alpha-l-antichymotrypsin (ACT) is a serine proteinase inhibitor (serpin) that specifically co-localizes with beta-amyloid deposits in the brains of Alzheimer's patients. ACT also enhances the formation of beta-amyloid deposits in a double transgenic mouse model of Alzheimer's disease. Astrocytes are the major source of ACT found in the brain and expression of this serpin is enhanced during brain inflammatory processes. The goals of this research proposal have been designed to elucidate mechanisms of tissue-specific expression of ACT in human brain astrocytes and its up-regulation by IL-1 and tumor necrosis factor (TNF) in these cells. The gene encoding ACT is located in a distal serpin subcluster on chromosome 14q32.1. All genes located in this subcluster are expressed in hepatocytes but only the ACT gene is transcribed in astrocytes. In addition, hepatocyte-specific transcription factors are not expressed in astrocytes. Based on our preliminary studies we hypothesized that """"""""astrocyte specific"""""""" chromatin structure of this distal subcluster determines the expression pattern of serpin genes in the brain. However, tissue-specific transcription factors that determine this """"""""astrocyte specific"""""""" structure are not known and their identification is critical for a full understanding of the tissue-specific expression of the ACT gene. Therefore, we propose the following specific aims: 1) To compare the chromatin structure of the distal serpin subcluster in astrocytes to that in hepatocytes and tissue-specific microcell hybrids. 2) To identify the specific regulatory elements and transcription factors that are responsible for astrocyte-specific expression of the ACT gene. 3) To identify the mechanism of tissue-specific activation of the ACT gene by IL-1 and TNF.
