Plasminogen activator is enriched in the synaptosomal plasma membranes

Area of Science:

• Neuroscience
• Biochemistry

Background:

• Plasminogen activator is a serine protease.
• Its localization within the brain is not fully understood.

Purpose of the Study:

• To determine the intracellular localization of plasminogen activator in bovine brain cortex.
• To investigate its association with specific neuronal compartments.

Main Methods:

• Differential fractionation of bovine brain cortex homogenates.
• Enzyme activity assays.
• Subcellular marker analysis (cytosol, mitochondria, plasma membrane, synaptic membrane).
• Synaptosome and synaptic vesicle purification.

Main Results:

• Plasminogen activator distribution differed from cytosol and mitochondrial markers.
• Enzyme activity was enriched in fractions containing synaptic membrane markers and intact synaptosomes.
• The enzyme was primarily associated with the synaptosomal membrane, solubilized by salt or detergent.
• Two species (80,000 and 55,000 Da) of plasminogen activator were identified in synaptosomes.
• Purified synaptic vesicles showed low levels of the enzyme.

Conclusions:

• Plasminogen activator is predominantly localized to the synaptosomal membrane in bovine brain.
• The enzyme's presence in nerve terminals suggests a potential role in neuronal function.