Mycobacterium tuberculosis heat shock protein 10 increases both proliferation and death in mouse P19 teratocarcinoma cells

: Exogenously added Mycobacterium tuberculosis Hsp10, either synthetic or recombinant, but not other related heat shock proteins (GroES from Escherichia coli or bovine Ubiquitin), increases apoptosis in serum-deprived P19 mouse teratocarcinoma cells. The effect is dose-dependent, with 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 inhibited by a polyclonal antibody raised against the synthetic protein. On the other hand, when the same cells are exponentially growing, M. tuberculosis Hsp10 increases cell proliferation with a bell-shaped dose-response curve and a moderate decrease in potency (peak-activity at 10(-8)-10(-7) M, with a 43.7 +/- 8.1% increase, mean +/- SD, n = 3). Therefore, it appears that this bacterial protein can exert two opposite effects, behaving either as a death- or as a growth-promoting factor, depending on the conditions of the target.