Limits...
The two SAMP repeats and their phosphorylation state in Drosophila Adenomatous polyposis coli-2 play mechanistically distinct roles in negatively regulating Wnt signaling.

Kunttas-Tatli E, Von Kleeck RA, Greaves BD, Vinson D, Roberts DM, McCartney BM - Mol. Biol. Cell (2015)

Bottom Line: One set of motifs frequently lost in these cancer-associated truncations is the SAMP repeats that mediate interactions between APC and Axin.In addition, we demonstrate that the phosphorylation of SAMP repeats is a potential mechanism to regulate their activity.Overall our findings support a model in which each SAMP repeat plays a mechanistically distinct role but they cooperate for maximal destruction complex function.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213.

No MeSH data available.


Related in: MedlinePlus

Phosphorylation of both SAMP1 and SAMP2 plays important roles in destructosome activity in the Drosophila embryo. (A, B) Hatch rate and cuticle analysis of APC2 APC1 double- (APC2g10APC1Q8) embryos with transgenes expressing APC2-FL and SAMP phosphomutants. (B, C) The cuticle phenotypes of embryos that failed to hatch were assessed, and the phenotypic average (PA) was calculated for mutant embryos. Cuticles were classified as either MZ+ (maternally mutant but zygotically rescued) or MZ (maternally and zygotically mutant). Cuticle images are shown at the same scale. (D) In the single–APC2  mutant, only APC2-S1SA/S2SA appears to have reduced function based on the accumulation of Arm and the expression domain of En. Scale bar, 25 μm.
© Copyright Policy - creative-commons
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4666143&req=5

Figure 7: Phosphorylation of both SAMP1 and SAMP2 plays important roles in destructosome activity in the Drosophila embryo. (A, B) Hatch rate and cuticle analysis of APC2 APC1 double- (APC2g10APC1Q8) embryos with transgenes expressing APC2-FL and SAMP phosphomutants. (B, C) The cuticle phenotypes of embryos that failed to hatch were assessed, and the phenotypic average (PA) was calculated for mutant embryos. Cuticles were classified as either MZ+ (maternally mutant but zygotically rescued) or MZ (maternally and zygotically mutant). Cuticle images are shown at the same scale. (D) In the single–APC2 mutant, only APC2-S1SA/S2SA appears to have reduced function based on the accumulation of Arm and the expression domain of En. Scale bar, 25 μm.

Mentions: Similar to the deletion mutants, we tested the destructosome function of the phosphodeficient SAMP mutants in the APC2 APC1 double- background, and with this more sensitive assay, the significance of SAMP phosphorylation became clear. Phosphodeficient SAMP1 mutant alone (APC2-S1SA/S2+) completely eliminated APC2 activity (Figure 7, A and B), whereas phosphodeficient SAMP2 mutant (APC2-S1+/S2SA) resulted in a largely functional APC2 protein, as evidenced by a higher hatch rate and weaker cuticle phenotypes (Figure 7, A and B). Surprisingly, APC2 without any potential SAMP phosphorylation (APC2-S1SA/S2SA) also has partial function, as its hatch rate and cuticle phenotypes more closely matched those of the SAMP2 phosphorylation mutant (Figure 7, A and B). Collectively these findings reveal a surprising interplay between phosphorylation of the SAMP motifs. SAMP1 phosphorylation is required for APC2 destructosome activity, but the observation that blocking SAMP2 phosphorylation mitigates the effect of loss of SAMP1 phosphorylation suggests that there is mechanistic cross-talk between the two SAMP repeats that is mediated by phosphorylation.


The two SAMP repeats and their phosphorylation state in Drosophila Adenomatous polyposis coli-2 play mechanistically distinct roles in negatively regulating Wnt signaling.

Kunttas-Tatli E, Von Kleeck RA, Greaves BD, Vinson D, Roberts DM, McCartney BM - Mol. Biol. Cell (2015)

Phosphorylation of both SAMP1 and SAMP2 plays important roles in destructosome activity in the Drosophila embryo. (A, B) Hatch rate and cuticle analysis of APC2 APC1 double- (APC2g10APC1Q8) embryos with transgenes expressing APC2-FL and SAMP phosphomutants. (B, C) The cuticle phenotypes of embryos that failed to hatch were assessed, and the phenotypic average (PA) was calculated for mutant embryos. Cuticles were classified as either MZ+ (maternally mutant but zygotically rescued) or MZ (maternally and zygotically mutant). Cuticle images are shown at the same scale. (D) In the single–APC2  mutant, only APC2-S1SA/S2SA appears to have reduced function based on the accumulation of Arm and the expression domain of En. Scale bar, 25 μm.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4666143&req=5

Figure 7: Phosphorylation of both SAMP1 and SAMP2 plays important roles in destructosome activity in the Drosophila embryo. (A, B) Hatch rate and cuticle analysis of APC2 APC1 double- (APC2g10APC1Q8) embryos with transgenes expressing APC2-FL and SAMP phosphomutants. (B, C) The cuticle phenotypes of embryos that failed to hatch were assessed, and the phenotypic average (PA) was calculated for mutant embryos. Cuticles were classified as either MZ+ (maternally mutant but zygotically rescued) or MZ (maternally and zygotically mutant). Cuticle images are shown at the same scale. (D) In the single–APC2 mutant, only APC2-S1SA/S2SA appears to have reduced function based on the accumulation of Arm and the expression domain of En. Scale bar, 25 μm.
Mentions: Similar to the deletion mutants, we tested the destructosome function of the phosphodeficient SAMP mutants in the APC2 APC1 double- background, and with this more sensitive assay, the significance of SAMP phosphorylation became clear. Phosphodeficient SAMP1 mutant alone (APC2-S1SA/S2+) completely eliminated APC2 activity (Figure 7, A and B), whereas phosphodeficient SAMP2 mutant (APC2-S1+/S2SA) resulted in a largely functional APC2 protein, as evidenced by a higher hatch rate and weaker cuticle phenotypes (Figure 7, A and B). Surprisingly, APC2 without any potential SAMP phosphorylation (APC2-S1SA/S2SA) also has partial function, as its hatch rate and cuticle phenotypes more closely matched those of the SAMP2 phosphorylation mutant (Figure 7, A and B). Collectively these findings reveal a surprising interplay between phosphorylation of the SAMP motifs. SAMP1 phosphorylation is required for APC2 destructosome activity, but the observation that blocking SAMP2 phosphorylation mitigates the effect of loss of SAMP1 phosphorylation suggests that there is mechanistic cross-talk between the two SAMP repeats that is mediated by phosphorylation.

Bottom Line: One set of motifs frequently lost in these cancer-associated truncations is the SAMP repeats that mediate interactions between APC and Axin.In addition, we demonstrate that the phosphorylation of SAMP repeats is a potential mechanism to regulate their activity.Overall our findings support a model in which each SAMP repeat plays a mechanistically distinct role but they cooperate for maximal destruction complex function.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213.

No MeSH data available.


Related in: MedlinePlus