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Drosophila p120catenin plays a supporting role in cell adhesion but is not an essential adherens junction component.

Myster SH, Cavallo R, Anderson CT, Fox DT, Peifer M - J. Cell Biol. (2003)

Bottom Line: We generated alleles of p120 and found that mutants are viable and fertile and have no substantial changes in junction structure or function.However, p120 mutations strongly enhance mutations in the genes encoding DE-cadherin or Armadillo, the beta-catenin homologue.Finally, we examined the localization of p120 during embryogenesis. p120 localizes to adherens junctions, but its localization there is less universal than that of core adherens junction proteins.

View Article: PubMed Central - PubMed

Affiliation: Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.

ABSTRACT
Cadherin-catenin complexes, localized to adherens junctions, are essential for cell-cell adhesion. One means of regulating adhesion is through the juxtamembrane domain of the cadherin cytoplasmic tail. This region is the binding site for p120, leading to the hypothesis that p120 is a key regulator of cell adhesion. p120 has also been suggested to regulate the GTPase Rho and to regulate transcription via its binding partner Kaiso. To test these hypothesized functions, we turned to Drosophila, which has only a single p120 family member. It localizes to adherens junctions and binds the juxtamembrane region of DE-cadherin (DE-cad). We generated alleles of p120 and found that mutants are viable and fertile and have no substantial changes in junction structure or function. However, p120 mutations strongly enhance mutations in the genes encoding DE-cadherin or Armadillo, the beta-catenin homologue. Finally, we examined the localization of p120 during embryogenesis. p120 localizes to adherens junctions, but its localization there is less universal than that of core adherens junction proteins. Together, these data suggest that p120 is an important positive modulator of adhesion but that it is not an essential core component of adherens junctions.

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AJ proteins are not significantly altered in levels or localization in p120 mutants. (A) Embryonic extracts from 3–8 h wild-type (WT) and p120308 (mut) strains immunoblotted with antibodies to p120 (arrowhead), DE-cad, α-cat, and Arm. Anti-Pnut is a loading control. Mol wt standards (kD) are at left. (B–O) Wild-type and p120308 mutant embryos labeled with Arm (B–G), DE-cad (H and I), α-cat (J and K), or phalloidin to show F-actin (L–O). (F, G, N, and O) arrows indicate the leading edge during dorsal closure. Bars, 5 μm.
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fig5: AJ proteins are not significantly altered in levels or localization in p120 mutants. (A) Embryonic extracts from 3–8 h wild-type (WT) and p120308 (mut) strains immunoblotted with antibodies to p120 (arrowhead), DE-cad, α-cat, and Arm. Anti-Pnut is a loading control. Mol wt standards (kD) are at left. (B–O) Wild-type and p120308 mutant embryos labeled with Arm (B–G), DE-cad (H and I), α-cat (J and K), or phalloidin to show F-actin (L–O). (F, G, N, and O) arrows indicate the leading edge during dorsal closure. Bars, 5 μm.

Mentions: To determine the effect of loss of p120 on AJs in more detail, we examined the levels and localization of AJ proteins in p120308mutants compared with wild-type. We immunoblotted cell extracts from wild-type or p120308- mutant embryos with antibodies to DE-cad, α-cat, and Arm (Fig. 5 A). No noticeable changes in levels of these proteins were seen, though we cannot rule out slight changes (less than twofold). We also examined the levels and localization during embryogenesis of Arm (Fig. 5, B–G), DE-cad (Fig. 5, H and I), and α-cat (Fig. 5, J and K), and the localization of actin to the cortex (Fig. 5, L–O) by immunofluorescence confocal microscopy. To control the experiment, we mixed homozygous p120308mutants with wild-type embryos carrying a histone-GFP transgene, fixed and stained them together, and visualized them on the same slide with the same confocal settings. Images were scored blind by two observers, and no consistent difference in either the levels or localization of any AJ proteins or of cortical actin was observed. In each case, a slight preponderance of mutant embryos stained more weakly, but there were no systematic differences, and both wild-type and mutants fell across the spectrum of variation in staining intensity seen among embryos.


