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: Jacqueline C Shultz, Ngoc Vu, Michael D Shultz, Mba-Uzoma U Mba, Brian A Shapiro, Charles E Chalfant
• Journal: Molecular cancer research : MCR (Mol Cancer Res) Vol. 10 Issue 5 Pg. 660-9 (May 2012) ISSN: 1557-3125 [Electronic] United States
• PMID: 22522453 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• 2-(1-(3-dimethylaminopropyl)-5-methoxyindol-3-yl)-3-(1H-indol-3-yl)maleimide
• Ceramides
• Chromones
• Indoles
• Isoenzymes
• MAS1 protein, human
• Maleimides
• Morpholines
• Phosphoinositide-3 Kinase Inhibitors
• Phosphoproteins
• Proto-Oncogene Mas
• RNA Splice Sites
• RNA Splicing Factors
• RNA, Small Interfering
• Ribonucleoprotein, U2 Small Nuclear
• SF3B1 protein, human
• bcl-X Protein
• 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
• Protein Kinase C
• protein kinase C lambda

Topics

• Alternative Splicing
• Apoptosis (genetics)
• Carcinoma, Non-Small-Cell Lung (genetics, metabolism)
• Cell Line, Tumor
• Cell Survival
• Ceramides (metabolism)
• Chromones (pharmacology)
• Gene Expression Regulation, Neoplastic
• Humans
• Indoles (pharmacology)
• Isoenzymes (antagonists & inhibitors, genetics, metabolism)
• Maleimides (pharmacology)
• Morpholines (pharmacology)
• Phosphatidylinositol 3-Kinases (metabolism)
• Phosphoinositide-3 Kinase Inhibitors
• Phosphoproteins (genetics, metabolism)
• Protein Kinase C (antagonists & inhibitors, genetics, metabolism)
• Proto-Oncogene Mas
• RNA Splice Sites (genetics)
• RNA Splicing Factors
• RNA, Small Interfering
• Ribonucleoprotein, U2 Small Nuclear (genetics, metabolism)
• Signal Transduction
• bcl-X Protein (genetics, metabolism)