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Production and secretion of plasminogen in cultured rat brain microglia
K Nakajima1, N Tsuzaki, K Nagata
1Department of Neurochemistry, National Institute of Neuroscience, Tokyo, Japan.
Abstract:
The production and secretion of plasminogen in cultured rat brain microglia was investigated. Urokinase-dependent caseinolytic activity was detected by zymography in microglial conditioned medium with a molecular weight of about 90 kDa. The 90-kDa protein was also detected by Western blotting with anti-rat plasminogen antiserum in the non-reducing condition. Immunoprecipitation with plasminogen antiserum following [35S]methionine labelling revealed that the plasminogen detected in microglial conditioned medium is synthesized in microglia. The amount of plasminogen in the conditioned medium was increased by stimulation with lipopolysaccharide. These results show that cultured microglia produce plasminogen and secrete it into the culture medium.
Insights
Cultured rat brain microglia produce and secrete plasminogen, a key protein in the fibrinolytic system. Lipopolysaccharide stimulation increased plasminogen levels in microglial conditioned medium.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Microglia are the primary immune cells of the central nervous system.
- The fibrinolytic system, involving plasminogen, plays a role in various physiological and pathological processes within the brain.
Purpose of the Study:
- To investigate the production and secretion of plasminogen by cultured rat brain microglia.
- To determine if microglia synthesize plasminogen and how its secretion is affected by inflammatory stimuli.
Main Methods:
- Zymography was used to detect caseinolytic activity in microglial conditioned medium.
- Western blotting and immunoprecipitation with specific antisera were employed to identify and confirm plasminogen.
- [35S]methionine labeling was utilized to assess de novo synthesis of plasminogen by microglia.
Main Results:
- A urokinase-dependent caseinolytic activity of approximately 90 kDa was detected in microglial conditioned medium.
- This 90-kDa protein was identified as plasminogen using Western blotting and immunoprecipitation.
- Microglia were confirmed to synthesize plasminogen, as shown by [35S]methionine labeling.
- Lipopolysaccharide stimulation led to an increased amount of plasminogen in the conditioned medium.
Conclusions:
- Cultured rat brain microglia actively produce and secrete plasminogen.
- Microglial plasminogen production is enhanced by lipopolysaccharide, suggesting a role in neuroinflammation.