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Expression of the RAI gene is conducive to apoptosis: studies of induction and interference

Magdalena J Laska1, Dorthe Strandbygård, Anette Kjeldgaard

  • 1Institute of Human Genetics, Bartholin Building, University of Aarhus, DK-8000 Aarhus C, Denmark.

Experimental Cell Research
|June 16, 2007
PubMed

Insights

The RAI gene (PPP1R13L) is upregulated during apoptosis in non-transformed cells. Inhibiting RAI reduces apoptosis, suggesting its necessity in this process, potentially via NF-kappaB signaling.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • The RAI gene, also known as iASPP and PPP1R13L, is implicated in cancer development.
  • Previous speculation suggested RAI's role in apoptosis regulation, either by inducing it via NF-kappaB inhibition or inhibiting it via p53 interaction.
  • RAI's influence on precancerous lesion survival is a key area of interest.

Purpose of the Study:

  • To investigate the role of RAI gene expression in apoptosis.
  • To determine the relationship between RAI induction and apoptosis in non-transformed cells.
  • To elucidate the signaling pathways, particularly NF-kappaB, involved in RAI-mediated apoptosis.

Main Methods:

  • Quantification of RAI mRNA and protein expression in lymphocytes and fibroblasts undergoing apoptosis induced by etoposide, calcium ions, or cytokine/serum deprivation.
  • Utilized small interfering RNA (siRNA) to inhibit RAI expression and assess its impact on apoptosis.
  • Investigated the effect of sulfasalazine, an NF-kappaB inhibitor, on apoptosis in the context of RAI inhibition.
  • Examined RAI expression and apoptosis association in the transformed HEK-293 cell line.

Main Results:

  • RAI mRNA expression increased in non-transformed lymphocytes and fibroblasts upon induction of apoptosis through various stimuli.
  • Etoposide treatment elevated RAI protein levels and promoted its nuclear translocation.
  • siRNA-mediated inhibition of RAI expression significantly reduced apoptosis in these cells.
  • The dependence of apoptosis on RAI was alleviated by treatment with the NF-kappaB inhibitor sulfasalazine.
  • The link between RAI induction and apoptosis appeared disrupted in the transformed HEK-293 cell line.

Conclusions:

  • RAI induction is a necessary, but not sufficient, event for apoptosis in non-transformed cells.
  • The findings support a model where RAI plays a crucial role in initiating apoptosis, likely through an NF-kappaB-mediated mechanism.
  • The altered association in transformed cells suggests dysregulation of this pathway in cancer.

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