PT  - JOURNAL ARTICLE
AU  - Daniel Spohn
AU  - Oliver G. Rössler
AU  - Stephan E. Philipp
AU  - Michael Raubuch
AU  - Shigetaka Kitajima
AU  - Désirée Griesemer
AU  - Markus Hoth
AU  - Gerald Thiel
TI  - Thapsigargin Induces Expression of Activating Transcription Factor 3 in Human Keratinocytes Involving Ca<sup>2+</sup> Ions and c-Jun N-Terminal Protein Kinase
AID  - 10.1124/mol.110.067637
DP  - 2010 Nov 01
TA  - Molecular Pharmacology
PG  - 865--876
VI  - 78
IP  - 5
4099  - http://molpharm.aspetjournals.org/content/78/5/865.short
4100  - http://molpharm.aspetjournals.org/content/78/5/865.full
SO  - Mol Pharmacol2010 Nov 01; 78
AB  - Thapsigargin is a specific inhibitor of the sarco/endoplasmic reticulum Ca2+ ATPase of the endoplasmic reticulum. Here, we show that stimulation of human HaCaT keratinocytes with nanomolar concentrations of thapsigargin triggers expression of activating transcription factor (ATF) 3, a basic-region leucin zipper transcription factor. ATF3 expression was also up-regulated in thapsigargin-stimulated glioma cells, hepatoma cells, retinal pigment epithelial cells, and airway epithelial cells. Thapsigargin-induced up-regulation of ATF3 expression in keratinocytes was attenuated by BAPTA-acetoxymethyl ester or by expression of the Ca2+-binding protein parvalbumin in the cytosol of HaCaT cells but not by a panel of pharmacological agents that chelate extracellular Ca2+ (EGTA) or inhibit either ryanodine receptors (dantrolene) or voltage-gated Ca2+ channels (nifedipine). Hence, elevated levels of intracellular Ca2+, released from intracellular stores, are essential for the effect of thapsigargin on the biosynthesis of ATF3. The thapsigargin-induced signaling pathway was blocked by expression of either mitogen-activated protein kinase phosphatase-1 or -5. Experiments involving pharmacological and genetic tools revealed the importance of c-Jun N-terminal protein kinase (JNK) within the signaling cascade, whereas inhibition of extracellular signal-regulated protein kinase or p38 protein kinase did not attenuate thapsigargin-induced expression of ATF3. Functional studies showed that treatment of HaCaT keratinocytes with thapsigargin led to a 2-fold induction of caspase-3/7 activity. The up-regulation of caspase-3/7 activity in thapsigargin-stimulated HaCaT cells was attenuated by inhibition of JNK. Together, these data show that stimulation of HaCaT cells with thapsigargin induces a specific signaling pathway in keratinocytes involving activation of JNK, biosynthesis of ATF3, and up-regulation of caspase-3/7 activity.