RhoB affects macrophage adhesion, integrin expression and migration

Ludwig Institute for Cancer Research, Royal Free and University College School of Medicine, London, UK.
Experimental Cell Research (Impact Factor: 3.37). 11/2007; 313(16):3505-16. DOI: 10.1016/j.yexcr.2007.07.014
Source: PubMed

ABSTRACT Rho GTPases regulate multiple cellular responses, including cell motility and cell cycle progression. The Rho isoform RhoB represses transformation and affects endosomal trafficking, but its effects on cell adhesion and migration have not been investigated in detail. Here we show that RhoB-null macrophages are more rounded than wild-type macrophages on fibronectin and uncoated glass, and have reduced adhesion to ICAM-1 and glass but not fibronectin. This correlated with lower cell surface expression of beta2 and beta3 integrins but not beta1 integrin. RhoB-null cells migrated faster than Wt cells on fibronectin, consistent with their smaller spread area, but slower than Wt cells on glass, reflecting their reduced adhesion. C3 transferase, which inhibits RhoA, RhoB and RhoC, induced cell spreading but this effect was reduced in RhoB-null cells. However, RhoB is not required for assembly of podosomes, which are integrin-based adhesion sites, whereas C3 transferase induced a decrease in podosomes and defects in tail retraction. Since macrophages do not express RhoC, these effects of C3 transferase are due to inhibition of RhoA rather than RhoB. Our results suggest that RhoB affects cell shape and migration by regulating surface integrin levels.

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    • "macrophages, RhoB has been postulated to affect adhesion by affecting surface levels of b-integrins (Wheeler and Ridley, 2007). We demonstrate that RhoB mediates ATF-induced upregulation of surface integrin levels, explaining how RhoB specifically affects uPAR responses, and hence uPAR-dependent signalling. "
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    ABSTRACT: Urokinase-type plasminogen activator (uPA) and its receptor, uPAR, play important roles in promoting cancer cell adhesion, migration and invasion. Rho GTPases are key coordinators of these processes; the Rho GTPase Rac1 has previously been implicated in uPA- and/or uPAR-induced migratory or morphological cell responses. We used RNAi to deplete 12 different Rho GTPases to screen for effects on uPA-stimulated migration, and found that depletion of RhoB significantly reduces uPA-induced migration and invasion of prostate carcinoma cells. RhoB depletion did not affect the expression or surface levels of uPAR but reduced the uPAR-induced increase in levels of several integrins and inhibited uPAR signalling to the actin regulator cofilin, the cell-adhesion signal-transduction adaptor molecule paxillin and the serine/threonine kinase Akt. uPAR rapidly activated RhoB and increased RhoB expression. RhoB depletion also reduced cell adhesion to and spreading on vitronectin, which is a uPAR ligand. This correlated with decreased association between integrins and uPAR and reduced integrin β1 activity. Our results indicate that RhoB is a key regulator of uPAR signalling in cell adhesion, migration and invasion.
    Journal of Cell Science 02/2012; 125(Pt 10):2369-80. DOI:10.1242/jcs.091579 · 5.33 Impact Factor
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    • "The work of several laboratories has identified important roles for RhoB in the endocytic trafficking of RTKs, such as EGFR and PDGFR, along with key downstream signaling molecules Src, Akt and ERK [Adini et al., 2003; Huang et al., 2007; Sandilands et al., 2004; Wherlock et al., 2004]. A study on macrophages has reported that RhoB affects cell adhesion and migration on different substrates in response to colony stimulating factor-1 (CSF-1) stimulation by regulating cell surface expression of integrins [Wheeler and Ridley, 2007]. However, the role of RhoB in growth factor induced cell migration has not been studied in detail. "
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    ABSTRACT: The small GTPase RhoB regulates endocytic trafficking of receptor tyrosine kinases (RTKs) and the non-receptor kinases Src and Akt. While receptor-mediated endocytosis is critical for signaling processes driving cell migration, mechanisms that coordinate endocytosis with the propagation of migratory signals remain relatively poorly understood. In this study, we show that RhoB is essential for activation and trafficking of the key migratory effectors Cdc42 and Rac in mediating the ability of platelet-derived growth factor (PDGF) to stimulate cell movement. Stimulation of the PDGF receptor-β on primary vascular smooth muscle cells (VSMCs) results in RhoB-dependent trafficking of endosome-bound Cdc42 from the perinuclear region to the cell periphery, where the RhoGEF Vav2 and Rac are also recruited to drive formation of circular dorsal and peripheral ruffles necessary for cell migration. Our findings identify a novel RhoB-dependent endosomal trafficking pathway that integrates RTK endocytosis with Cdc42/Rac localization and cell movement.
    Journal of Cellular Biochemistry 06/2011; 112(6):1572-84. DOI:10.1002/jcb.23069 · 3.37 Impact Factor
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    • "In macrophages, Rho B inactivation results in decreased surface expression of integrins ␤2 and ␤3, whereas ␤1 surface expression remains constant. However, modification of this integrin pattern does not affect podosome formation (Wheeler and Ridley, 2007). In contrast, the importance of ␤1 in invadopodia was suggested by activation of these integrins by soluble antibody, which leads to an increase in ECM degradation (Nakahara et al., 1998). "
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    ABSTRACT: Invadosomes are adhesion structures involved in tissue invasion that are characterized by an intense actin polymerization-depolymerization associated with β1 and β3 integrins and coupled to extracellular matrix (ECM) degradation activity. We induced the formation of invadosomes by expressing the constitutive active form of Src, SrcYF, in different cell types. Use of ECM surfaces micropatterned at the subcellular scale clearly showed that in mesenchymal cells, integrin signaling controls invadosome activity. Using β1⁻/⁻ or β3⁻/⁻ cells, it seemed that β1A but not β3 integrins are essential for initiation of invadosome formation. Protein kinase C activity was shown to regulate autoassembly of invadosomes into a ring-like metastructure (rosette), probably by phosphorylation of Ser785 on the β1A tail. Moreover, our study clearly showed that β1A links actin dynamics and ECM degradation in invadosomes. Finally, a new strategy based on fusion of the photosensitizer KillerRed to the β1A cytoplasmic domain allowed specific and immediate loss of function of β1A, resulting in disorganization and disassembly of invadosomes and formation of focal adhesions.
    Molecular biology of the cell 10/2010; 21(23):4108-19. DOI:10.1091/mbc.E10-07-0580 · 5.98 Impact Factor
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