title: The Proto-oncogene PKCι regulates the alternative splicing of Bcl-x pre-mRNA.
abstract: Two splice variants derived from the Bcl-x gene via alternative 5' splice site selection (5'SS) are proapoptotic Bcl-x(s) and antiapoptotic Bcl-x(L). Previously, our laboratory showed that apoptotic signaling pathways regulated the alternative 5'SS selection via protein phosphatase-1 and de novo ceramide. In this study, we examined the elusive prosurvival signaling pathways that regulate the 5'SS selection of Bcl-x pre-mRNA in cancer cells. Taking a broad-based approach by using a number of small-molecule inhibitors of various mitogenic/survival pathways, we found that only treatment of non-small cell lung cancer (NSCLC) cell lines with the phosphoinositide 3-kinase (PI3K) inhibitor LY294002 (50 μmol/L) or the pan-protein kinase C (PKC) inhibitor Gö6983 (25 μmol/L) decreased the Bcl-x(L)/(s) mRNA ratio. Pan-PKC inhibitors that did not target the atypical PKCs, PKCι and PKCζ, had no effect on the Bcl-x(L)/(s) mRNA ratio. Additional studies showed that downregulation of the proto-oncogene, PKCι, in contrast to PKCζ, also resulted in a decrease in the Bcl-x(L)/(s) mRNA ratio. Furthermore, downregulation of PKCι correlated with a dramatic decrease in the expression of SAP155, an RNA trans-acting factor that regulates the 5'SS selection of Bcl-x pre-mRNA. Inhibition of the PI3K or atypical PKC pathway induced a dramatic loss of SAP155 complex formation at ceramide-responsive RNA cis-element 1. Finally, forced expression of Bcl-x(L) "rescued" the loss of cell survival induced by PKCι siRNA. In summary, the PI3K/PKCι regulates the alternative splicing of Bcl-x pre-mRNA with implications in the cell survival of NSCLC cells.
authors.affiliation: Department of Biochemistry and Molecular Biology, Virginia Commonwealth University-School of Medicine, Room 2-016, Sanger Hall, 1101 East Marshall Street, P.O. Box 980614, Richmond, VA 23298, USA.
authors.forename: Jacqueline C
authors.initials: JC
authors.lastname: Shultz
authors.forename: Ngoc
authors.initials: N
authors.lastname: Vu
authors.forename: Michael D
authors.initials: MD
authors.lastname: Shultz
authors.forename: Mba-Uzoma U
authors.initials: MU
authors.lastname: Mba
authors.forename: Brian A
authors.initials: BA
authors.lastname: Shapiro
authors.forename: Charles E
authors.initials: CE
authors.lastname: Chalfant
mesh_terms: D017398:Alternative Splicing; D017209:Apoptosis / Q000235:genetics; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival; D002518:Ceramides / Q000378:metabolism; D002867:Chromones / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008301:Maleimides / Q000494:pharmacology; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000090063:Proto-Oncogene Mas; D022821:RNA Splice Sites / Q000235:genetics; D000072260:RNA Splicing Factors; D034741:RNA, Small Interfering; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism; D000099293:Protein Kinase C-lambda
chemical_list: D002518:Ceramides; D002867:Chromones; D007211:Indoles; D007527:Isoenzymes; D008301:Maleimides; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins; D011493:Protein Kinase C; D000090063:Proto-Oncogene Mas; D022821:RNA Splice Sites; D000072260:RNA Splicing Factors; D034741:RNA, Small Interfering; D017413:Ribonucleoprotein, U2 Small Nuclear; D051020:bcl-X Protein; D000099293:Protein Kinase C-lambda; C465664:2-(1-(3-dimethylaminopropyl)-5-methoxyindol-3-yl)-3-(1H-indol-3-yl)maleimide; C000715470:MAS1 protein, human; C112491:SF3B1 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one