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MAPKAP kinase 2 is activated by heat shock and TNF‐α: In vivo phosphorylation of small heat shock protein results from stimulation of the MAP kinase cascade
Author(s) -
Engel Katrin,
Ahlers Annette,
Brach Marion A.,
Herrmann Friedhelm,
Gaestel Matthias
Publication year - 1995
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.240570216
Subject(s) - kinase , phosphorylation , microbiology and biotechnology , mitogen activated protein kinase kinase , cyclin dependent kinase 2 , protein kinase a , biology , chemistry
The activation of MAPKAP kinase 2 was investigated under heat‐shock conditions in mouse Ehrlich ascites tumor cells and after treatment of human MO7 cells with tumor necrosis factor‐α (TNF‐α). MAPKAP kinase 2 activity was determined using the small heat‐shock proteins (sHsps) Hsp25 and Hsp27 as substrates. In both cell types, about a threefold increase in MAPKAP kinase 2 activity could be detected in a time interval of about 10–15 min after stimulation either by heat shock or TNF‐α. Phosphorylation of MAPKAP kinase 2, but not the level of MAPKAP kinase 2 mRNA, was increased after heat shock in EAT cells. It is further shown that activation of MAPKAP kinase 2 in MO7 cells is accompanied by increased MAP kinase activity. These data strongly suggest that increased phosphorylation of the sHsps after heat shock or TNF‐α treatment results from phosphorylation by MAPKAP kinase 2, which itself is activated by phosphorylation through MAP kinases. Hence, we demonstrate that MAPKAP kinase 2 is responsible not only for phosphorylation of sHsps in vitro but also in vivo. The findings link sHsp phosphorylation to the MAP kinase cascade, explaining the early phosphorylation of sHsp that is stimulated by a variety of inducers such as mitogens, phorbol esters, thrombin, calcium ionophores, and heat shock.