Multiple glycosylated forms of T cell-derived interleukin 3 (IL-3). Heterogeneity of IL-3 from physiological and nonphysiological sources |
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Authors: | H J Ziltener B Fazekas de St Groth K B Leslie J W Schrader |
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Institution: | Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Victoria, Australia. |
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Abstract: | Interleukin 3 (IL-3) derived from mouse T cells was biosynthetically labeled with either 35S]methionine or 3H]mannose, affinity-purified using various anti-IL-3 antibodies, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Autoradiography revealed the same three major bands with Mr values of 21,500-22,500, 27,000-31,000, and 32,000-36,000, irrespective of whether the anti-IL-3 antibody had been directed to the N or C termini of the IL-3 polypeptide. Bioassay of eluates from the gels confirmed that all three bands exhibited IL-3 bioactivity. IL-3 produced from two nonphysiological sources, the myelomonocytic leukemia WEHI-3B or Cos 7 cells that had been transfected with an IL-3 cDNA clone, had in each case a different pattern of microheterogeneity. Treatment with either tunicamycin or N-glycanase resulted in IL-3 running as one band with Mr 16,000, corresponding to its 140-amino acid polypeptide chain. No evidence for proteolytic processing was detected. These results show that the Mr heterogeneity of IL-3 was highly dependent on the cellular source and is due to N-linked glycosylation. |
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