Response Gene To Complement 32 Expression Research Articles

RGC32 promotes the progression of ccRCC by activating the NF-κB/SHP2/EGFR signaling pathway.

The role and clinical significance of the response gene to complement 32 (RGC32) in various cancers have been documented, yet its implications in clear cell Renal Cell Carcinoma (ccRCC) remain underexplored. This study investigated RGC32's diagnostic and prognostic relevance in ccRCC using bioinformatics methods with data from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO). The impact of RGC32 on ccRCC progression was assessed through nude mouse tumor assays. Immunohistochemistry evaluated RGC32 levels in ccRCC and adjacent normal tissues, while cell proliferation, migration, and invasion capabilities were analyzed using CCK-8, monoclonal proliferation assays, Transwell, and wound healing assays, respectively. Western blotting measured relevant protein expressions. Bioinformatics analysis highlighted RGC32's significant role in ccRCC pathogenesis. Elevated RGC32 expression in ccRCC tissues was linked to disease progression. Functionally, RGC32 was found to enhance the expression of proteins such as p-PI3K, CyclinA1, CyclinD1, p-STAT3, MMP2, MMP3, MMP9, p-SMAD2/3, Snail, Slug, and N-Cadherin via the NF-κB/SHP2/EGFR pathway, while decreasing E-cadherin levels. Moreover, RGC32 facilitated ccRCC cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT). RGC32 is a pivotal factor in ccRCC development, primarily through the activation of the NF-κB/SHP2/EGFR signaling pathway.

Response gene to complement 32 expression in macrophages augments paracrine stimulation-mediated colon cancer progression

M2-polarized tumor associated macrophages (TAMs) play an important role in tumor progression. It has been reported that response gene to complement 32 (RGC-32) promotes M2 macrophage polarization. However, whether RGC-32 expression in macrophages could play a potential role in tumor progression remain unclear. Here we identified that increasing RGC-32 expression in colon cancer and tumor associated macrophages was positively correlated with cancer progression. In vitro studies confirmed that colon cancer cells upregulated RGC-32 expression of macrophages via secreting TGF-β1. RGC-32 expression promoted macrophage migration. In addition, stimulation of HCT-116 cells with the condition mediums of RGC-32-silienced or over-expressed macrophages affected tumor cell colony formation and migration via altered COX-2 expression. In an animal model, macrophages with RGC-32 knockdown significantly decreased the expression of COX-2 and Ki67 in the xenografts, and partly inhibited tumor growth. Together, our results provide the evidences for a critical role of TGF-β1/RGC-32 pathway in TAMs and colon cancer cells during tumor progression.

Loss of Response Gene to Complement 32 (RGC-32) in Diabetic Mouse Retina Is Involved in Retinopathy Development.

Diabetic retinopathy (DR) is a severe and recurrent microvascular complication in diabetes. The multifunctional response gene to complement 32 (RGC-32) is involved in the regulation of cell cycle, proliferation, and apoptosis. To investigate the role of RGC-32 in the development of DR, we used human retinal microvascular endothelial cells under high-glucose conditions and type 2 diabetes (T2D) mice (+Leprdb/ + Leprdb, db/db). The results showed that RGC-32 expression increased moderately in human retinal endothelial cells under hyperglycemic conditions. Histopathology and RGC-32 expression showed no significant changes between T2D and control mice retina at 16 and 24 weeks of age. However, RGC-32 expression was significantly decreased in T2D mouse retina compared to the control group at 32 weeks of age, which develop features of the early clinical stages of DR, namely reduced retinal thickness and increased ganglion cell death. Moreover, immunohistochemistry showed that RGC-32 was predominantly expressed in the photoreceptor inner segments of control mice, while the expression was dramatically lowered in the T2D retinas. Furthermore, we found that the level of anti-apoptotic protein Bcl-2 was decreased (approximately 2-fold) with a concomitant increase in cleaved caspase-3 (approximately 3-fold) in T2D retina compared to control. In summary, RGC-32 may lose its expression in T2D retina with features of DR, suggesting that it plays a critical role in DR pathogenesis.

