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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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p120 localization during the syncytial development and cellularization differs from that of Arm. (A–J) Syncytial blastoderm (A and B) and cellularizing embryos (C–J). p120 (red); Arm (green). (A–D, G, and H) Surface sections. (E, F, I, and J) Optical cross sections. (A and B) Arm localizes strongly to pseudocleavage furrows, whereas p120 staining is much less intense (arrow). (C–F) Early cellularization. p120 colocalizes with Arm at basal junctions (E and F, arrows) and also stains paired structures in the cytoplasm (C and D, arrows). (G–J) Mid-late cellularization. p120 is reduced at cell junctions (H, arrow) compared with Arm (G). Arm labels basal junctions, lateral membranes, and nascent AJs (I). p120 localizes to an apical domain (J, arrow). (K–M and O–S) Embryos expressing p120-GFP. (K–M) Live images, cellularization. p120-GFP localizes to basal junctions (K and M, arrowhead), nascent AJs (L), and centrosomes (L and M arrows). (N) Syncytial embryo, rabbit anti-p120. (O and P) p120-GFP (green), propidium iodide to label DNA (red), γ-tubulin (gtub, blue). p120-GFP and γ-tubulin colocalize (arrow) and p120-GFP is on mitotic spindles (arrowhead). (Q–S) p120-GFP (green); centrosomin (cnn, red). p120-GFP is enriched at cell junctions (arrowhead) and with condensing DNA (black arrow), and colocalizes with centrosomin (white arrow). Centrosomal p120-GFP is absent by stage 9 (S). Bars, 5 μm.
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fig8: p120 localization during the syncytial development and cellularization differs from that of Arm. (A–J) Syncytial blastoderm (A and B) and cellularizing embryos (C–J). p120 (red); Arm (green). (A–D, G, and H) Surface sections. (E, F, I, and J) Optical cross sections. (A and B) Arm localizes strongly to pseudocleavage furrows, whereas p120 staining is much less intense (arrow). (C–F) Early cellularization. p120 colocalizes with Arm at basal junctions (E and F, arrows) and also stains paired structures in the cytoplasm (C and D, arrows). (G–J) Mid-late cellularization. p120 is reduced at cell junctions (H, arrow) compared with Arm (G). Arm labels basal junctions, lateral membranes, and nascent AJs (I). p120 localizes to an apical domain (J, arrow). (K–M and O–S) Embryos expressing p120-GFP. (K–M) Live images, cellularization. p120-GFP localizes to basal junctions (K and M, arrowhead), nascent AJs (L), and centrosomes (L and M arrows). (N) Syncytial embryo, rabbit anti-p120. (O and P) p120-GFP (green), propidium iodide to label DNA (red), γ-tubulin (gtub, blue). p120-GFP and γ-tubulin colocalize (arrow) and p120-GFP is on mitotic spindles (arrowhead). (Q–S) p120-GFP (green); centrosomin (cnn, red). p120-GFP is enriched at cell junctions (arrowhead) and with condensing DNA (black arrow), and colocalizes with centrosomin (white arrow). Centrosomal p120-GFP is absent by stage 9 (S). Bars, 5 μm.

Mentions: We next compared the localization of p120 at different developmental stages to that of the core AJ protein Arm. p120 accumulates at cell–cell borders through most of embryogenesis, largely paralleling Arm and DE-cad. However, some intriguing differences were observed. p120 is not as highly enriched in junctional structures during early stages of embryogenesis as are core AJ proteins. In early Drosophila development, 13 rounds of nuclear division occur without cytokinesis. The last three occur at the egg cortex, and during mitosis transient membrane invaginations called pseudocleavage furrows separate each spindle from the others. Arm, α-cat, and DE-cad localize to pseudocleavage furrows (McCartney et al., 2001) (Fig. 8 A). In contrast, p120 localization to pseudocleavage furrows was very weak (Fig. 8, A and B). During cellularization, which ends the syncytial phase, Arm and DE-cad localize to basal junctions just behind the advancing contractile apparatus and later localize to nascent AJs (for review see Tepass et al., 2001). Endogenous p120 colocalizes with Arm to basal junctions at early cellularization (Fig. 8, C–F) but at mid-late cellularization p120 is only weakly detectable at junctional structures (Fig. 8, G–H). Instead, p120 accumulates in the apical cytoplasm (Fig. 8, I and J, arrow). Thus, p120 is not as prominent a component of all early junctional structures as are core AJ proteins. Interestingly, when we expressed p120-GFP in early embryos (probably at levels exceeding endogenous p120), it localized to pseudocleavage furrows, basal junctions, and nascent AJs (Fig. 8, K–M; unpublished data).


