IDENTIFICATION OF MACROPHAGE AND STRESS-INDUCED PROTEINS OF MYCOBACTERIUM-TUBERCULOSIS

Using phosphorimager technology to quantitate differences in protein e xpression, we have investigated the modulation of protein synthesis by Mycobacterium tuberculosis in response to intracellular residence in human macrophages and, for comparison, in response to various stress c onditions during extracellular growth. Proteins of M. tuberculosis gro wing intracellularly in human THP-1 cells and extracellularly in broth were labeled with [S-35]methionine; during intracellular growth, host cell protein synthesis was inhibited with cycloheximide. The metaboli cally labeled proteins were separated by two-dimensional gel electroph oresis and quantitatively analyzed. Intracellular residence in macroph ages induced a profound change in the overall phenotype of M. tubercul osis. The expression of at least 16 M. tuberculosis proteins was induc ed (at least a twofold increase compared with growth in broth) and 28 proteins repressed (at least a twofold decrease). Many of the phenotyp ic changes in protein expression induced during intracellular growth o ccurred during extracellular growth in response to stress conditions i ncluding heat-shock, low pH, and H2O2. However, the pattern of induced and repressed proteins was unique to each stress condition. Of the 16 macrophage-induced proteins, 6 were absent during extracellular growt h under both normal and stress conditions. Such proteins are potential virulence determinants and/or they may be important in the cell-media ted and protective immune response to M. tuberculosis infection.