Airway inflammation is a hallmark of several pulmonary diseases and may be regulated by airway epithelial biochemical signals. One major mechanism that epithelial cells use to mediate leukocyte trafficking is regulation of the intercellular adhesion molecule-1(ICAM-1). This proposal is based on three observations regarding ICAM-1 expression on airway epithelial cells: 1) the level of ICAM-1 is regulated by an interferon-gamma (IFN-gamma)-induced signal transduction pathway which results in binding of a transcription factor, Stat1, to the inverted-repeat sequence of the interferon-gamma-response element (IRE) in the ICAM-1 promoter; 2) Sp1 is a constitutively produced transcription factor which binds to a GC-sequence in the interferon-gamma-response element of the ICAM-1 promoter and is required for Stat1 transcriptional activity; and 3) adenovirus type 5 (Ad5) infection inhibits interferon-gamma induced ICAM-1 expression. Based on these observation, the major hypothesis of this proposal is that modification of Stat1 function may allow for downregulation of overexuberant ICAM-1 expression but allow for physiologic ICAM-1 expression in airway epithelium. In this proposal, the candidate seeks to further define Stat1-DNA, Sp1-DNA and Stat1-Sp1 interactions and then modify IFN-gamma driven, Stat1-dependent regulation of ICAM-1 expression in airway epithelial cells.
The specific aims are the following: 1) To examine the effect of direct modification of Stat1 function on ICAM-1 expression. Using human tracheobronchial epithelial cells (hTBEC), DNA decoy and dominant negative strategies will be used to modify Stat1-dependent gene activation and resultant ICAM-1 expression and function. 2) To define the structure and function of Stat1/Sp1 interaction in ICAM-1 gene activation. Structure-function studies of Stat1 and Sp1 will be accomplished using assays of DNA/protein and protein/protein interaction. 3) To elucidate the biochemical basis for Ad 5 inhibition of IFN-gamma stimulated ICAM-1 expression. The selectivity and biochemical basis for Ad5 inhibition of IFN-dependent ICAM-1 expression will be investigated by examining components of the IFN-driven pathway leading to Stat1-dependent ICAM-1 expression.
