Abstract

Abstract The major form of IL-1 beta-converting enzyme (ICE) identified in THP.1 monocytic cells and human monocytes is the 45-kDa precursor protein (p45), which is found in the cytoplasm. Cytoplasmic extracts of these cells show no pIL-1 beta cleavage activity, indicating that the p45 has no detectable catalytic activity. pIL-1 beta cleavage activity can only be observed after incubation in vitro when p45 breaks down to the active p20 form of the enzyme. LPS stimulation of human monocytes or THP.1 monocytic cells results in no change in the amount of p45 or its activity and no detectable appearance of p20 ICE. Immunoprecipitation of [35S]Met-labeled LPS-stimulated monocyte extracts revealed only p45 with no other co-precipitating protein. The inability to identify active ICE in stimulated monocytic cells was probably a reflection of the very low levels of active ICE present.

Keywords

THP1 cell lineImmunoprecipitationMonocyteCytoplasmEnzymeChemistryCleavage (geology)Enzyme assayIn vitroBiochemistryMolecular biologyStimulationIncubationCell cultureBiologyGeneImmunology

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Publication Info

Year
1994
Type
article
Volume
153
Issue
6
Pages
2592-2599
Citations
114
Access
Closed

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Julia M. Ayala, Ting-Ting Yamin, Linda A. Egger et al. (1994). IL-1 beta-converting enzyme is present in monocytic cells as an inactive 45-kDa precursor.. The Journal of Immunology , 153 (6) , 2592-2599. https://doi.org/10.4049/jimmunol.153.6.2592

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DOI
10.4049/jimmunol.153.6.2592