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Polypeptides belonging to the Hsp70 major stress protein family and to the NF-kB/Rel multi-functional regulatory complex are known to be involved in cellular defense mechanisms. It was suggested that both systems may interact in cells that respond to injuring stimuli. To check this, 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 Hsp70 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 period lasted even longer than that in non-heated control cells. As this suggested the existence of a Hsp70-related mechanism of NF-kB/Rel complex retention in cytoplasm, we carried out immunoprecipitation with the use of anti-Hsp70 and anti-Rel antibodies. All three Rel family members p65, c-Rel, p50, but not their precursors and IkB alpha inhibitory protein were shown to co-precipitate with the stress protein and anti-Hsp70 antibodies from both heated and non-heated cells. We conclude that the Hsp70 stress protein may confer a new mechanism of NF-kB regulation in cells affected by elevated temperature or other factors related to the cellular response to stress.

Localized adherence (LA) of enteropathogenic Escherichia coli (EPEC) to epithelial cells results in attaching and effacing of the surface of these cells.

The aim of this study was to test the hypothesis that salinity can affect indirectly the nitrate acquisition by a negative modulation triggered by glutamine accumulation. Cowpea plants were exposed to a mild NaCl concentration (50 mM) in order to restrict growth and N-demand. After 21 d, pretreated plants and control plants were supplied with 0, 5 and 10 mM of Ca(NO 3 ) 2 for 3 d in absence of NaCl. Salt pretreated plants showed a great limitation in acquisition of NO 3 ⎯, indicated by decline in the nitrate uptake rate, NO 3 ⎯ accumulation, nitrate reductase activity and protein content. The restriction of NO 3 ⎯ utilization was positively associated with increased glutamine synthetase activity and glutamine accumulation, especially in roots.

No abstract