MYCOBACTERIUM-TUBERCULOSIS HEAT-SHOCK PROTEIN-10 INCREASES BOTH PROLIFERATION AND DEATH IN MOUSE P19 TERATOCARCINOMA CELLS

Exogenously added Mycobacterium tuberculosis Hsp10, either synthetic o r recombinant, but not other related heat shock proteins (GroES from E scherichia coli or bovine Ubiquitin), increases apoptosis in serum-dep rived P19 mouse teratocarcinoma cells. The effect is dose-dependent, w ith a bell-shaped curve and peak activity at 10(-9) M (maximal effect: 62.9 +/- 17.7% increase, mean +/- SD, n = 10) and is specifically inh ibited by a polyclonal antibody raised against the synthetic protein. On the other hand, when the same cells are exponentially growing, M. t uberculosis Hsp10 increases cell proliferation with a bell-shaped dose -response curve and a moderate decrease in potency (peak-activity at 1 0(-8)-10(-7) M, with a 43.7 +/- 8.1%, increase, mean +/- SD, n = 3). T herefore, it appears that this bacterial protein can exert two opposit e effects,behaving either as a death- or as a growth-promoting factor, depending on the conditions of the target.