Crb Apical Polarity Proteins Maintain Zebrafish Retinal Cone Mosaics via Intercellular Binding of Their Extracellular Domains

BackgroundPodocyte slit diaphragms (SDs) are intercellular junctions that function as size-selective filters, excluding most proteins from urine. Abnormalities in SDs cause proteinuria and nephrotic syndrome. Podocytes exhibit apicobasal polarity, which can affect fundamental aspects of cell biology, including morphology, intercellular junction formation, and asymmetric protein distribution along the plasma membrane. Apical polarity protein mutations cause nephrotic syndrome, and data suggest apical polarity proteins regulate SD formation. However, there is no evidence that basolateral polarity proteins regulate SDs. Thus, the role of apicobasal polarity in podocytes remains unclear.MethodsGenetic manipulations and transgenic reporters determined the effects of disrupting apicobasal polarity proteins in Drosophila nephrocytes, which have SDs similar to those of mammalian podocytes. Confocal and electron microscopy were used to characterize SD integrity after loss of basolateral polarity proteins, and genetic-interaction studies illuminated relationships among apicobasal polarity proteins.ResultsThe study identified four novel regulators of nephrocyte SDs: Dlg, Lgl, Scrib, and Par-1. These proteins comprise the basolateral polarity module and its effector kinase. The data suggest these proteins work together, with apical polarity proteins, to regulate SDs by promoting normal endocytosis and trafficking of SD proteins.ConclusionsGiven the recognized importance of apical polarity proteins and SD protein trafficking in podocytopathies, the findings connecting basolateral polarity proteins to these processes significantly advance our understanding of SD regulation.

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Apical polarity proteins recruit the RhoGEF Cysts to promote junctional myosin assembly

The Journal of Cell Biology ◽

10.1083/jcb.201807106 ◽

2019 ◽

Vol 218 (10) ◽

pp. 3397-3414 ◽

Cited By ~ 6

Author(s):

Jordan T. Silver ◽

Frederik Wirtz-Peitz ◽

Sérgio Simões ◽

Milena Pellikka ◽

Dong Yan ◽

...

Keyword(s):

Rho Gtpases ◽

Rho Gtpase ◽

Adherens Junctions ◽

Nucleotide Exchange ◽

Temporal Regulation ◽

Apical Polarity ◽

Polarity Proteins ◽

Spatio Temporal ◽

Crumbs Complex

The spatio-temporal regulation of small Rho GTPases is crucial for the dynamic stability of epithelial tissues. However, how RhoGTPase activity is controlled during development remains largely unknown. To explore the regulation of Rho GTPases in vivo, we analyzed the Rho GTPase guanine nucleotide exchange factor (RhoGEF) Cysts, the Drosophila orthologue of mammalian p114RhoGEF, GEF-H1, p190RhoGEF, and AKAP-13. Loss of Cysts causes a phenotype that closely resembles the mutant phenotype of the apical polarity regulator Crumbs. This phenotype can be suppressed by the loss of basolateral polarity proteins, suggesting that Cysts is an integral component of the apical polarity protein network. We demonstrate that Cysts is recruited to the apico-lateral membrane through interactions with the Crumbs complex and Bazooka/Par3. Cysts activates Rho1 at adherens junctions and stabilizes junctional myosin. Junctional myosin depletion is similar in Cysts- and Crumbs-compromised embryos. Together, our findings indicate that Cysts is a downstream effector of the Crumbs complex and links apical polarity proteins to Rho1 and myosin activation at adherens junctions, supporting junctional integrity and epithelial polarity.

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A Rich1/Amot Complex Regulates the Cdc42 GTPase and Apical-Polarity Proteins in Epithelial Cells

Cell ◽

10.1016/j.cell.2006.02.045 ◽

2006 ◽

Vol 125 (3) ◽

pp. 535-548 ◽

Cited By ~ 247

Author(s):

Clark D. Wells ◽

James P. Fawcett ◽

Andreas Traweger ◽

Yojiro Yamanaka ◽

Marilyn Goudreault ◽

...

