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Endotoxin-stimulated monocytes release multiple forms of IL-1 beta, including a proIL-1 beta form whose detection is
M D Wewers1, A V Winnard, H A Dare
1Department of Pulmonary and Critical Care Medicine, Ohio State University, Columbus 43210, USA. wewers.2@osu.edu
Journal of Immunology (Baltimore, Md. : 1950)
|April 14, 1999
Summary
Interleukin-1 beta (IL-1 beta) is released from monocytes in multiple forms, including a 31-kDa proIL-1 beta that differs conformationally from its cytosolic counterpart. This finding sheds light on IL-1 beta secretion mechanisms.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- The precise mechanisms governing the processing and release of Interleukin-1 beta (IL-1 beta) remain incompletely understood.
- IL-1 beta exists in precursor (proIL-1 beta) and mature forms, with its secretion pathway being a key area of research.
Purpose of the Study:
- To investigate the various molecular forms of IL-1 beta released from stimulated monocytes.
- To characterize the properties of the released proIL-1 beta and compare it to intracellular proIL-1 beta.
Main Methods:
- Utilized immunoprecipitation with [35S]methionine labeling, Western blotting, and a newly developed ELISA specific for proIL-1 beta.
- Analyzed IL-1 beta forms released from endotoxin-stimulated human monocytes.
- Employed SDS-PAGE with densitometry, ICE processing assays, and nondenaturing gel electrophoresis.
Main Results:
- Demonstrated that monocytes release IL-1 beta not only as the mature 17-kDa form but also as 31-, 28-, and 3-kDa molecules.
- The 31-kDa released proIL-1 beta constituted 20-40% of total released IL-1 beta and exhibited altered properties compared to cytosolic proIL-1 beta.
- Released proIL-1 beta was not detectable by ELISA, suggesting a conformational change upon release, and did not complex with the type II IL-1 receptor.
Conclusions:
- IL-1 beta is exported from monocytes in multiple forms: 3-, 17-, 28-, and 31-kDa.
- The released 31-kDa proIL-1 beta undergoes a conformational change distinct from its intracellular state.
- These findings provide new insights into the complex secretion pathways of IL-1 beta.