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)

p120 localization during the syncytial development and cellularization differs from that of Arm. (A–J) Syncytial blastoderm (A and B) and cellularizing embryos (C–J). p120 (red); Arm (green). (A–D, G, and H) Surface sections. (E, F, I, and J) Optical cross sections. (A and B) Arm localizes strongly to pseudocleavage furrows, whereas p120 staining is much less intense (arrow). (C–F) Early cellularization. p120 colocalizes with Arm at basal junctions (E and F, arrows) and also stains paired structures in the cytoplasm (C and D, arrows). (G–J) Mid-late cellularization. p120 is reduced at cell junctions (H, arrow) compared with Arm (G). Arm labels basal junctions, lateral membranes, and nascent AJs (I). p120 localizes to an apical domain (J, arrow). (K–M and O–S) Embryos expressing p120-GFP. (K–M) Live images, cellularization. p120-GFP localizes to basal junctions (K and M, arrowhead), nascent AJs (L), and centrosomes (L and M arrows). (N) Syncytial embryo, rabbit anti-p120. (O and P) p120-GFP (green), propidium iodide to label DNA (red), γ-tubulin (gtub, blue). p120-GFP and γ-tubulin colocalize (arrow) and p120-GFP is on mitotic spindles (arrowhead). (Q–S) p120-GFP (green); centrosomin (cnn, red). p120-GFP is enriched at cell junctions (arrowhead) and with condensing DNA (black arrow), and colocalizes with centrosomin (white arrow). Centrosomal p120-GFP is absent by stage 9 (S). Bars, 5 μm.
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fig8: p120 localization during the syncytial development and cellularization differs from that of Arm. (A–J) Syncytial blastoderm (A and B) and cellularizing embryos (C–J). p120 (red); Arm (green). (A–D, G, and H) Surface sections. (E, F, I, and J) Optical cross sections. (A and B) Arm localizes strongly to pseudocleavage furrows, whereas p120 staining is much less intense (arrow). (C–F) Early cellularization. p120 colocalizes with Arm at basal junctions (E and F, arrows) and also stains paired structures in the cytoplasm (C and D, arrows). (G–J) Mid-late cellularization. p120 is reduced at cell junctions (H, arrow) compared with Arm (G). Arm labels basal junctions, lateral membranes, and nascent AJs (I). p120 localizes to an apical domain (J, arrow). (K–M and O–S) Embryos expressing p120-GFP. (K–M) Live images, cellularization. p120-GFP localizes to basal junctions (K and M, arrowhead), nascent AJs (L), and centrosomes (L and M arrows). (N) Syncytial embryo, rabbit anti-p120. (O and P) p120-GFP (green), propidium iodide to label DNA (red), γ-tubulin (gtub, blue). p120-GFP and γ-tubulin colocalize (arrow) and p120-GFP is on mitotic spindles (arrowhead). (Q–S) p120-GFP (green); centrosomin (cnn, red). p120-GFP is enriched at cell junctions (arrowhead) and with condensing DNA (black arrow), and colocalizes with centrosomin (white arrow). Centrosomal p120-GFP is absent by stage 9 (S). Bars, 5 μm.
Mentions: We next compared the localization of p120 at different developmental stages to that of the core AJ protein Arm. p120 accumulates at cell–cell borders through most of embryogenesis, largely paralleling Arm and DE-cad. However, some intriguing differences were observed. p120 is not as highly enriched in junctional structures during early stages of embryogenesis as are core AJ proteins. In early Drosophila development, 13 rounds of nuclear division occur without cytokinesis. The last three occur at the egg cortex, and during mitosis transient membrane invaginations called pseudocleavage furrows separate each spindle from the others. Arm, α-cat, and DE-cad localize to pseudocleavage furrows (McCartney et al., 2001) (Fig. 8 A). In contrast, p120 localization to pseudocleavage furrows was very weak (Fig. 8, A and B). During cellularization, which ends the syncytial phase, Arm and DE-cad localize to basal junctions just behind the advancing contractile apparatus and later localize to nascent AJs (for review see Tepass et al., 2001). Endogenous p120 colocalizes with Arm to basal junctions at early cellularization (Fig. 8, C–F) but at mid-late cellularization p120 is only weakly detectable at junctional structures (Fig. 8, G–H). Instead, p120 accumulates in the apical cytoplasm (Fig. 8, I and J, arrow). Thus, p120 is not as prominent a component of all early junctional structures as are core AJ proteins. Interestingly, when we expressed p120-GFP in early embryos (probably at levels exceeding endogenous p120), it localized to pseudocleavage furrows, basal junctions, and nascent AJs (Fig. 8, K–M; unpublished data).

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