Heat shock stress induces cleavage and activation of PAK2 in apoptotic cells.
Heat shock induces a stress response in mammalian cells and can also lead to apoptotic cell death. Here we report that a 36-kDa myelin basic protein (MBP) kinase detected by an in-gel kinase assay can be drastically activated in several cell types by heat shock. Immunoblot analysis revealed that this 36-kDa MBP kinase can be recognized by an antibody against the C-terminal region of a family of p21Cdc42/Rac-activated kinases (PAKs). By using this antibody and a PAK2-specific antibody against the N-terminal region of PAK2 as tools, we further demonstrated that heat shock can induce cleavage of PAK2 to generate a 36-kDa C-terminal catalytic fragment in mouse Balb/c 3T3 and human Hep 3B cells. The kinetic profile of appearance of the 36-kDa C-terminal catalytic fragment of PAK2 matched exactly with the activation of the 36-kDa MBP kinase in these cells induced by heat shock. In addition, the heat shock-induced cleavage and activation of PAK2 was found to be closely associated with both DNA fragmentation and activation of an ICE/CED-3 family cysteine protease termed caspase-3 in heat shock-treated Hep 3B cells. Moreover, blockage of the activation of caspase-3 by pretreating the cells with two specific tetrapeptidic inhibitors of caspases (Ac-DEVD-cho and Ac-YVAD-cmk) could substantially diminish the extent of heat shock-induced cleavage/activation of PAK2. Overall, our results point out that PAK2 is cleaved and activated during the heat shock-induced apoptotic cell death process and suggest that caspase-3 is involved in this process.
Department of Life Sciences, National Tsing Hua University, Taiwan, ROC.
W H
WH
Chan
J S
JS
Yu
S D
SD
Yang
D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis; D004789:Enzyme Activation; D018869:Heat-Shock Response; D006801:Humans; D006868:Hydrolysis; D051379:Mice; D008807:Mice, Inbred BALB C; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D054462:p21-Activated Kinases
C515907:PAK2 protein, human; C515909:Pak2 protein, mouse; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases