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Characterization of astrocyte plasminogen activator.
P K Toshniwal1, S L Firestone, G H Barlow
1Division of Neurology, Cook County Hospital, Chicago, IL 60612.
Journal of the Neurological Sciences
|September 1, 1987
Summary
Astrocytes secrete tissue plasminogen activator (t-PA), an enzyme that breaks down fibrin. This finding helps explain myelin injury and demyelination in neurological conditions.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- Astrocytes are known to produce plasminogen activator (PA).
- The specific type and function of PA produced by astrocytes require further characterization.
- Previous studies noted correlations between fibrin deposition, demyelination, and therapeutic interventions in experimental allergic encephalomyelitis.
Purpose of the Study:
- To identify the specific type of plasminogen activator (PA) secreted by astrocytes.
- To characterize the biochemical properties of astrocyte-secreted PA.
- To explore the potential role of astrocyte-derived PA in myelin injury and demyelination.
Main Methods:
- Astrocytes were cultured, and their conditioned medium (CM) was analyzed.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to separate proteins in CM.
- Plasminogen activator activity was localized using a fibrin-agar gel overlay assay.
- Affinity chromatography with a tissue plasminogen activator (t-PA) antibody was performed.
- The binding of CM PA to fibrin clots was assessed.
Main Results:
- PA activity in astrocyte CM comigrated with purified t-PA standards on SDS-PAGE.
- Astrocyte-derived PA specifically bound to a t-PA antibody, which also inhibited its fibrinolytic activity.
- CM PA demonstrated the ability to bind to fibrin.
- These results strongly indicate that the PA secreted by astrocytes is tissue plasminogen activator (t-PA).
Conclusions:
- The enzyme produced and secreted by astrocytes is identified as tissue plasminogen activator (t-PA).
- Astrocyte-derived t-PA may play a role in myelin injury.
- This finding offers a potential explanation for the observed link between fibrin deposition, demyelination, and the effects of ancrod and heparin in experimental allergic encephalomyelitis.