Keyword(s):

Epithelial Cells ◽

Apical Polarity ◽

Polarity Proteins

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The RhoGEF Cysts couples apical polarity proteins to Rho and myosin activity at adherens junctions

10.1101/617134 ◽

2019 ◽

Author(s):

Jordan T. Silver ◽

Frederik Wirtz-Peitz ◽

Sérgio Simões ◽

Milena Pellikka ◽

Dong Yan ◽

...

Keyword(s):

Rho Gtpases ◽

Rho Gtpase ◽

Adherens Junctions ◽

Coiled Coil ◽

Terminal Region ◽

Nucleotide Exchange ◽

Apical Polarity ◽

Polarity Proteins ◽

Spatio Temporal

AbstractThe spatio-temporal regulation of small Rho GTPases is crucial for the dynamic stability of epithelial tissues. However, how RhoGTPase activity is controlled during development remains largely unknown. To explore the regulation of Rho GTPases in vivo we analyzed the Rho GTPase guanine nucleotide exchange factor (RhoGEF) Cysts, the Drosophila orthologue of mammalian p114RhoGEF, GEF-H1, p190RhoGEF, and AKAP-13. Loss of Cysts causes a phenotype that closely resemble the mutant phenotype of the apical polarity regulator Crumbs. This phenotype can be suppressed by the loss of basolateral polarity proteins suggesting that Cysts in an integral component of the apical polarity protein network. Cysts activates Rho at adherens junctions to promote junctional enrichment of myosin II, which requires the RhoGEF domain and the coiled-coil domain containing C-terminal region of Cysts. Cysts recruitment to the apico-lateral cortex depends on Crumbs and Bazooka/Par3 and requires multiple domains within Cysts including the C-terminal region. Together, our findings indicate that Cysts links apical polarity proteins to Rho1 and myosin activation at adherens junctions to support junctional and epithelial integrity in the Drosophila ectoderm.

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A contractile actomyosin network linked to adherens junctions by Canoe/afadin helps drive convergent extension

Molecular Biology of the Cell ◽

10.1091/mbc.e11-05-0411 ◽

2011 ◽

Vol 22 (14) ◽

pp. 2491-2508 ◽

Cited By ~ 105

Author(s):

Jessica K. Sawyer ◽

Wangsun Choi ◽

Kuo-Chen Jung ◽

Li He ◽

Nathan J. Harris ◽

...

Keyword(s):

Cell Shape ◽

Shape Change ◽

Adherens Junction ◽

Tissue Level ◽

The Body ◽

Convergent Extension ◽

Planar Polarity ◽

Cell Shape Change ◽

Apical Polarity ◽

Polarity Proteins

Integrating individual cell movements to create tissue-level shape change is essential to building an animal. We explored mechanisms of adherens junction (AJ):cytoskeleton linkage and roles of the linkage regulator Canoe/afadin during Drosophila germband extension (GBE), a convergent-extension process elongating the body axis. We found surprising parallels between GBE and a quite different morphogenetic movement, mesoderm apical constriction. Germband cells have an apical actomyosin network undergoing cyclical contractions. These coincide with a novel cell shape change—cell extension along the anterior–posterior (AP) axis. In Canoe's absence, GBE is disrupted. The apical actomyosin network detaches from AJs at AP cell borders, reducing coordination of actomyosin contractility and cell shape change. Normal GBE requires planar polarization of AJs and the cytoskeleton. Canoe loss subtly enhances AJ planar polarity and dramatically increases planar polarity of the apical polarity proteins Bazooka/Par3 and atypical protein kinase C. Changes in Bazooka localization parallel retraction of the actomyosin network. Globally reducing AJ function does not mimic Canoe loss, but many effects are replicated by global actin disruption. Strong dose-sensitive genetic interactions between canoe and bazooka are consistent with them affecting a common process. We propose a model in which an actomyosin network linked at AP AJs by Canoe and coupled to apical polarity proteins regulates convergent extension.

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