PLEKHG4B enables actin cytoskeletal remodeling during epithelial cell–cell junction formation

Abstract

Cell–cell junction formation requires actin cytoskeletal remodeling. Here, we show that PLEKHG4B, a Rho-guanine nucleotide exchange factor (Rho-GEF), plays a crucial role in epithelial cell–cell junction formation. Knockdown of PLEKHG4B decreased Cdc42 activity and tended to increase RhoA activity in A549 cells. A549 monolayer cells showed ‘closed junctions’ with closely packed actin bundles along the cell–cell contacts, but PLEKHG4B knockdown suppressed closed junction formation, and PLEKHG4B-knockdown cells exhibited ‘open junctions’ with split actin bundles located away from the cell–cell boundary. In Ca2+-switch assays, PLEKHG4B knockdown delayed the conversion of open junctions to closed junctions and β-catenin accumulation at cell–cell junctions. Furthermore, PLEKHG4B knockdown abrogated the reduction in myosin activity normally seen in the later stage of junction formation. The aberrant myosin activation and impairments in closed junction formation in PLEKHG4B-knockdown cells were reverted by ROCK inhibition or LARG/PDZ-RhoGEF knockdown. These results suggest that PLEKHG4B enables actin remodeling during epithelial cell–cell junction maturation, probably by reducing myosin activity in the later stage of junction formation, through suppressing LARG/PDZ-RhoGEF and RhoA–ROCK pathway activities. We also showed that annexin A2 participates in PLEKHG4B localization to cell–cell junctions.This article has an associated First Person interview with the first author of the paper.

DIRAS3 might function as a diagnostic biomarker and be related to immune infiltration in gliomas

“…In addition, among the 3381 DIRAS3-related differentially expressed genes screened in the TCGA database with |logFC | >1.5, corrected P-value < 0.01, SAA1, which had the highest positive correlation with DIRAS3, is a sensitive acute-phase high-density lipoprotein mainly produced by the liver as a response to acute in ammation and tissue injury in humans, assessing the acute-phase human in ammatory response process, and SAA1 may be involved in the body's immune system to promote the repair of damaged tissues, as well as being used as a diagnostic or prognostic marker for many diseases [30] , which is consistent with our results. The search for DIRAS3-binding proteins by STRING and the aforementioned intersection cross-tabulation analysis yielded three common members:MET, PLEKHG4B and MAP3K19.The MET receptor binds to its ligand, HGF, and induces MET dimerisation, tyrosine residue autophosphorylation, substrate docking, and activation of downstream signalling pathways [31] .The aberrant MET/HGF axis pathway is involved in the proliferation, survival, invasion and metastasis of tumour cells [31] .PLEKHG4B, a Rho-Guanine Nucleotide Exchange Factor (Rho-GEF), is localised to cell junctions and is involved in cell-cell junction maturation by decreasing myosin activity at the late stages of cell-cell junction formation [32] .The role of MAP3K19 is now less well studied, and has been reported to be associated with cancer progression associated with cancer progression [33] . Therefore, DIRAS3 may be involved in the regulation of SAA1, MET, PLEKHG4B and MAP3K19 to alter the tumour immune microenvironment and thereby promote glioma progression(Figure1E).…”

Interaction between Solo and PDZ-RhoGEF is involved in actin cytoskeletal remodeling and response to substrate stiffness

“…Additionally, BPGAP, a GAP of RhoA, binds to Vav1 in lamellipodia, inactivates RhoA, and facilitates the GEF activity of Vav1 toward Rac, resulting in the promotion of lamellipodia formation (Wong et al ., 2023). Moreover, PLEKHG4B, which has a structure similar with Solo, binds to PDZ-RhoGEF and LARG and inhibits the activation of their GEF activities downstream of the G-protein coupled receptor (Muller et al ., 2020; Ninomiya et al ., 2021). Conclusively, these findings suggest that the activity of Rho GTPases is diversely regulated by interactions with upstream regulators.…”

Identification of Arhgef12 and Prkci as genetic modifiers of retinal dysplasia in the Crb1rd8 mouse model

“…ARHGEF12 colocalizes and physically interacts with WTIP, an adaptor protein required for stabilizing cell-cell adhesions as they form in mouse renal podocytes [ 81 ]. In cultured human cells, ARHGEF12 mediates RHOA-CDC42 cross-talk in a complex with two other Dbl proteins, ARHGEF11 and PLEKHG4B [ 79 ], which directs actin remodeling at cell-cell junctions as they mature [ 82 ]. Interestingly, ARHGEF12 guanine nucleotide exchange activity requires interaction with the activated α subunits of heterotrimeric G proteins, G α12 , G α13 , and G αq [ 77 , 78 , 83 – 85 ] and are therefore regulated by the stimulation of G protein coupled receptors (GPCRs) that activate these subunits [ 85 – 87 ].…”