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.