A Trio-RhoA-Shroom3 pathway is required for apical constriction and epithelial invagination

Abstract

SUMMARYEpithelial invagination is a common feature of embryogenesis. An example of invagination morphogenesis occurs during development of the early eye when the lens placode forms the lens pit. This morphogenesis is accompanied by a columnar-toconical cell shape change (apical constriction or AC) and is known to be dependent on the cytoskeletal protein Shroom3. Because Shroom3-induced AC can be Rock1/2 dependent, we hypothesized that during lens invagination, RhoA, Rock and a RhoA guanine nucleotide exchange factor (RhoA-GEF) would also be required. In this study, we show that Rock activity is required for lens pit invagination and that RhoA activity is required for Shroom3-induced AC. We demonstrate that RhoA, when activated and targeted apically, is sufficient to induce AC and that RhoA plays a key role in Shroom3 apical localization. Furthermore, we identify Trio as a RhoA-GEF required for Shroom3-dependent AC in MDCK cells and in the lens pit. Collectively, these data indicate that a Trio-RhoA-Shroom3 pathway is required for AC during lens pit invagination.

Apical constriction: themes and variations on a cellular mechanism driving morphogenesis

“…In addition, RhoA can activate Diaphanous (Dia)-related formins, which nucleate and facilitate the assembly of unbranched actin filaments (Goode and Eck, 2007). Apical constriction in several vertebrate and invertebrate systems requires RhoA GTPase activation (Barrett et al, 1997;Hacker and Perrimon, 1998;Plageman et al, 2011;Nishimura et al, 2012). In Drosophila gastrulation, RhoA (Rho1 in Drosophila) activation plays a central role in a signaling pathway that links tissue patterning and cell fate to apical constriction and cell invagination (Leptin, 2005).…”

“…Because Shroom3 is important for neural tube formation (Hildebrand and Soriano, 1999;Haigo et al, 2003;Nishimura and Takeichi, 2008), the question remains of how RhoA and Shroom3 cooperate to control ROCK localization and/or activity. RhoA and Shroom3 bind distinct regions of ROCK, presenting the possibility that ROCK can integrate these two signals to spatially control contractility (Nishimura and Takeichi, 2008;Plageman et al, 2011). In the eye lens placode, RhoA is necessary for Shroom3 localization and basolateral RhoA activation can ectopically recruit Shroom3 (Plageman et al, 2011).…”

“…RhoA and Shroom3 bind distinct regions of ROCK, presenting the possibility that ROCK can integrate these two signals to spatially control contractility (Nishimura and Takeichi, 2008;Plageman et al, 2011). In the eye lens placode, RhoA is necessary for Shroom3 localization and basolateral RhoA activation can ectopically recruit Shroom3 (Plageman et al, 2011). However, dominant-negative RhoA does not block Shroom3-mediated apical constriction in other cell types (Haigo et al, 2003;Hildebrand, 2005), suggesting that Shroom3 can mediate Rho-independent ROCK activation in other contexts.…”

Recent advances of animal model of focal segmental glomerulosclerosis

“…Myosin 1e (Myo1e) is one of the two Src homology 3 domain-containing "long-tailed" type I myosins in Actin filament cross-linking protein/Interacts with integrins and strengthens the podocyte-GBM interaction Atypical protein kinase C [68][69][70][71] Tight junctions/Formation of Par complex and interacts with slit diaphragm Rhophilin-1 [80] Rho GTPase activating protein 24 [80] Cytoplasm/Rho GTPase-interacting protein, integrity of glomerular filtration barrier Angiotensin II receptor [55][56][57] Angiotensin-converting enzyme [55][56][57] Membrane/pseudocyst formation at podocyte CD2-associated protein [65][66][67] CD2-associated protein [64] Insertion site of the slit diaphragm/Formation SD complex with podocin and nephrin Laminin subunit beta-2 [81][82][83][84] Laminin subunit beta-2 [81][82][83][84] Podocyte anchoring and differentiation in GBM microRNA 193α [74,75] Cytoplasm/Inhibition of expression of WT-1 Myosin 1e [49,50] Myosin 1e [49,50] Actin binding long-tailed motor protein/Regulation of actin cytoskeleton Nuclear factor of activated T cells [76,77] Transient receptor potential 6 [53,54] Membrane/the activation of calcineurin-NFAT/Wnt signaling via the increased calcium influx Podocin [46] Podocin [58,59] Insertion site of the SD/SD assembly and maintaining the signaling of nephrin Shroom family member 3 …”

“…Shroom3 interacts and recruits Rho-kinase (Rock), resulting in the phosphorylation and activation of nonmuscle myosin II (MyoII). Activation of this Rock/MyoII signaling pathway causes localized contraction of actin-myosin networks at the apical surface of the podocyte, resulting in changes in cell morphology [51]. In addition, Shroom3 heterozygous (Shroom3Gt/+) mice showed developmental abnormalities that manifested as adult-onset glomerulosclerosis and proteinuria [52] (Table 2; Fig.…”