Human N-terminal analogs of interleukin 1 beta demonstrate altered binding and function in hematopoiesis.
This study describes the structure-function relationship of interleukin 1 beta (IL-1 beta) using two amino-terminal muteins of human IL-1 beta. One mutein, clone 18, which substitutes a threonine and methionine for the alanine and proline at positions 1 and 2 of the N-terminus of fully processed and active IL-1 beta, demonstrated similar activity to that of native IL-1 beta in inducing granulocyte-macrophage colony-stimulating activity (GM-CSA) from cultured fibroblasts. Clone 18 also demonstrated similar binding to IL-1 beta receptors on fibroblasts when using a competitive binding assay. The second mutein was GLU-4, which in addition to substituting alanine and proline by threonine and methionine also substituted glutamine for arginine at position 4 of the processed IL-1 beta molecule. GLU-4 required a 3-log increase in concentration to obtain the same GM-CSA release from fibroblasts and to produce the same amount of competitive binding inhibition as clone 18 and native IL-1 beta. In addition, preincubation of bone marrow cells with clone 18 and native IL-1 beta demonstrated a greater ability to protect early hematopoietic progenitors from the lethal effects of 4-hydroperoxycyclophosphamide when compared to similar concentrations of GLU-4. A greater number of large granulocyte-macrophage, erythroid, and mixed colonies as well as blast cell colonies were observed when bone marrow cells were preincubated for 20 h with clone 18 or native IL-1 beta as compared to preincubation with GLU-4 or medium alone. Therefore, arginine at position 4 of the processed IL-1 beta molecule was shown to be a key residue in the function of IL-1 beta as a hematopoietic regulator. These results also suggest that minor changes in the N-terminal sequence of IL-1 beta result in decreased interaction with its receptor and a subsequent reduction in biological activity.
Zucali
J R
JR
Department of Medicine, University of Florida, Gainesville 32610.
Moreb
J
J
Newton
R C
RC
Huaog
J J
JJ
D001667:Binding, Competitive; D001854:Bone Marrow Cells; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D003520:Cyclophosphamide / Q000031:analogs & derivatives / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism; D006098:Granulocytes / Q000166:cytology; D006410:Hematopoiesis / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects; D006801:Humans; D007375:Interleukin-1 / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D008264:Macrophages / Q000166:cytology; D016297:Mutagenesis, Site-Directed; D011869:Radioligand Assay; D011971:Receptors, Immunologic / Q000378:metabolism; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins / Q000502:physiology; D013329:Structure-Activity Relationship
D007375:Interleukin-1; D011971:Receptors, Immunologic; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D003520:Cyclophosphamide; C011272:perfosfamide