Abstract 168: Response Gene to Complement 32 Suppresses Adipose Tissue Thermogenic Genes through Inhibiting Beta3 Adrenergic Receptor mTORC1 Signaling

Our previous study have shown that response gene to complement 32 (RGC-32) deficiency (Rgc32-/-) protects mice from diet-induced obesity and increases thermogenic gene expression in adipose tissues. However, the underlying mechanisms by which RGC-32 regulates thermogenic gene expression remain to be determined. In the present study, we found that RGC-32 expression in white adipose tissue (WAT) was suppressed during cold exposure-induced WAT browning. Rgc32-/- significantly increased thermogenic gene expression in the differentiated stromal vascular fraction (SVF) of inguinal WAT (iWAT). Interestingly, Rgc32-/- and cold exposure regulated a common set of genes in iWAT as shown by RNA sequencing data. Pathway enrichment analyses showed that RGC-32 deficiency downregulated PI3K/Akt signaling-related genes. Consistently, Akt phosphorylation was also decreased in Rgc32-/- iWAT, which led to an increase in β3-adrenergic receptor expression and subsequent activation of mTORC1. β3-adrenergic receptor antagonist SR 59230A and mTORC1 inhibitor rapamycin blocked the Rgc32 deficiency-induced thermogenic gene expression in iWAT both in vitro and in vivo. These results indicate that RGC-32 suppressed iWAT thermogenic gene expression through down-regulation of β3-AR expression and mTORC1 activity via a PI3K/Akt-dependent mechanism.

Response gene to complement 32 interacts with SMAD3 to promote TGF-β-induced extracellular matrix production in multiple sclerosis

Abstract We have previously shown that response gene to complement 32 (RGC-32) mediates transforming growth factor-β (TGF-β)-induced astrocyte reactivity and extracellular matrix production. However, the molecular mechanisms underlying RGC-32 expression and function remain to be elucidated. In the present study, we found that TGF-β induced expression and nuclear translocation of both RGC-32 and SMAD3 in astrocytes. Using specific pathways inhibitors, we have found that RGC-32 induction is mediated by SMAD-dependent and independent mechanisms. We investigated whether RGC-32 interacts with SMAD2 or SMAD3 in astrocytes and if this association plays a role in extracellular matrix synthesis. Co-immunoprecipitation showed that SMAD3, but not SMAD2 physically interacts with RGC-32 in astrocytes. SIS3, an inhibitor of SMAD3 phosphorylation, significantly reduced RGC-32 translocation to the nucleus, indicating that SMAD3 phosphorylation is required for RGC-32 nuclear translocation. On the other hand, silencing RGC-32 with siRNA had no effect on SMAD3 nuclear translocation. Y27632, a selective ROCK inhibitor was also able to significantly inhibit RGC-32 nuclear translocation, while the SMAD3 nuclear translocation was unaffected. The inhibition of SMAD3 phosphorylation also blocked the RGC-32-induced collagen type I expression, indicating a synergistic action between RGC-32 and SMAD3 to induce the expression of collagen type I. Taken together, our data demonstrate for the first time that RGC-32 interacts with SMAD3 to mediate the extracellular matrix production in astrocytes. These data suggest that a similar mechanism might be involved in mediation of gliosis seen in chronic multiple sclerosis lesions.

RGC32 Promotes Bleomycin-Induced Systemic Sclerosis in a Murine Disease Model by Modulating Classically Activated Macrophage Function.

