Hematopoietic differentiation activity of a recombinant human interleukin-6 (IL-6) isoform resulting from alternatively spliced deletion of the second exon.
We have previously identified and cloned an alternatively spliced form of human interleukin-6 mRNA lacking exon II, which encodes amino acid residues known to be important in gp130-mediated signal transduction pathways. We expressed and purified the recombinant protein (rIL6-alt) resulting from this alternatively spliced mRNA and now report the initial characterization of its biologic activities with comparison to full length IL6 (rIL6-full). rIL6-alt was found to have 10(4) to 10(5) fold less activity in proliferation assays with 7TD1 murine plasmacytoma cells and did not competitively inhibit the stimulatory activity of rIL6-full. In addition, like rIL6-full, rIL6-alt had antiproliferative activity toward M1 murine myeloblast cells and was 10-200-fold less active than rIL6-full. In contrast, in assays with human HL60 promyelocytic leukemia cells, rIL6-alt had greater antiproliferative activity than rIL6-full and more strongly upregulated phagocytosis as well as surface expression of the differentiation antigen CD11b. rIL6-full and rIL6-alt upregulated the level of lysozyme mRNA in HL60 cells approximately equally. These findings suggest that IL6-alt, which lacks amino acid residues encoded by the second exon of the gene, is not a natural inhibitor of IL6-full but may be relatively tissue specific and may play a role in modulation of hematopoietic cell growth and differentiation.
Kestler
D P
DP
Department of Medicine (Division of Hematology/Oncology), University of Tennessee Medical Center/Graduate School of Medicine, Knoxville, Tennessee, USA. dkestler@utk.edu
Goldstein
K M
KM
Agarwal
S
S
Fuhr
J E
JE
Andrews
R
R
Hall
R E
RE
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D003001:Cloning, Molecular; D005091:Exons; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018922:HL-60 Cells; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects; D006801:Humans; D015850:Interleukin-6 / Q000737:chemistry / Q000235:genetics* / Q000494:pharmacology*; D051379:Mice; D008969:Molecular Sequence Data; D009113:Muramidase / Q000235:genetics; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000494:pharmacology; D017384:Sequence Deletion; D015398:Signal Transduction
D015850:Interleukin-6; D020033:Protein Isoforms; D012333:RNA, Messenger; D011994:Recombinant Proteins; D009113:Muramidase