Brain-specific angiogenesis inhibitor 2 (BAI2) may be activated by proteolytic processing.

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Brain-specific angiogenesis inhibitor 2 (BAI2) is an adhesion G protein-coupled receptor (GPCR) predominantly expressed in the brain.
• The physiological ligands and precise functions of BAI2 remain largely unknown.
• Adhesion-GPCRs, including BAI2, possess a long N-terminal extracellular region (ECR) with a conserved GPCR proteolysis site (GPS) domain, crucial for their activity.

Purpose of the Study:

• To investigate the proteolytic processing and activation mechanism of BAI2.
• To elucidate the role of GPS domain cleavage in BAI2 function.
• To identify the downstream signaling pathways activated by BAI2.

Main Methods:

• Identification of cleaved BAI2 C-terminal fragments in mouse hippocampus.
• Site-directed mutagenesis of the BAI2 GPS domain to assess proteolysis.
• Co-immunoprecipitation to detect the association between ECR and 7TM fragments.
• Analysis of BAI2 processing by furin prohormone convertase.
• NFAT pathway activation assays.

Main Results:

• Several cleaved C-terminal fragments of BAI2 were identified in mouse brain tissue.
• Mutation within the GPS domain inhibited BAI2 proteolysis, confirming GPS-mediated cleavage.
• The extracellular region (ECR) and C-terminal seven-transmembrane (7TM) fragment remained associated post-GPS cleavage.
• Furin prohormone convertase was identified as an enzyme cleaving BAI2 at an alternative site within the ECR.
• The C-terminal fragment, generated by GPS cleavage, specifically activated the nuclear factor of activated T-cells (NFAT) pathway.

Conclusions:

• BAI2 is a functional GPCR whose activity is regulated by proteolytic processing.
• Cleavage at the GPS domain is a key step in BAI2 activation.
• Activated BAI2 signaling converges on the NFAT pathway.