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The Proto-oncogene PKCι regulates the alternative splicing of Bcl-x pre-mRNA

Jacqueline C Shultz1, Ngoc Vu, Michael D Shultz

  • 1Department 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.

Molecular Cancer Research : MCR
|April 24, 2012
PubMed

Insights

Prosurvival pathways regulate Bcl-x alternative splicing in non-small cell lung cancer (NSCLC). Phosphoinositide 3-kinase (PI3K) and protein kinase C iota (PKCι) signaling impact Bcl-x mRNA splicing and cell survival.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Cell Signaling

Background:

  • Alternative 5' splice site selection of Bcl-x pre-mRNA generates proapoptotic Bcl-x(s) and antiapoptotic Bcl-x(L) isoforms.
  • Previous studies linked apoptotic pathways, protein phosphatase-1, and ceramide to Bcl-x alternative splicing.
  • The prosurvival signaling pathways regulating Bcl-x alternative splicing in cancer remain largely elusive.

Purpose of the Study:

  • To investigate the prosurvival signaling pathways that control the alternative 5' splice site selection of Bcl-x pre-mRNA in non-small cell lung cancer (NSCLC) cells.
  • To elucidate the role of specific kinases, including phosphoinositide 3-kinase (PI3K) and protein kinase C (PKC) isoforms, in regulating Bcl-x splicing.
  • To determine the impact of these signaling pathways on cancer cell survival.

Main Methods:

  • Utilized small-molecule inhibitors targeting various mitogenic/survival pathways, including PI3K and PKC inhibitors.
  • Employed RNA interference (siRNA) to downregulate specific PKC isoforms (PKCι and PKCζ).
  • Assessed Bcl-x(L)/(s) mRNA ratios, expression of RNA trans-acting factors (SAP155), and protein complex formation.

Main Results:

  • Inhibition of PI3K or pan-PKC (specifically targeting PKCι and PKCζ) decreased the Bcl-x(L)/(s) mRNA ratio in NSCLC cells.
  • Downregulation of PKCι, but not PKCζ, reduced the Bcl-x(L)/(s) mRNA ratio and decreased SAP155 expression.
  • PI3K or atypical PKC inhibition disrupted SAP155 complex formation at a specific RNA element, and forced Bcl-x(L) expression rescued PKCι siRNA-induced cell death.

Conclusions:

  • The PI3K/PKCι signaling pathway regulates the alternative splicing of Bcl-x pre-mRNA.
  • This regulation of Bcl-x alternative splicing by PI3K/PKCι has significant implications for the cell survival of non-small cell lung cancer cells.
  • SAP155 acts as a crucial RNA trans-acting factor in this pathway, linking PI3K/PKCι signaling to Bcl-x splicing outcomes.

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