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Selective deimination of vimentin in calcium ionophore-induced apoptosis of mouse peritoneal macrophages
1Department of Cell Chemistry, Tokyo Metropolitan Institute of Gerontology, Japan. asagahi@tmig.or.jp
Abstract:
We found citrulline-containing proteins in mouse peritoneal macrophages undergoing calcium ionophore-induced apoptosis. Such proteins were products of deimination of arginine residues catalyzed by endogenous peptidylarginine deiminase (EC 3.5.3.15) activated by calcium influx. Western blotting analyses of the extract from macrophages incubated with 1 microM ionomycin showed selective deimination of vimentin without detectable degradation. Double immunofluorescence staining of deiminated proteins and vimentin suggested localization of deiminated vimentin around the periphery of round-shaped nucleus, which was thought to be an early morphological sign of apoptosis. The biological implication of vimentin deimination in macrophage apoptosis is discussed.
Insights
Calcium influx triggers peptidylarginine deiminase activation in macrophages, leading to citrullinated proteins like vimentin during apoptosis. This deimination occurs without protein degradation and may signal early apoptotic changes.
Area of Science:
- Cell Biology
- Biochemistry
- Immunology
Background:
- Apoptosis is a crucial cellular process.
- Macrophage apoptosis plays a role in immune regulation.
- Protein modification can influence cellular functions.
Purpose of the Study:
- To investigate protein modifications during calcium ionophore-induced macrophage apoptosis.
- To identify specific proteins affected by deimination in this process.
- To explore the role of peptidylarginine deiminase in macrophage cell death.
Main Methods:
- Induction of apoptosis in mouse peritoneal macrophages using calcium ionophore (ionomycin).
- Western blotting to detect citrulline-containing proteins and vimentin.
- Double immunofluorescence staining to localize deiminated proteins and vimentin.
Main Results:
- Citrulline-containing proteins were identified in apoptotic macrophages.
- Selective deimination of vimentin was observed without degradation.
- Deiminated vimentin localized peripherally around the nucleus, an early sign of apoptosis.
Conclusions:
- Calcium influx activates peptidylarginine deiminase, leading to vimentin deimination in macrophages.
- Vimentin deimination is a novel modification occurring during apoptosis.
- This modification may serve as an early morphological indicator of macrophage apoptosis.