MAJOR STRESS PROTEIN HSP70 INTERACTS WITH NF-KB REGULATORY COMPLEX INHUMAN T-LYMPHOMA CELLS

Polypeptides belonging to the Hsp70 major stress protein family and to the NF-kB/Rel multi-functional regulatory complex are known to be inv olved in cellular defense mechanisms. It was suggested that both syste ms may interact in cells that respond to injuring stimuli. To check th is, Molt4 human lymphoma cells were heated at 43 degrees C for 15 min and, after a 6 h post-shock recovery period, the cells were activated with phorbol ester or bacterial lipopolysaccharide. It was found that mild heat shock caused a substantial increase of the intracellular Hsp 70 content with the concomitant suppression of NF-kB complexes, though the latter was properly activated in non-stressed cells. After a 24 h period of being inactive the complex fully recovered its activity and p65 and c-Rel subunits migrated to the nucleus. This new active perio d lasted even longer than that in non-heated control cells. As this su ggested the existence of a Hsp70-related mechanism of NF-kB/Rel comple x retention in cytoplasm, we carried out immunoprecipitation with the use of anti-Hsp70 and anti-Rel antibodies. All three Rel family member s p65, c-Rel, p50, but not their precursors and lkB alpha inhibitory p rotein were shown to co-precipitate with the stress protein and anti-H sp70 antibodies from both heated and non-heated cells. We conclude tha t the Hsp70 stress protein may confer a new mechanism of NF-kB regulat ion in cells affected by elevated temperature or other factors related to the cellular response to stress.