Involvement of Caspase-1 and Caspase-3 in the Production and Processing of Mature Human Interleukin 18 in Monocytic THP.1 Cells

Recently, human interleukin 18 (hIL-18) cDNA was cloned, and the recombinant protein with a tentatively assigned NH2-terminal amino acid sequence was generated. However, natural hIL-18 has not yet been isolated, and its cellular processing is therefore still unclear. To clarify this, we purified nat...

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Veröffentlicht in:The Journal of biological chemistry 1997-10, Vol.272 (42), p.26595-26603
Hauptverfasser: Akita, Kenji, Ohtsuki, Takashi, Nukada, Yoshiyuki, Tanimoto, Tadao, Namba, Motoshi, Okura, Takanori, Takakura-Yamamoto, Rohko, Torigoe, Kakuji, Gu, Yong, Su, Michael S.-S., Fujii, Mitsukiyo, Satoh-Itoh, Michiyo, Yamamoto, Kouzo, Kohno, Keizo, Ikeda, Masao, Kurimoto, Masashi
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Sprache:eng
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Zusammenfassung:Recently, human interleukin 18 (hIL-18) cDNA was cloned, and the recombinant protein with a tentatively assigned NH2-terminal amino acid sequence was generated. However, natural hIL-18 has not yet been isolated, and its cellular processing is therefore still unclear. To clarify this, we purified natural hIL-18 from the cytosolic extract of monocytic THP.1 cells. Natural hIL-18 exhibited a molecular mass of 18.2 kDa, and the NH2-terminal amino acid was Tyr37. Biological activities of the purified protein were identical to those of recombinant hIL-18 with respect to the enhancement of natural killer cell cytotoxicity and interferon-γ production by human peripheral blood mononuclear cells. We also found two precursor hIL-18 (prohIL-18)-processing activities in the cytosol of THP.1 cells. These activities were blocked separately by the caspase inhibitors Ac-YVAD-CHO and Ac-DEVD-CHO. Further analyses of the partially purified enzymes revealed that one is caspase-1, which cleaves prohIL-18 at the Asp36-Tyr37 site to generate the mature hIL-18, and the other is caspase-3, which cleaves both precursor and mature hIL-18 at Asp71-Ser72 and Asp76-Asn77 to generate biologically inactive products. These results suggest that the production and processing of natural hIL-18 are regulated by two processing enzymes, caspase-1 and caspase-3, in THP.1 cells.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.272.42.26595