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Cdc42 and Par proteins stabilize dynamic adherens junctions in the Drosophila neuroectoderm through regulation of apical endocytosis.

Harris KP, Tepass U - J. Cell Biol. (2008)

Bottom Line: Loss of Cdc42 function caused an increase in the endocytotic uptake of apical proteins, including apical polarity factors such as Crumbs, which are required for AJ stability.The Par complex acts as an effector for Cdc42 in controlling the endocytosis of apical proteins.This study reveals functional interactions between apical polarity proteins and endocytosis that are critical for stabilizing dynamic basolateral AJs.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario M5S 3G5, Canada.

ABSTRACT
Cell rearrangements require dynamic changes in cell-cell contacts to maintain tissue integrity. We investigated the function of Cdc42 in maintaining adherens junctions (AJs) and apical polarity in the Drosophila melanogaster neuroectodermal epithelium. About one third of cells exit the epithelium through ingression and become neuroblasts. Cdc42-compromised embryos lost AJs in the neuroectoderm during neuroblast ingression. In contrast, when neuroblast formation was suppressed, AJs were maintained despite the loss of Cdc42 function. Loss of Cdc42 function caused an increase in the endocytotic uptake of apical proteins, including apical polarity factors such as Crumbs, which are required for AJ stability. In addition, Cdc42 has a second function in regulating endocytotic trafficking, as it is required for the progression of apical cargo from the early to the late endosome. The Par complex acts as an effector for Cdc42 in controlling the endocytosis of apical proteins. This study reveals functional interactions between apical polarity proteins and endocytosis that are critical for stabilizing dynamic basolateral AJs.

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Localization of Cdc42 in epithelia of wild-type embryos and embryos expressing Cdc42-DN. (A and B) XZ reconstruction of image stacks of neuroectodermal cells of wild-type (A) and Cdc42-DN (B) embryos labeled for DEcad and Cdc42. (C) Schematic of an epithelial cell indicating the focal planes shown in panels D–I. (D–I) Apical membrane (D and G), AJ (E and H), and basolateral membrane (F and I) single-plane views of wild-type (D–F) and Cdc42-DN (G–I) embryos labeled for DEcad and Cdc42. (J and K) Wild-type (J) and Cdc42-DN (K) embryos labeled for Crb and Cdc42. Bars, 5 μm.
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fig3: Localization of Cdc42 in epithelia of wild-type embryos and embryos expressing Cdc42-DN. (A and B) XZ reconstruction of image stacks of neuroectodermal cells of wild-type (A) and Cdc42-DN (B) embryos labeled for DEcad and Cdc42. (C) Schematic of an epithelial cell indicating the focal planes shown in panels D–I. (D–I) Apical membrane (D and G), AJ (E and H), and basolateral membrane (F and I) single-plane views of wild-type (D–F) and Cdc42-DN (G–I) embryos labeled for DEcad and Cdc42. (J and K) Wild-type (J) and Cdc42-DN (K) embryos labeled for Crb and Cdc42. Bars, 5 μm.

Mentions: To address the question of the cellular mechanism used by Cdc42 to support apical polarity during Drosophila early neurogenesis, we first examined the distribution of Cdc42. To this end, we generated new Cdc42 antibodies and a transgenic line that expresses GFP-Cdc42 under Gal4/UAS control. Cdc42 antibodies and GFP-Cdc42, as detected with anti-GFP antibodies, showed identical distribution patterns (Fig. 3, A and D–F; and Fig. S1, available at http://www.jcb.org/cgi/content/full/jcb.200807020/DC1), with one exception (see following paragraph). Cdc42 is found in a punctate distribution throughout the cytoplasm of all ectodermal epithelial cells. Cdc42 appears enriched at the plasma membrane, in particular the AJs, where it is also found in small puncta rather than uniformly distributed as suggested by the examination of deconvolved confocal z stacks (see Materials and methods). Thus, Cdc42 colocalized with the apical membrane and the AJs but did not show any obvious apical enrichment.