Systemic sclerosis (SSc) is a multisystem autoimmune disorder that is characterized by inflammation and fibrosis in the skin and internal organs. Previous studies indicate that inflammatory cells and cytokines play essential roles in the pathogenesis of SSc; however, the mechanisms that underlie the inflammation-driven development of SSc are not fully understood. In this study, we show that response gene to complement 32 (RGC32) is abundantly expressed in mouse macrophages in the early stage of bleomycin-induced SSc. Importantly, RGC32 is required to induce the inflammatory response during the onset of SSc, because RGC32 deficiency in mice significantly ameliorates skin and lung sclerosis and inhibits the expression of inflammatory mediators inducible NO synthase (iNOS) and IL-1β in macrophages. RGC32 appears to be a novel regulator for the differentiation of classically activated macrophages (M1 macrophages). IFN-γ and LPS stimulation induces RGC32 expression in primary peritoneal macrophages and bone marrow-derived macrophages. RGC32 deficiency impairs the polarization of M1 macrophages and attenuates iNOS and IL-1β production. Mechanistically, RGC32 interacts with NF-κB proteins and promotes iNOS and IL-1β expression by binding to their promoters. Collectively, our data reveal that RGC32 promotes the onset of SSc by regulating the inflammatory response of M1 macrophages, and it may serve as a promising therapeutic target for treating SSc.

Pumilio directs deadenylation-associated translational repression of the cyclin-dependent kinase 1 activator RGC-32.

Response gene to complement-32 (RGC-32) activates cyclin-dependent kinase 1, regulates the cell cycle and is deregulated in many human tumours. We previously showed that RGC-32 expression is upregulated by the cancer-associated Epstein-Barr virus (EBV) in latently infected B cells through the relief of translational repression. We now show that EBV infection of naïve primary B cells also induces RGC-32 protein translation. In EBV-immortalised cell lines, we found that RGC-32 depletion resulted in cell death, indicating a key role in B cell survival. Studying RGC-32 translational control in EBV-infected cells, we found that the RGC-32 3′untranslated region (3′UTR) mediates translational repression. Repression was dependent on a single Pumilio binding element (PBE) adjacent to the polyadenylation signal. Mutation of this PBE did not affect mRNA cleavage, but resulted in increased polyA tail length. Consistent with Pumilio-dependent recruitment of deadenylases, we found that depletion of Pumilio in EBV-infected cells increased RGC-32 protein expression and polyA tail length. The extent of Pumilio binding to the endogenous RGC-32 mRNA in EBV-infected cell lines also correlated with RGC-32 protein expression. Our data demonstrate the importance of RGC-32 for the survival of EBV-immortalised B cells and identify Pumilio as a key regulator of RGC-32 translation.

RGC32 induces epithelial-mesenchymal transition by activating the Smad/Sip1 signaling pathway in CRC

Response gene to complement 32 (RGC32) is a transcription factor that regulates the expression of multiple genes involved in cell growth, viability and tissue-specific differentiation. However, the role of RGC32 in tumorigenesis and tumor progression in colorectal cancer (CRC) has not been fully elucidated. Here, we showed that the expression of RGC32 was significantly up-regulated in human CRC tissues versus adjacent normal tissues. RGC32 expression was significantly correlated with invasive and aggressive characteristics of tumor cells, as well as poor survival of CRC patients. We also demonstrated that RGC32 overexpression promoted proliferation, migration and tumorigenic growth of human CRC cells in vitro and in vivo. Functionally, RGC32 facilitated epithelial-mesenchymal transition (EMT) in CRC via the Smad/Sip1 signaling pathway, as shown by decreasing E-cadherin expression and increasing vimentin expression. In conclusion, our findings suggested that overexpression of RGC32 facilitates EMT of CRC cells by activating Smad/Sip1 signaling.

Abstract 211: Response Gene to Complement 32 Deficiency Protects Endothelial Cell From Inflammation and Attenuates Atheroslcerosis

