Positive feedback between Dia1, LARG, and RhoA regulates cell morphology and invasion

Abstract

The RhoA-effector Dia1 controls actin-dependent processes such as cytokinesis, SRF transcriptional activity, and cell motility. Dia1 polymerizes actin through its formin homology (FH) 2 domain. Here we show that Dia1 acts upstream of RhoA independently of its effects on actin assembly. Dia1 binds to the leukemia-associated Rho-GEF (LARG) through RhoA-dependent release of Dia1 autoinhibition. The FH2 domain stimulates the guanine nucleotide exchange activity of LARG in vitro. Our results reveal that Dia1 is necessary for LPA-stimulated Rho/ROCK signaling and bleb-associated cancer cell invasion. Thus, Dia1-dependent RhoA activation constitutes a positive feedback mechanism to modulate cell behavior.Supplemental material is available at http://www.genesdev.org.Received January 11, 2007; revised version accepted May 8, 2007. Diaphanous-related formins (DRFs) are Rho-GTPasebinding proteins that possess conserved functions in actin cytoskeleton dynamics exerted through their formin homology (FH) 2 domains (Goode and Eck 2007). DRFs are involved in essential cellular processes such as cytokinesis, cell movement, and polarity (Faix and Grosse 2006;Gomez et al. 2007), which are frequently deregulated during pathological situations like tumor cell transformation and metastasis (Sahai 2005). The dormant conformation of the DRF Dia1 is maintained by intramolecular association of its regulatory N terminus to the diaphanous autoregulatory domain (DAD), which is relieved through binding of active RhoA (Lammers et al. 2005;Otomo et al. 2005a). The catalytic FH2 domain is believed to become "exposed" by conformational changes in the DRFs to promote barbed end actin polymerization by forming a tethered dimer (Xu et al. 2004;Otomo et al. 2005a). The FH2 domain of Dia1 promotes stress fiber formation and transcriptional activation of the MAL/SRF pathway through its actin-polymerizing activity (Copeland and Treisman 2002;Grosse et al. 2003;Miralles et al. 2003). A Dia1 mutant defective in FH2 dimerization interferes with lysophosphatidic acid (LPA)-induced stress fiber formation and SRF activity (Copeland and Treisman 2002), suggesting that Dia1 is part of LPA signal transduction known to play an important role in cell proliferation and metastasis of a variety of human cancers (Mills and Moolenaar 2003). LPA receptors belong to the group of G-protein-coupled receptors that activate the heterotrimeric G-proteins G 12 and G 13 , which can bind to RGS-containing Rho-GEFs such as leukemia-associated Rho-GEF (LARG), initially isolated from a patient with acute myeloid leukemia (AML) (Kourlas et al. 2000;Vazquez-Prado et al. 2004). Rhodependent mechanisms have emerged as critical processes in tumor progression (Sahai and Marshall 2002;Lozano et al. 2003), and evidence exists that Rho/ROCK function is essential to promote a specific type of rounded bleb-associated mode of cell invasion (Sahai and Marshall 2003;Wyckoff et al. 2006). However, the role of DRFs in tumor cell behavior has not been investigated.In this study, we provide evi...

Coronin 1B supports RhoA signaling at cell-cell junctions through Myosin II

“…[31][32][33][34][35][36] While the role for active RhoA signaling in facilitating essential cellular processes has been wellestablished 9,[37][38][39][40][41] there are circumstances where RhoA signaling must be downregulated, either physiologically or pathologically to elicit a biological response. 41,42 Given the importance of the actomyosin cytoskeleton in positively regulating RhoA signaling, 7,[43][44][45] targeting actin-regulators such as Coronin 1B might be one of the approaches to achieve a precise spatiotemporal regulation of RhoA. In summary, our analysis contributes to the growing notion that Rho-GTPases and cytoskeleton regulators act in sync to establish epithelial homeostasis and contractility.…”

Connectivity mapping identifies HDAC inhibitors for the treatment of t(4;11)-positive infant acute lymphoblastic leukemia

“…Supporting this assumption, these genes frequently involve potential proto-oncogenes, like MYC, 33 HOXA9, 34 SET, 35 RUNX1, 36 RAN, 37 PARK7, 38,39 and DIAPH1. 40 Moreover, several of the hypomethylated genes that we identified in this study, that is, ZCCHC7, HOXA9 and MYC, have all been shown to be activated by the MLL-AF4 fusion itself via H3K79 methylation through the recruitment of DOT1L. 13,14 This observation indisputably illustrates interactions between DNA methylation and histone modifica- …”

Differing and isoform-specific roles for the formin DIAPH3 in plasma membrane blebbing and filopodia formation

“…Only few studies previously addressed the involvement of specific actin nucleators in PM blebbing. Using experimental systems in which PM blebbing was induced by genetic manipulation or protein overexpression, nucleators such as mDia1, mDia2, FHOD1, Arp2/3 that are also involved in the regulation of diverse additional cellular actin remodeling events were implicated in blebbing [12,[41][42][43]. In this present study, we conducted a comprehensive analysis of the involvement of endogenously expressed human actin nucleators in PM blebbing of adhering HeLa cells.…”

“…Conceivably, the set of nucleators involved may differ between cell types and bleb stimuli. Identified already as a prerequisite for PM blebbing during amoeboid invasion of cancer cells [41], Dia1 may represent a nucleator with roles in a broad range of PM blebbing scenarios. Interestingly, with Spir1 and FMN1, we also identified two nucleators that cooperate in regulated actin remodeling [44,45], and addressing their specific role in PM blebbing will be an interesting goal for future studies.…”