Tissue plasminogen activator binding to mouse cerebellar granule neurons

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Cerebellar cells secrete plasminogen activators (PAs), primarily tissue plasminogen activator (tPA) and urokinase plasminogen activator (uPA).
• Previous studies localized PA activity to cerebellar granule neurons and suggested secreted PA may bind to the neuron surface.

Purpose of the Study:

• To investigate the binding and functional activity of tissue plasminogen activator (tPA) on cerebellar granule neurons.
• To determine if granule neurons possess specific binding sites for tPA.

Main Methods:

• Cultures of neonatal mouse cerebellar cells were used.
• Fibrin overlay assays were employed to detect plasminogen activator activity.
• pH shock was used to displace cell-associated tPA.
• Exogenous mouse tPA, mouse uPA, and human PAs were incubated with cultures to assess binding and activity.

Main Results:

• Granule neurons secrete active tPA, which can be displaced by pH shock.
• Active mouse tPA specifically binds to granule neurons, retaining functional activity.
• Mouse uPA, human uPA, and human tPA did not show associated fibrinolytic activity on cerebellar cultures.
• Mouse tPA did not bind to cerebellar glial cell cultures.

Conclusions:

• Cerebellar granule neurons possess specific surface binding sites for tPA.
• Bound tPA on granule neurons retains its enzymatic activity.
• This interaction suggests a potential role for tPA in cerebellar granule neuron functions, such as cell migration.