Response gene to complement 32 (RGC-32) is involved in diet-induced obesity and hepatic steatosis. Therefore, we hypothesized that RGC-32 plays a role in atherosclerosis. Our current study showed that RGC-32 expression was dramatically induced in endothelial cells (ECs) of the atherosclerotic lesions from both apolipoprotein E-deficient (ApoE -/- ) mice and diseased human arteries. RGC-32 deficiency (Rgc32 -/- ) significantly attenuated the high-fat diet-induced and spontaneously developed atherogenesis in ApoE -/- mice without affecting the serum lipid profiles. In addition, Rgc32 -/- decreased the macrophage content without affecting fibrous cap size. Rgc32 -/- in bone marrow cells had no effect on atherosclerosis development, and Rgc32 -/- mice transplanted with wild-type (WT) bone marrow cells exhibited decreased atherosclerotic lesion area and macrophage infiltration, suggesting that RGC-32 in resident vascular cells plays a critical role in the atherogenesis. Rgc32 -/- decreased the expression of intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) in ECs both in vivo and in vitro , resulting in a decreased monocyte-EC interaction. Mechanistically, RGC-32 regulated ICAM-1 and VCAM-1 transcription via activation of nuclear factor (NF)-κB. It appeared that RGC-32 interacted with NF-κB, which facilitated NF-κB binding to ICAM-1 and VCAM-1 promoters. Indeed, blockade of NF-κB activity by its selective inhibitor ammonium pyrrolidinedithiocarbamate blocked RGC-32-induced ICAM-1 and VCAM-1 expression. In conclusion, RGC-32 promoted atherogenesis by inducing monocyte-EC interaction through NF-κB-dependent induction of endothelial ICAM-1 and VCAM-1 expression.

Response gene to complement 32 regulates the G2/M phase checkpoint during renal tubular epithelial cell repair.

BackgroundThe aim of this study was to evaluate the influence of RGC-32 (response gene to complement 32) on cell cycle progression in renal tubular epithelial cell injury.MethodsNRK-52E cells with overexpressed or silenced RGC-32 were constructed via transient transfection with RGC-32 expression plasmid and RGC-32 siRNA plasmid, and the cell cycle distribution was determined. The expression levels of fibrosis factors, including smooth muscle action (α-SMA), fibronectin (FN) and E-cadherin, were assessed in cells with silenced RGC-32.ResultsThe cells were injured via TNF-α treatment, and the injury was detectable by the enhanced expression of neutrophil gelatinase-associated lipocalin (NGAL). RGC-32 expression also increased significantly. The number of cells at G2/M phase increased dramatically in RGC-32 silenced cells, indicating that RGC-32 silencing induced G2/M arrest. In addition, after treatment with TNF-α, the NRK-52E cells with silenced RGC-32 showed significantly increased expression of α-SMA and FN, but decreased expression of E-cadherin.ConclusionsThe results of this study suggest that RGC-32 probably has an important impact on the repair process of renal tubular epithelial cells in vitro by regulating the G2/M phase checkpoint, cell fibrosis and cell adhesion. However, the exact mechanism needs to be further elucidated.

Abstract 638: Response Gene to Complement 32 Promotes Atherosclerosis Through Endothelial Cell Dysfunction Induced Vascular Inflammation

Atherosclerosis is the major cause of cardiovascular diseases and the primary cause of death worldwide. Our previous studies have demonstrated that response gene to complement 32 (RGC-32) deficiency prevents the mice from high-fat diet-induced obesity and insulin resistance. The present study was conducted to determine the role of RGC-32 in the development of atherosclerosis. We observed that endothelial RGC-32 expression was dramatically induced in human and mouse atherosclerotic lesions. RGC-32 deficiency (RGC-32-/-) significantly attenuated the atherosclerotic lesion formation in arteries of ApoE-/- mice. Mechanistically, RGC-32-/- diminished the expression of vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule (ICAM)-1 in primary cultured mouse endothelial cells induced by tumor necrosis factor (TNF)-α. RGC-32-/- also inhibited TNF-α-induced monocyte-endothelial cell interaction. These data demonstrate that RGC-32 contributes to the development of atherosclerosis by regulating the expression of endothelial adhesive molecules, and thus facilitating macrophage infiltration. Therefore, RGC-32 may be a potential novel drug target in the treatment of atherosclerosis and its related cardiovascular diseases.

