title: Protein kinase C-epsilon regulates the apoptosis and survival of glioma cells.
abstract: In this study, we examined the role of protein kinase C (PKC)-epsilon in the apoptosis and survival of glioma cells using tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-stimulated cells and silencing of PKCepsilon expression. Treatment of glioma cells with TRAIL induced activation, caspase-dependent cleavage, and down-regulation of PKCepsilon within 3 to 5 hours of treatment. Overexpression of PKCepsilon inhibited the apoptosis induced by TRAIL, acting downstream of caspase 8 and upstream of Bid cleavage and cytochrome c release from the mitochondria. A caspase-resistant PKCepsilon mutant (D383A) was more protective than PKCepsilon, suggesting that both the cleavage of PKCepsilon and its down-regulation contributed to the apoptotic effect of TRAIL. To further study the role of PKCepsilon in glioma cell apoptosis, we employed short interfering RNAs directed against the mRNA of PKCepsilon and found that silencing of PKCepsilon expression induced apoptosis of various glioma cell lines and primary glioma cultures. To delineate the molecular mechanisms involved in the apoptosis induced by silencing of PKCepsilon, we examined the expression and phosphorylation of various apoptosis-related proteins. We found that knockdown of PKCepsilon did not affect the expression of Bcl2 and Bax or the phosphorylation and expression of Erk1/2, c-Jun-NH2-kinase, p38, or STAT, whereas it selectively reduced the expression of AKT. Similarly, TRAIL reduced the expression of AKT in glioma cells and this decrease was abolished in cells overexpressing PKCepsilon. Our results suggest that the cleavage of PKCepsilon and its down-regulation play important roles in the apoptotic effect of TRAIL. Moreover, PKCepsilon regulates AKT expression and is essential for the survival of glioma cells.
authors.affiliation: Gonda (Goldschmied) Medical Diagnosis Research Center, Faculty of Life-Sciences, Bar-Ilan University, Ramat Gan, Israel.
authors.forename: Hana
authors.initials: H
authors.lastname: Okhrimenko
authors.forename: Wei
authors.initials: W
authors.lastname: Lu
authors.forename: Cunli
authors.initials: C
authors.lastname: Xiang
authors.forename: Nathan
authors.initials: N
authors.lastname: Hamburger
authors.forename: Gila
authors.initials: G
authors.lastname: Kazimirsky
authors.forename: Chaya
authors.initials: C
authors.lastname: Brodie
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D015536:Down-Regulation; D004789:Enzyme Activation / Q000187:drug effects; D020868:Gene Silencing; D005910:Glioma / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D006801:Humans; D008562:Membrane Glycoproteins / Q000494:pharmacology; D008969:Molecular Sequence Data; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D051744:Protein Kinase C-epsilon; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D053221:TNF-Related Apoptosis-Inducing Ligand; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D051017:Apoptosis Regulatory Proteins; D008562:Membrane Glycoproteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C497255:PRKCE protein, human; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; D020169:Caspases