[Induction and accumulation of HSP70 leads to formation of its complexes with other cell proteins].
The expression of a major stress protein Hsp70 may be induced by a great number of cytotoxic agents and also by factors known to cause process of cell proliferation or apoptosis. After induction the synthesis of Hsp70 is reduced to its basic level within first 2-6 hours after inducer application, while the high content of the protein may persist up to several days. The aim of this study was to understand the reason of such a long storage of Hsp70 in U-937 cells induced with three distinct factors. The data of immunoblotting showed that the mild heat shock at 43 degrees C for 60 min, phorbol ester and tumor necrosis factor (the two latter known to induce differentiation and apoptosis, respectively) caused Hsp70 accumulation, the protein level being high within 48 hours and then slowly declined to the basal level. According to the results of chromatography on anti-Hsp70 antibody-Sepharose gel, approximately 50% of the protein was retarded by the gel, while the other part was not recognized by immunoglobulins. Among proteins bound to the Hsp70, three polypeptides were identified as actin, p65 and c-Rel, two latter being constituents of NF-kappa B regulatory complex. The data demonstrate that besides its traditional target, i.e. newly synthesized or abnormal polypeptides, Hsp70 is able to bind mature, active proteins.
Guzhova
I V
IV
Institute of Cytology RAS, St. Petersburg. guzhova@link.cytspb.rssi.ru
Margulis
B A
BA
D002846:Chromatography, Affinity; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D006358:Hot Temperature; D006801:Humans; D015151:Immunoblotting; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D020298:U937 Cells
D018840:HSP70 Heat-Shock Proteins; D014409:Tumor Necrosis Factor-alpha; D013755:Tetradecanoylphorbol Acetate