title: PKC signaling prevents irradiation-induced apoptosis of primary human fibroblasts.
abstract: Primary cells respond to irradiation by activation of the DNA damage response and cell cycle arrest, which eventually leads to senescence or apoptosis. It is not clear in detail which signaling pathways or networks regulate the induction of either apoptosis or senescence. Primary human fibroblasts are able to withstand high doses of irradiation and to prevent irradiation-induced apoptosis. However, the underlying regulatory basis for this phenotype is not well understood. Here, a kinetic network analysis based on reverse phase protein arrays (RPPAs) in combination with extensive western blot and cell culture analyses was employed to decipher the cytoplasmic and nuclear signaling networks and to identify possible antiapoptotic pathways. This analysis identified activation of known DNA damage response pathways (e.g., phosphorylation of MKK3/6, p38, MK2, Hsp27, p53 and Chk1) as well as of prosurvival (e.g., MEK-ERK, cAMP response element-binding protein (CREB), protein kinase C (PKC)) and antiapoptotic markers (e.g., Bad, Bcl-2). Interestingly, PKC family members were activated early upon irradiation, suggesting a regulatory function in the ionizing radiation (IR) response of these cells. Inhibition or downregulation of PKC in primary human fibroblasts caused IR-dependent downregulation of the identified prosurvival (CREB phosphorylation) and antiapoptotic (Bad phosphorylation, Bcl-2) markers and thus lead to a proliferation stop and to apoptosis. Taken together, our analysis suggests that cytoplasmic PKC signaling conditions IR-stressed MRC-5 and IMR-90 cells to prevent irradiation-induced apoptosis. These findings contribute to the understanding of the cellular and nuclear IR response and may thus eventually improve the efficacy of radiotherapy and help overcome tumor radioresistance.
authors: Institute of Veterinary Biochemistry and Molecular Biology (IVBMB), University of Zurich, Winterthurerstrasse 190, Zurich, Switzerland.
authors: A
authors: A
authors: Bluwstein
authors: N
authors: N
authors: Kumar
authors: K
authors: K
authors: Léger
authors: J
authors: J
authors: Traenkle
authors: J van
authors: Jv
authors: Oostrum
authors: H
authors: H
authors: Rehrauer
authors: M
authors: M
authors: Baudis
authors: M O
authors: MO
authors: Hottiger
mesh_terms: D017209:Apoptosis / Q000528:radiation effects*; D050882:CREB-Binding Protein / Q000378:metabolism; D016000:Cluster Analysis; D004249:DNA Damage / Q000528:radiation effects; D004260:DNA Repair; D015536:Down-Regulation; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation; D060066:Protein Interaction Maps; D011493:Protein Kinase C / Q000378:metabolism*; D020543:Proteome / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011839:Radiation, Ionizing; D016160:Retinoblastoma Protein / Q000378:metabolism; D015398:Signal Transduction; D051025:bcl-Associated Death Protein / Q000378:metabolism
chemical_list: D020543:Proteome; D019253:Proto-Oncogene Proteins c-bcl-2; D016160:Retinoblastoma Protein; D051025:bcl-Associated Death Protein; D050882:CREB-Binding Protein; D011493:Protein Kinase C