Drosophila p120catenin plays a supporting role in cell adhesion but is not an essential adherens junction component.

Myster SH, Cavallo R, Anderson CT, Fox DT, Peifer M - J. Cell Biol. (2003)

AJ proteins are not significantly altered in levels or localization in p120 mutants. (A) Embryonic extracts from 3–8 h wild-type (WT) and p120308 (mut) strains immunoblotted with antibodies to p120 (arrowhead), DE-cad, α-cat, and Arm. Anti-Pnut is a loading control. Mol wt standards (kD) are at left. (B–O) Wild-type and p120308 mutant embryos labeled with Arm (B–G), DE-cad (H and I), α-cat (J and K), or phalloidin to show F-actin (L–O). (F, G, N, and O) arrows indicate the leading edge during dorsal closure. Bars, 5 μm.
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Related In: Results  -  Collection

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fig5: AJ proteins are not significantly altered in levels or localization in p120 mutants. (A) Embryonic extracts from 3–8 h wild-type (WT) and p120308 (mut) strains immunoblotted with antibodies to p120 (arrowhead), DE-cad, α-cat, and Arm. Anti-Pnut is a loading control. Mol wt standards (kD) are at left. (B–O) Wild-type and p120308 mutant embryos labeled with Arm (B–G), DE-cad (H and I), α-cat (J and K), or phalloidin to show F-actin (L–O). (F, G, N, and O) arrows indicate the leading edge during dorsal closure. Bars, 5 μm.
Mentions: To determine the effect of loss of p120 on AJs in more detail, we examined the levels and localization of AJ proteins in p120308mutants compared with wild-type. We immunoblotted cell extracts from wild-type or p120308- mutant embryos with antibodies to DE-cad, α-cat, and Arm (Fig. 5 A). No noticeable changes in levels of these proteins were seen, though we cannot rule out slight changes (less than twofold). We also examined the levels and localization during embryogenesis of Arm (Fig. 5, B–G), DE-cad (Fig. 5, H and I), and α-cat (Fig. 5, J and K), and the localization of actin to the cortex (Fig. 5, L–O) by immunofluorescence confocal microscopy. To control the experiment, we mixed homozygous p120308mutants with wild-type embryos carrying a histone-GFP transgene, fixed and stained them together, and visualized them on the same slide with the same confocal settings. Images were scored blind by two observers, and no consistent difference in either the levels or localization of any AJ proteins or of cortical actin was observed. In each case, a slight preponderance of mutant embryos stained more weakly, but there were no systematic differences, and both wild-type and mutants fell across the spectrum of variation in staining intensity seen among embryos.

Bottom Line: We generated alleles of p120 and found that mutants are viable and fertile and have no substantial changes in junction structure or function.However, p120 mutations strongly enhance mutations in the genes encoding DE-cadherin or Armadillo, the beta-catenin homologue.Finally, we examined the localization of p120 during embryogenesis. p120 localizes to adherens junctions, but its localization there is less universal than that of core adherens junction proteins.

View Article: PubMed Central - PubMed

Affiliation: Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.

ABSTRACT
Cadherin-catenin complexes, localized to adherens junctions, are essential for cell-cell adhesion. One means of regulating adhesion is through the juxtamembrane domain of the cadherin cytoplasmic tail. This region is the binding site for p120, leading to the hypothesis that p120 is a key regulator of cell adhesion. p120 has also been suggested to regulate the GTPase Rho and to regulate transcription via its binding partner Kaiso. To test these hypothesized functions, we turned to Drosophila, which has only a single p120 family member. It localizes to adherens junctions and binds the juxtamembrane region of DE-cadherin (DE-cad). We generated alleles of p120 and found that mutants are viable and fertile and have no substantial changes in junction structure or function. However, p120 mutations strongly enhance mutations in the genes encoding DE-cadherin or Armadillo, the beta-catenin homologue. Finally, we examined the localization of p120 during embryogenesis. p120 localizes to adherens junctions, but its localization there is less universal than that of core adherens junction proteins. Together, these data suggest that p120 is an important positive modulator of adhesion but that it is not an essential core component of adherens junctions.

Show MeSH
Related in: MedlinePlus