Role of RHOB in the antiproliferative effect of glucocorticoid receptor on macrophage RAW264.7 cells

Abstract

Although glucocorticoid (GC) has been reported to inhibit macrophage killing activity and cytokine production in response to proinflammatory stimuli, the effect of GC on macrophage proliferation is controversial. In our previous study, we found that inhibition of glucocorticoid receptor (GR) expression in murine macrophage cell line RAW264.7 cells (RAW-GR(K) cells) by RNAi significantly promoted cell proliferation. In the present study, we provide the evidence that the expression of Rhob, a member of Rho GTPases with anti-cancer character, remarkably decreased in RAW-GR(K) and RAW264.7 cells transiently transfected with GR-RNAi vector. Overexpression or constitutive activation of Rhob in RAW-GR(K) and RAW264.7 cells by transfection with wild-type Rhob expression vector (Rhob-wt) or constitutively activated Rhob plasmid (Rhob-V14) resulted in decreased proliferation of the two cell lines. Oppositely, the proliferation of RAW264.7 cells was significantly increased when the expression of Rhob by RNA interference technique or the activity of Rhob by transfection with dominant negative Rhob mutant that is defective in nucleotide binding (Rhob-N19) was inhibited. In addition, enhanced activity of Akt, but not MAPK3/1 or MAPK14, was found in RAW-GR(K) cells. Blocking the pathway of phosphatidylinositol 3-kinase (PI3K)/Akt with the specific inhibitor LY294002 decreased the proliferation and elevated RHOB protein level, indicating that PI3K/Akt signal plays its role of proliferation modulation upstream of RHOB protein. In conclusion, these results demonstrate that Rhob plays an important role in the antiproliferative effect of GR on RAW264.7 cells by GR/Akt/Rhob signaling and Rhob negatively regulates the proliferation of RAW264.7 cells.

Induction of small G protein RhoB by non‐genotoxic stress inhibits apoptosis and activates NF‐κB

“…Although RhoA and RhoB share 86% amino acid sequence identity, RhoB displays several distinct properties including subcellular localization in endosomes and pre‐lysosomal compartment, rapid turnover at mRNA and protein level, and post‐translational modification by either farnesylation (RhoB‐F) or geranylgeranylation (RhoB‐GG) (Baron et al, 2000; Michaelson et al, 2001; Wang et al, 2003; Mazieres et al, 2007). Furthermore, RhoB, unlike RhoA and RhoC that have positive role in proliferation and malignant transformation processes, has been demonstrated to inhibit cell proliferation and tumor growth in a nude mouse xenograft model by our group (Chen et al, 2006; Wang et al, 2009) and others (Prendergast, 2001; Mazieres et al, 2004; Jiang et al, 2004a; Huang and Prendergast, 2006). Additionally, in contrast to RhoA which is constitutively expressed, RhoB has been shown to be induced by some growth factors such as EGF, PDGF (Jahner and Hunter, 1991), TGFβ (Engel et al, 1998), and more importantly, by some genotoxic stressor, such as UV and chemotherapeutic drugs (e.g., cisplatin and 5‐FU) (Fritz et al, 1995; Fritz and Kaina, 1997, 2000; Liu et al, 2001; Delmas et al, 2002; Jiang et al, 2004a,b; Canguilhem et al, 2005).…”

Distinct biological activities of C3 and ADP‐ribosyltransferase‐deficient C3‐E174Q

“…RhoB has been implicated in the regulation of cell proliferation, as ectopic expression of constitutively active RhoB inhibits proliferation [31]. Next, the effects of C3 and C3-E174Q on HT22 proliferation was analysed over a 7-day period ( Fig.…”

Poly(lactide-co-glycolide) nanoparticle assembly for highly efficient delivery of potent therapeutic agents from medical devices

“…One mechanism of DEX induced macrophage cell number reduction is associated with the glucocorticoid receptor binding and the subsequent suppression of macrophage cell growth [22-24]. Therefore, when the macrophage cells were exposed to high dosage of DEX, it is possible that the glucocorticoid receptors on the cell surface were saturated and thus limited the cell responses [53, 54], despite the large quantity of the drug available in the cell culture.…”

“…DEX has been demonstrated to alter the healing responses after device implantation, by decreasing the number of infiltrating macrophage cells associated with inflammation [20, 21]. One mechanism of DEX induced macrophage cell number reduction is associated with the glucocorticoid receptor binding and the subsequent suppression of macrophage cell growth [22-24]. Administration of plasmid DNA, in contrast, can lead to production of proteins needed to enhance cell survival or cell function around the implant site.…”