Serine proteases in rodent hippocampus

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Brain serine proteases play crucial roles in neural development, synaptic plasticity, and neurological disorders like Alzheimer's disease.
• A comprehensive understanding of the major serine proteases expressed in the brain is currently lacking.

Purpose of the Study:

• To systematically identify and characterize the spectrum of serine proteases expressed in the adult rat and mouse hippocampus.
• To report novel serine protease sequences and their expression patterns within the brain.

Main Methods:

• Utilized polymerase chain reaction (PCR) amplification and Northern blotting to analyze gene expression.
• Sequenced full-length cDNAs for newly identified brain serine proteases.

Main Results:

• Tissue-type plasminogen activator (t-PA) was identified as the most abundant serine protease in the hippocampus.
• RNK-Met-1, a lymphocyte protease, and two novel serine proteases, BSP1 and BSP2, were unexpectedly found to be highly expressed.
• BSP1 expression was notably restricted to the hippocampus, while BSP2 showed broader brain region distribution.
• Lower levels of elastase IV, proteinase 3, complement C2, chymotrypsin B, and Hageman factor were detected.
• Thrombin and urokinase-type plasminogen activator (u-PA) showed low-level expression upon specific PCR confirmation.
• Plasminogen, a key substrate for t-PA, was not detected at significant levels.

Conclusions:

• The hippocampus expresses a diverse array of serine proteases, with t-PA being predominant.
• The discovery of RNK-Met-1, BSP1, and BSP2 expands the known repertoire of brain-expressed proteases, highlighting potential new roles in neural function.
• The restricted hippocampal expression of BSP1 suggests a specialized function within this brain region.
• The absence of detectable plasminogen despite high t-PA levels raises questions about the regulation of the fibrinolytic system in the brain.