Constitutive and PMA-induced interleukin-1 production by the human astrocytoma cell line T24.
Astrocytes and glial cells of different species produce interleukin-1 (IL-1) in vitro. In all cases, however, the evidence relied on the detection of IL-1 activity in biological assays. In this report we describe a human astrocytoma cell line (T24) which produces IL-1 constitutively and upon induction with phorbol myristate acetate in vitro. The IL-1 activity was detected in the culture supernatant by a modified assay measuring IL-1-dependent induction of IL-2 production by EL-4 cells. The active molecule had a molecular weight of 17 kDa on gel filtration and an isoelectric point of 5.2. The activity was not neutralized by a goat antibody reacting against pI 7 IL-1. In contrast, rabbit antibody reacting against pI 5 and pI 7 IL-1 neutralized all the IL-1 activity. Cell-associated IL-1 activity was detected in the supernatant of freeze-thawed cell lysates. Serological evidence as well as isoelectric point determination further supported that the predominant form of IL-1 synthesized was of the pI 5 type, and immunoprecipitation of 35S-labeled cell lysate with monospecific polyclonal antibody to IL-1 alpha or IL-1 beta detected only IL-1 alpha precursor. However, Northern blot analysis of astrocytoma cells indicated that mRNA encoding for both IL-1 species were present. These results, therefore, provide unequivocal evidence that human astrocytoma cells synthesize both forms of IL-1 message and yet only activity corresponding to the pI 5 form is detectable inside and outside these cells, suggesting that the inactive pI 7 IL-1 precursor, if made, is not processed to the mature active 17-kDa form.
Lee
J C
JC
Department of Immunology, Smith Kline & French Laboratories, Philadelphia, Pennsylvania 19101.
Simon
P L
PL
Young
P R
PR
D000595:Amino Acid Sequence; D001253:Astrocytes / Q000378:metabolism*; D001254:Astrocytoma / Q000503:physiopathology*; D001483:Base Sequence; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007375:Interleukin-1 / Q000096:biosynthesis*; D007526:Isoelectric Point; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D011233:Precipitin Tests; D012333:RNA, Messenger / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D007375:Interleukin-1; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D013755:Tetradecanoylphorbol Acetate