Reduced expression of CD45 Protein-Tyrosine Phosphatase Pr

摘要

The modulation of cellular processes by small molecule inhibitors, gene inactivation or targeted knock-down approaches combined with phenotypic screens are powerful approaches to delineate complex cellular pathways and to identify key players involved in disease pathogenesis. Using chemical genetic screening, we tested a library of known phosphatase inhibitors and identified several compounds that protected Bacillus anthracis infected macrophages from cell death. The most potent compound was assayed against a panel of sixteen different phosphatases of which CD45 was found to be most sensitive to inhibition. Testing of a known CD45 inhibitor also protected B. anthracis infected macrophages from cell death. Subsequently, in vivo studies were conducted with both gene targeted knock down of CD45 and genetically engineered mice expressing reduced levels of CD45. Under both conditions, mice were protected following infection with the virulent Ames B. anthracis. In contrast, wild type mice, mice with disrupted CD45 phosphatase activity and CD45 knockout mice succumbed to these pathogens. Mechanism-based studies suggest that the protection provided by reduced CD45 levels resulted from dynamic host immunity via accelerated immune cell homeostasis that may diminish the impact of apoptosis during the infection. An important implication of this study is that compounds identified based on their ability to produce specific cellular phenotypes can be valuable research tools. Furthermore, if the therapeutic class of the compound is known, the typically arduous challenge of molecular target identification is significantly more efficient.