The expression of response gene to complement 32 on renal ischemia reperfusion injury in rat

To investigate the expression of response gene to complement 32 (RGC32) in rat with acute kidney injury (AKI) and to explore the role of RGC32 in renal injury and repair induced by ischemia reperfusion. Rats were randomly divided into two groups, including sham operation group (n = 48) and acute ischemia reperfusion injury (IRI) group (n = 48). Rats were sacrificed following reperfusion 2 h, 6 h, 24 h, 48 h, 72 h, 1 week (w), 2 w, and 4 w. The distribution and expression of RGC32 in renal tissue were observed by means of immunohistochemistry. The mean density of the images detected by Image-Pro Plus 6 was designated as the representative RGC32 expression levels. Meanwhile, RGC32 mRNA expression was measured by qPCR. RGC32 mainly expressed in cytoplasm of proximal tubular epithelial cells. However, RGC32 did not express in renal interstitium and vessels. The expression levels of RGC32 measured by immunohistochemistry at different reperfusion time were 0.0168 ± 0.0029, 0.0156 ± 0.0021, 0.0065 ± 0.0013, 0.0075 ± 0.0013, 0.0096 ± 0.0014, 0.0132 ± 0.0016, 0.0169 ± 0.0014, 0.0179 ± 0.0022, respectively. Compared with the sham group, the level of RGC32 expression in IRI group was significant lower at 24 h, 48 h, 72 h after IRI (p < 0.05). The expression levels of RGC32 mRNA at different reperfusion time measured by qPCR were corroborated the immunohistochemistry finding. The in vitro experiments show the expression of α-SMA and extracellular matrix expression increased signification when the RGC32 was silenced. Our data showed that the RGC32 expression in AKI rat decreased significantly reduces with different reperfusion time and performs a time-dependent manner. RGC32 may play an important role in the pathogenesis of AKI following IRI and repair in rat.

RGC-32 Deficiency Protects against Hepatic Steatosis by Reducing Lipogenesis

Hepatic steatosis is associated with insulin resistance and metabolic syndrome because of increased hepatic triglyceride content. We have reported previously that deficiency of response gene to complement 32 (RGC-32) prevents high-fat diet (HFD)-induced obesity and insulin resistance in mice. This study was conducted to determine the role of RGC-32 in the regulation of hepatic steatosis. We observed that hepatic RGC-32 was induced dramatically by both HFD challenge and ethanol administration. RGC-32 knockout (RGC32(-/-)) mice were resistant to HFD- and ethanol-induced hepatic steatosis. The hepatic triglyceride content of RGC32(-/-) mice was decreased significantly compared with WT controls even under normal chow conditions. Moreover, RGC-32 deficiency decreased the expression of lipogenesis-related genes, sterol regulatory element binding protein 1c (SREBP-1c), fatty acid synthase, and stearoyl-CoA desaturase 1 (SCD1). RGC-32 deficiency also decreased SCD1 activity, as indicated by decreased desaturase indices of the liver and serum. Mechanistically, insulin and ethanol induced RGC-32 expression through the NF-κB signaling pathway, which, in turn, increased SCD1 expression in a SREBP-1c-dependent manner. RGC-32 also promoted SREBP-1c expression through activating liver X receptor. These results demonstrate that RGC-32 contributes to the development of hepatic steatosis by facilitating de novo lipogenesis through activating liver X receptor, leading to the induction of SREBP-1c and its target genes. Therefore, RGC-32 may be a potential novel drug target for the treatment of hepatic steatosis and its related diseases.

Abstract 325: Response Gene to Complement 32 Deficiency Protects Against Hepatic Steatosis by Inhibiting Lipogenesis in Mice

Hepatic steatosis is associated with obesity due to the increased lipogenesis. Previously, we have found that RGC-32 (response gene to complement 32) deficiency prevents the mice from high-fat diet (HFD)-induced obesity and insulin resistance. The present study was conducted to determine the role of RGC-32 in the control of hepatic steatosis. We observed that hepatic RGC-32 expression was dramatically induced by HFD challenge. RGC-32 knockout (RGC32-/-) mice were resistant to HFD-induced hepatic steatosis. More importantly, hepatic triglyceride contents of RGC32-/- mice were significantly decreased compared with wild-type (WT) controls on both normal chow and HFD. Mechanistically, RGC-32 deficiency decreased expression of lipogenesis-related genes, sterol regulatory element (SRE) binding protein (SREBP)-1c, fatty acid synthase (FAS) and stearoyl-CoA desaturase-1 (SCD1). Our in vitro study showed that RGC-32 knockdown decreased while RGC-32 overexpression increased SCD1 expression in hepatocytes. Deletion or mutation of SRE in the SCD1 promoter abolished the function of RGC-32. These data demonstrate that RGC-32 contributes to HFD-induced hepatic steatosis by facilitating de novo lipogenesis in a SREBP-1c dependent manner. Therefore, RGC-32 may be a novel drug target in the treatment of hepatic steatosis and its related diseases.

