Abstract
Excess of nitric oxide (NO) induces apoptosis in some cell types, including macrophages. Heat shock protein of 70 kDa (hsp 70) has been reported to protect cells from various stresses, including apoptosis-inducing stimuli. Several cytosolic DnaJ homologs, partner chaperones of hsp 70 family members, have been identified in mammals. They include dj 1 (hsp 40/hdj-1) and dj 2 (HSDJ/hdj-2) . A question arose whether these chaperones are required to prevent NO-mediated apoptosis.
Apoptosis occured, when mouse macrophage-like RAW 264.7 cells were treated with an NO donor SNAP. This apoptosis could be prevented by pretreatment of the cells with heat or a low dose of SNAP. With these pretreatment, hsc 70 remained unchanged, whereas hsp 70 and dj 1 showed marked induction and dj 2 moderate induction. In transfection experiments, hsp 70, dj 1 or dj 2 alone was ineffective in preventing NO-mediated apoptosis. In contrast, both dj 1 and dj 2, in combination with hsp 70, prevented the cells from apoptosis. We also found that hsp 70-DnaJ chaperone pairs exert anti-apoptosic effects upstream of caspase 3 activation and also upstream of cytochrome c release from mitochondria.
