ORIGINAL PAPER Overexpression of CREB protein protects from tunicamycin-induced apoptosis in various rat cell types Andra ´s Balogh • Ma ´ria Ne ´meth • Ibolya Kolosza ´r • Lajos Marko ´ • Lukasz Przybyl • Kazushi Jinno • Csilla Szigeti • Marija Heffer • Matthias Gebhardt • Jo ´zsef Szebere ´nyi • Dominik N. Mu ¨ ller • Gyo ¨rgy Se ´ta ´lo ´ Jr. • Marianna Pap Ó Springer Science+Business Media New York 2014 Abstract Endoplasmic reticulum (ER) stress plays an essential role in unfolded protein response induced apop- tosis contributing to several pathological conditions. Gly- cogen synthase kinase-3b (GSK-3b) plays a central role in several apoptotic signaling, including ER stress, as the active form of GSK-3b induces apoptosis. The phosphor- ylation of cAMP responsive element (CRE) binding protein (CREB) Ser-133 (S133) residue is the end-point of various signaling pathways, like growth factor signaling, while the Ser-129 (S129) residue is phosphorylated by GSK-3b. The significance of the ubiquitously expressed transcription factor CREB is demonstrated in prolonged, tunicamycin (TM)-induced ER stress in this study. In the experiments wild-type (wt) CREB, S129Ala, S133Ala or S129Ala– S133Ala mutant CREB expressing PC12 rat pheochromo- cytoma cell lines showed increased survival under TM- evoked prolonged ER stress compared to wtPC12 cells. After TM treatment ER stress was activated in all PC12 cell types. Lithium and SB-216763, the selective, well- known inhibitors of GSK-3b, decreased TM-induced apoptosis and promoted cell survival. The proapoptotic BH3-only Bcl-2 family member Bcl-2-interacting mediator of cell death (Bim) level was decreased in the different CREB overexpressing PC12 cells as a result of TM treat- ment. CREB overexpression also inhibited the sequestra- tion of Bim protein from tubulin molecules, as it was demonstrated in wtPC12 cells. Transient expression of wtCREB diminished TM-induced apoptosis in wtPC12, Rat-1 and primary rat vascular smooth muscle cells. These findings demonstrate a novel role of CREB in different cell types as a potent protector against ER stress. Keywords Apoptosis Á ER stress Á Unfolded protein response Á Tunicamycin Á CREB Á PC12 cells Introduction The endoplasmic reticulum (ER) takes part in the synthesis, folding and posttranslational modifications of secretory proteins. Correctly folded proteins leave the ER heading towards the Golgi apparatus. If protein folding is disturbed, unfolded or misfolded protein molecules are retained in the ER and are subject to degradation by the proteasome- dependent ER-associated protein degradation (ERAD) pathway or by autophagy [1]. Physiological or pathological processes can disturb protein folding in the ER lumen are referred to as ER stress, and signaling pathways responding to ER stress are termed the unfolded protein response, UPR Electronic supplementary material The online version of this article (doi:10.1007/s10495-014-0986-z) contains supplementary material, which is available to authorized users. A. Balogh Á M. Ne ´meth Á I. Kolosza ´r Á K. Jinno Á C. Szigeti Á J. Szebere ´nyi Á G. Se ´ta ´lo ´ Jr. Á M. Pap (&) Department of Medical Biology, University of Pe ´cs Medical School, Szigeti 12, Pecs 7624, Hungary e-mail: marianna.pap@aok.pte.hu A. Balogh Á M. Ne ´meth Á I. Kolosza ´r Á K. Jinno Á C. Szigeti Á J. Szebere ´nyi Á G. Se ´ta ´lo ´ Jr. Á M. Pap Signal Transduction Research Group, University of Pe ´cs Ja ´nos Szenta ´gothai Research Centre, Ifju ´sa ´g u ´tja 20, Pecs 7624, Hungary L. Marko ´ Á L. Przybyl Á M. Gebhardt Á D. N. Mu ¨ller Experimental and Clinical Research Center, Charite ´ Medical Faculty and Max-Delbru ¨ck Center for Molecular Medicine, Berlin, Germany M. Heffer Department of Medical Biology, Josip Juraj Strossmayer University of Osijek, Osijek, Croatia 123 Apoptosis DOI 10.1007/s10495-014-0986-z