Identification of macrophage and stress-induced proteins of Mycobacterium tuberculosis

Using phosphorimager technology to quantitate differences in protein expression, we have investigated the modulation of protein synthesis by Mycobacterium tuberculosis in re-sponse to intracellular residence in human macrophages and, for comparison, in response to various stress conditions during extracellular growth. Proteins of M. tuberculosis growing intracellularly in human THP-1 cells and extracel-lularly in broth were labeled with [3S]methionine; during intracellular growth, host cell protein synthesis was inhib-ited with cycloheximide. The metabolically labeled proteins were separated by two-dimensional gel electrophoresis and quantitatively analyzed. Intracellular residence in macro-phages induced a profound change in the overall phenotype ofM. tuberculosis. The expression of at least 16 M. tuberculo-sis proteins was induced (at least a twofold increase com-pared with growth in broth) and 28 proteins repressed (at least a twofold decrease). Many of the phenotypic changes in protein expression induced during intracellular growth occurred during extracellular growth in response to stress conditions including heat-shock, low pH, and H202. How-ever, the pattern of induced and repressed proteins was unique to each stress condition. Of the 16 macrophage-in-duced proteins, 6 were absent during extracellular growth under both normal and stress conditions. Such proteins are potential virulence determinants and/or they may be im-portant in the cell-mediated and protective immune re-sponse to M. tuberculosis infection. (J. Clin. Invest. 1995