Steady-state binding assays and association kinetics performed at 4 degrees C using these agonists revealed specific binding to both the high- and low-affinity receptor. DSS-mediated crosslinking studies performed at 4 degrees C with agonist concentrations compatible with high-affinity receptor complex formation allowed to detect protein complexes of the alpha chain, the beta chain(s) and the high-affinity receptor complex migrating with apparent molecular weights of 90 kDa, 140 kDa, and above 180 kDa, respectively. In contrast, monomeric mIL-3 was crosslinked to the alpha chain receptor only unless high concentrations were used. Binding studies performed at 4 degrees C revealed a positive cooperative interaction of monomeric mIL-3 with the low-affinity receptor. Proliferation studies and association kinetics performed at 37 degrees C showed that under physiological conditions these agonists were at least 2- to 3-fold more potent than monomeric mIL-3. We therefore propose that dimerization of mIL-3 may be involved in high-affinity receptor complex formation.
Müther
H
H
Heinrich-Pette-Institut für Experimentelle Virologie und Immunologie, Universität Hamburg, Germany.
Kühlcke
K
K
Gessner
A
A
Abdallah
S
S
Lother
H
H
D000818:Animals; D001681:Biological Assay; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002461:Cell Line, Transformed; D003553:Cystine; D004591:Electrophoresis, Polyacrylamide Gel; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D007377:Interleukin-3 / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D015848:Interleukin-5 / Q000494:pharmacology; D007700:Kinetics; D008024:Ligands; D046911:Macromolecular Substances; D051379:Mice; D017433:Protein Structure, Secondary; D016185:Receptors, Interleukin-3 / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism
D007377:Interleukin-3; D015848:Interleukin-5; D008024:Ligands; D046911:Macromolecular Substances; D016185:Receptors, Interleukin-3; D011994:Recombinant Proteins; D003553:Cystine; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D013936:Thymidine