Limits...
The Drosophila sterile-20 kinase slik controls cell proliferation and apoptosis during imaginal disc development.

Hipfner DR, Cohen SM - PLoS Biol. (2003)

Bottom Line: Tumor-like tissue overgrowth results when apoptosis is prevented.Activation of Raf can compensate for the lack of Slik and support cell survival, but activation of ERK cannot.We suggest that Slik mediates growth and survival cues to promote cell proliferation and control cell survival during Drosophila development.

View Article: PubMed Central - PubMed

Affiliation: European Molecular Biology Laboratory, Heidelberg, Germany.

ABSTRACT
Cell proliferation and programmed cell death are closely controlled during animal development. Proliferative stimuli generally also induce apoptosis, and anti-apoptotic factors are required to allow net cell proliferation. Genetic studies in Drosophila have led to identification of a number of genes that control both processes, providing new insights into the mechanisms that coordinate cell growth, proliferation, and death during development and that fail to do so in diseases of cell proliferation. We present evidence that the Drosophila Sterile-20 kinase Slik promotes cell proliferation and controls cell survival. At normal levels, Slik provides survival cues that prevent apoptosis. Cells deprived of Slik activity can grow, divide, and differentiate, but have an intrinsic survival defect and undergo apoptosis even under conditions in which they are not competing with normal cells for survival cues. Like some oncogenes, excess Slik activity stimulates cell proliferation, but this is compensated for by increased cell death. Tumor-like tissue overgrowth results when apoptosis is prevented. We present evidence that Slik acts via Raf, but not via the canonical ERK pathway. Activation of Raf can compensate for the lack of Slik and support cell survival, but activation of ERK cannot. We suggest that Slik mediates growth and survival cues to promote cell proliferation and control cell survival during Drosophila development.

Show MeSH
Slik Binds to Raf(Right) Endogenous Slik protein, or transfected Slik or Slikkd proteins were immunoprecipitated from S2 cells with anti-Slik. (Left) The blot was probed with anti-Myc to visualize co-precipitation of Myc-tagged Raf.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC261876&req=5

pbio.0000035-g011: Slik Binds to Raf(Right) Endogenous Slik protein, or transfected Slik or Slikkd proteins were immunoprecipitated from S2 cells with anti-Slik. (Left) The blot was probed with anti-Myc to visualize co-precipitation of Myc-tagged Raf.

Mentions: The strong genetic interactions between Slik and Raf prompted us to ask whether Slik can bind directly to Raf. Co-immunoprecipitation experiments were performed using S2 cells transfected to express Myc-tagged Raf. Immunoprecipitation of endogenous Slik protein from S2 cells was able to coprecipitate Raf (Figure 11, lane 6; the loading control represents 25% of input). Cotransfection of S2 cells to express Slik or the kinase inactive Slikkd increased the recovery of Raf in the coimmunoprecipitation (Figure 11, lanes 4 and 5). The relationship between Slik and Raf resembles that reported for the Ste20 kinase germinal center kinase (GCK) and the MAP3K MEKK1 in that GCK binds to MEKK1 and activates it in a kinase-independent manner (Chadee et al. 2002). Our results suggest that activation of Raf is mediated by binding to Slik, rather than by phosphorylation of Raf by Slik. We examined the level of ERK phosphorylation in S2 cells transfected to overexpress Slik or Slikkd. No significant difference was observed (data not shown). Taken together with the finding that expression of activated ERK cannot rescue the slik mutant survival defect in vivo, these findings suggest that Raf does not act via the canonical ERK MAPK pathway to mediate Slik's activity in supporting cell survival and promoting cell proliferation.


The Drosophila sterile-20 kinase slik controls cell proliferation and apoptosis during imaginal disc development.

Hipfner DR, Cohen SM - PLoS Biol. (2003)

Slik Binds to Raf(Right) Endogenous Slik protein, or transfected Slik or Slikkd proteins were immunoprecipitated from S2 cells with anti-Slik. (Left) The blot was probed with anti-Myc to visualize co-precipitation of Myc-tagged Raf.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC261876&req=5

pbio.0000035-g011: Slik Binds to Raf(Right) Endogenous Slik protein, or transfected Slik or Slikkd proteins were immunoprecipitated from S2 cells with anti-Slik. (Left) The blot was probed with anti-Myc to visualize co-precipitation of Myc-tagged Raf.
Mentions: The strong genetic interactions between Slik and Raf prompted us to ask whether Slik can bind directly to Raf. Co-immunoprecipitation experiments were performed using S2 cells transfected to express Myc-tagged Raf. Immunoprecipitation of endogenous Slik protein from S2 cells was able to coprecipitate Raf (Figure 11, lane 6; the loading control represents 25% of input). Cotransfection of S2 cells to express Slik or the kinase inactive Slikkd increased the recovery of Raf in the coimmunoprecipitation (Figure 11, lanes 4 and 5). The relationship between Slik and Raf resembles that reported for the Ste20 kinase germinal center kinase (GCK) and the MAP3K MEKK1 in that GCK binds to MEKK1 and activates it in a kinase-independent manner (Chadee et al. 2002). Our results suggest that activation of Raf is mediated by binding to Slik, rather than by phosphorylation of Raf by Slik. We examined the level of ERK phosphorylation in S2 cells transfected to overexpress Slik or Slikkd. No significant difference was observed (data not shown). Taken together with the finding that expression of activated ERK cannot rescue the slik mutant survival defect in vivo, these findings suggest that Raf does not act via the canonical ERK MAPK pathway to mediate Slik's activity in supporting cell survival and promoting cell proliferation.

Bottom Line: Tumor-like tissue overgrowth results when apoptosis is prevented.Activation of Raf can compensate for the lack of Slik and support cell survival, but activation of ERK cannot.We suggest that Slik mediates growth and survival cues to promote cell proliferation and control cell survival during Drosophila development.

View Article: PubMed Central - PubMed

Affiliation: European Molecular Biology Laboratory, Heidelberg, Germany.

ABSTRACT
Cell proliferation and programmed cell death are closely controlled during animal development. Proliferative stimuli generally also induce apoptosis, and anti-apoptotic factors are required to allow net cell proliferation. Genetic studies in Drosophila have led to identification of a number of genes that control both processes, providing new insights into the mechanisms that coordinate cell growth, proliferation, and death during development and that fail to do so in diseases of cell proliferation. We present evidence that the Drosophila Sterile-20 kinase Slik promotes cell proliferation and controls cell survival. At normal levels, Slik provides survival cues that prevent apoptosis. Cells deprived of Slik activity can grow, divide, and differentiate, but have an intrinsic survival defect and undergo apoptosis even under conditions in which they are not competing with normal cells for survival cues. Like some oncogenes, excess Slik activity stimulates cell proliferation, but this is compensated for by increased cell death. Tumor-like tissue overgrowth results when apoptosis is prevented. We present evidence that Slik acts via Raf, but not via the canonical ERK pathway. Activation of Raf can compensate for the lack of Slik and support cell survival, but activation of ERK cannot. We suggest that Slik mediates growth and survival cues to promote cell proliferation and control cell survival during Drosophila development.

Show MeSH