Interplay between cortical actin and E-cadherin dynamics regulates cell shape in theDrosophilaembryonic epidermis

Abstract

11Precise regulation of cell shape is vital for building functional tissues. Here, we study the 12 mechanisms which lead to the formation of highly elongated anisotropic epithelial cells in the 13Drosophila epidermis. We demonstrate that this cell shape is the result of two counteracting 14 mechanisms at the cell surface: actomyosin, which inhibits cell elongation downstream of 15RhoA signalling, and intercellular adhesion, modulated via clathrin-mediated endocytosis of 16 E-cadherin, which promotes cell elongation downstream of the GTPase Arf1. We show that 17 these two mechanisms are interconnected, with RhoA signalling activity reducing Arf1 18 recruitment to the plasma membrane. Additionally, cell adhesion itself regulates both 19 mechanisms: p120-catenin, a regulator of intercellular adhesion, promotes the activity of both 20Arf1 and RhoA. Altogether, we uncover a complex network of interactions between cell-cell 21 adhesion, the endocytic machinery, and the actomyosin cortex, and demonstrate how this 22

Arf6 determines tissue architecture by stabilizing intercellular adhesion

“…2A-B). In control cells at this stage of embryonic development, MyoII-YFP was enriched at the AP cell borders, consistent with previous observations [7,12,38]. Expression of Arf6 DN led to a significant increase in the levels of MyoII-YFP at both cell borders (p=0.0001, p=0.04, Fig.…”

“…Our recent studies have demonstrated key roles for membrane trafficking in the regulation of cell shape and specifically in the elongation of cells in the embryonic epidermis [7]. Arf6 regulates vesicle trafficking between the PM and endosomal system [22,46,47].…”

“…As we have previously found that both the levels of E-cad and its dynamics contribute to cell shape [7], we decided to explore the effect of the Arf6 DN on the dynamics of E-cad at the cell surface using FRAP. In our previous work we showed E-cad-GFP recovered to 70% and 50% of pre-bleach signal for the DV and AP cell borders respectively [12,37].…”

“…A key regulator of Ecad stability at the cell surface is the molecule p120-catenin (p120ctn) [7,37,50,51]. The overexpression of p120ctn stabilizes E-cad within junctions in both mammalian and Drosophila cells [7,49,52]. If Arf6 were stabilizing E-cad downstream of p120ctn, one might expect its increased localisation to the PM upon p120ctn overexpression.…”

The walkoff effect: cargo distribution implies motor type in bidirectional microtubule bundles

“…To test the second prediction that the uniform cargo distribution might be more favoured by kinesin activity rather than dynein, we selected the Golgi apparatus, whose distribution is dependant on MTs [75][76][77]. We used the GFP-tagged Arf1 protein to visualized the Golgi apparatus [78]. In epidermal cells, Golgi appears as multiple spots of Arf1 in the plane of cell-cell adhesion and MTs (Fig.…”