Cdc42 and Par proteins stabilize dynamic adherens junctions in the Drosophila neuroectoderm through regulation of apical endocytosis.

Harris KP, Tepass U - J. Cell Biol. (2008)

Localization of Cdc42 in epithelia of wild-type embryos and embryos expressing Cdc42-DN. (A and B) XZ reconstruction of image stacks of neuroectodermal cells of wild-type (A) and Cdc42-DN (B) embryos labeled for DEcad and Cdc42. (C) Schematic of an epithelial cell indicating the focal planes shown in panels D–I. (D–I) Apical membrane (D and G), AJ (E and H), and basolateral membrane (F and I) single-plane views of wild-type (D–F) and Cdc42-DN (G–I) embryos labeled for DEcad and Cdc42. (J and K) Wild-type (J) and Cdc42-DN (K) embryos labeled for Crb and Cdc42. Bars, 5 μm.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
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getmorefigures.php?uid=PMC2600741&req=5

fig3: Localization of Cdc42 in epithelia of wild-type embryos and embryos expressing Cdc42-DN. (A and B) XZ reconstruction of image stacks of neuroectodermal cells of wild-type (A) and Cdc42-DN (B) embryos labeled for DEcad and Cdc42. (C) Schematic of an epithelial cell indicating the focal planes shown in panels D–I. (D–I) Apical membrane (D and G), AJ (E and H), and basolateral membrane (F and I) single-plane views of wild-type (D–F) and Cdc42-DN (G–I) embryos labeled for DEcad and Cdc42. (J and K) Wild-type (J) and Cdc42-DN (K) embryos labeled for Crb and Cdc42. Bars, 5 μm.
Mentions: To address the question of the cellular mechanism used by Cdc42 to support apical polarity during Drosophila early neurogenesis, we first examined the distribution of Cdc42. To this end, we generated new Cdc42 antibodies and a transgenic line that expresses GFP-Cdc42 under Gal4/UAS control. Cdc42 antibodies and GFP-Cdc42, as detected with anti-GFP antibodies, showed identical distribution patterns (Fig. 3, A and D–F; and Fig. S1, available at http://www.jcb.org/cgi/content/full/jcb.200807020/DC1), with one exception (see following paragraph). Cdc42 is found in a punctate distribution throughout the cytoplasm of all ectodermal epithelial cells. Cdc42 appears enriched at the plasma membrane, in particular the AJs, where it is also found in small puncta rather than uniformly distributed as suggested by the examination of deconvolved confocal z stacks (see Materials and methods). Thus, Cdc42 colocalized with the apical membrane and the AJs but did not show any obvious apical enrichment.

Bottom Line: Loss of Cdc42 function caused an increase in the endocytotic uptake of apical proteins, including apical polarity factors such as Crumbs, which are required for AJ stability.The Par complex acts as an effector for Cdc42 in controlling the endocytosis of apical proteins.This study reveals functional interactions between apical polarity proteins and endocytosis that are critical for stabilizing dynamic basolateral AJs.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario M5S 3G5, Canada.

ABSTRACT
Cell rearrangements require dynamic changes in cell-cell contacts to maintain tissue integrity. We investigated the function of Cdc42 in maintaining adherens junctions (AJs) and apical polarity in the Drosophila melanogaster neuroectodermal epithelium. About one third of cells exit the epithelium through ingression and become neuroblasts. Cdc42-compromised embryos lost AJs in the neuroectoderm during neuroblast ingression. In contrast, when neuroblast formation was suppressed, AJs were maintained despite the loss of Cdc42 function. Loss of Cdc42 function caused an increase in the endocytotic uptake of apical proteins, including apical polarity factors such as Crumbs, which are required for AJ stability. In addition, Cdc42 has a second function in regulating endocytotic trafficking, as it is required for the progression of apical cargo from the early to the late endosome. The Par complex acts as an effector for Cdc42 in controlling the endocytosis of apical proteins. This study reveals functional interactions between apical polarity proteins and endocytosis that are critical for stabilizing dynamic basolateral AJs.

Show MeSH
Related in: MedlinePlus