Binding of GEF-H1 to the Tight Junction-Associated Adaptor Cingulin Results in Inhibition of Rho Signaling and G1/S Phase Transition

Division of Cell Biology, Institute of Ophthalmology, University College London, UK.
Developmental Cell (Impact Factor: 9.71). 06/2005; 8(5):777-86. DOI: 10.1016/j.devcel.2005.03.003
Source: PubMed


The activity of Rho GTPases is carefully timed to control epithelial proliferation and differentiation. RhoA is downregulated when epithelial cells reach confluence, resulting in inhibition of signaling pathways that stimulate proliferation. Here we show that GEF-H1/Lfc, a guanine nucleotide exchange factor for RhoA, directly interacts with cingulin, a junctional adaptor. Cingulin binding inhibits RhoA activation and signaling, suggesting that the increase in cingulin expression in confluent cells causes downregulation of RhoA by inhibiting GEF-H1/Lfc. In agreement, RNA interference of GEF-H1 or transfection of GEF-H1 binding cingulin mutants inhibit G1/S phase transition of MDCK cells, and depletion of cingulin by regulated RNA interference results in irregular monolayers and RhoA activation. These results indicate that forming epithelial tight junctions contribute to the downregulation of RhoA in epithelia by inactivating GEF-H1 in a cingulin-dependent manner, providing a molecular mechanism whereby tight junction formation is linked to inhibition of RhoA signaling.

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    • "Nevertheless, GEF-H1 regulates paracellular permeability in both epithelial and endothelial cells, and is required for junction dissociation in response to Ca 2+ depletion, a process that is influenced by its effect on cell shape and dynamics (Benais-Pont et al., 2003; Birukova et al., 2006; Samarin et al., 2007). GEF-H1 also promotes cell cycle progression by regulating gene expression (Aijaz et al., 2005; Nie et al., 2009). This involves the activation of the ZO-1- associated nucleic-acid-binding protein (ZONAB, the canine homologue of human YBX3, also known as DBPA), a regulator of transcription of cell cycle genes (e.g. "
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    • "Tight junctions are specifically relevant for water and small protein containment within the vessel lumens. Although cingulin is known to regulate tight junction redistribution via GEF-H1 (Aijaz et al., 2005), we have not yet identified our direct target structure of our peptide Xib13. We show that the non-perfused area on day 12 is smaller in Xib13- treated animals. "
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    • "On the other hand, in cingulin KD cells, EB1 signals tended to be located end on with respect to the membranes at points of cell–cell adhesion (Videos 4 and 5). Cingulin is also reported to associate with actin filaments (D'Atri and Citi, 2001) as well as with guanine nucleotide exchange factor (GEF)–H1 and p114 RhoGEF, as shown in MDCK and Caco-2 cells, respectively (Aijaz et al., 2005; Terry et al., 2011). There was no difference in actin filament arrangement, myosin light chain phosphorylation, p114 RhoGEF, or GEF-H1 between wild-type Eph4 and cingulin KD Eph4 cells (Fig. S2, B–E). "
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