Synthesis of Apolipoprotein A-1 in Pig Brain Microvascular Endothelial Cells

In an approach toward the identification of hitherto unknown proteins involved in the function of the blood-brain barrier, we constructed a pig brain microvessel-derived cDNA library that is enriched in blood-brain barrier specific sequences by means of subtractive cloning. Sequence analysis of selected clones revealed that one of the cDNAs encoded porcine apolipoprotein (apo) A-1. The identity of apo A-1 mRNA was further confirmed by in vitro translation of RNA from brain microvascular endothelial cells and subsequent immunoprecipitation with an antibody against human apo A-1. We further investigated the expression of apo A-1 mRNA in several tissues and in endothelial cells of the pig. It is shown that cultured brain microvascular endothelial cells provide an in vitro model to study the expression and function of apo A-1 in the microvasculature of the brain.