Expression of RGC32 in human normal and preeclamptic placentas and its role in trophoblast cell invasion and migration

IntroductionPreeclampsia (PE) is a pregnancy-specific complication and it is related to insufficient extravillous trophoblast invasion. To date, the pathophysiology of PE has not yet been fully elucidated. Response gene to complement 32 (RGC32) is a novel cellular protein, and it plays important roles in the regulation of cell differentiation, angiogenesis, migration, and invasion. This study aimed to determine the RGC32 expression and function in human placentas and to explore the underlying mechanisms. MethodsRGC32 expression in term placentas collected after cesarean section from pregnant women with PE and normal pregnant women was determined by real-time reverse transcriptase polymerase chain reaction (RT-PCR), Western blot, and immunohistochemistry. The effects of RGC32 expression on trophoblast invasion, migration, and the underlying mechanisms were studied in HTR8/SVneo cells. ResultsThe messenger RNA (mRNA) and protein levels of RGC32 were significantly downregulated in preeclamptic placentas compared with normal controls (P < 0.05). RGC32 silencing significantly inhibited HTR8/SVneo cell migration and invasion (P < 0.001, respectively). These effects were associated with decreased activities and expression of matrix metalloproteinase (MMP)-2/9, and with the reduced phosphorylation level of Akt. DiscussionRGC32 may play important roles in the pathophysiology of PE by directly affecting the invasion/migration of trophoblast.

Response gene to complement 32 (RGC-32) expression on M2-polarized and tumor-associated macrophages is M-CSF-dependent and enhanced by tumor-derived IL-4.

Response gene to complement 32 (RGC-32) is a cell cycle regulator involved in the proliferation, differentiation and migration of cells and has also been implicated in angiogenesis. Here we show that RGC-32 expression in macrophages is induced by IL-4 and reduced by LPS, indicating a link between RGC-32 expression and M2 polarization. We demonstrated that the increased expression of RGC-32 is characteristic of alternatively activated macrophages, in which this protein suppresses the production of pro-inflammatory cytokine IL-6 and promotes the production of the anti-inflammatory mediator TGF-β. Consistent with in vitro data, tumor-associated macrophages (TAMs) express high levels of RGC-32, and this expression is induced by tumor-derived ascitic fluid in an M-CSF- and/or IL-4-dependent manner. Collectively, these results establish RGC-32 as a marker for M2 macrophage polarization and indicate that this protein is a potential target for cancer immunotherapy, targeting tumor-associated macrophages.

C5a stimulates the proliferation of breast cancer cells via Akt-dependent RGC-32 gene activation

Complement system activation contributes to various immune and inflammatory diseases, as well as cancers.However, the role of complement activation in the proliferation of cancer cells is not clear. In the present study, we investigated the consequences of complement activation on the proliferation of breast cancer cells and its possible mechanisms. We focused our study on the potential roles of the anaphylatoxins C3a and C5a in the proliferation of human breast cancer, as two important immune mediators generated after complement activation. Our study revealed that C5a stimulation, but not C3a, enhanced the proliferation of human breast cancer cells in vitro. Moreover, the expression of response gene to complement 32 (RGC-32) was pronounced in breast cancer cells in response to C5a stimulation. Notably, blockade of the C5a receptor markedly reduced the expression of RGC-32 and the proliferation of breast cancer cells stimulated by C5a. Meanwhile, silencing of RGC-32 expression reduced the proliferation of breast cancer cells induced by C5a treatment. Further investigation revealed that Akt activation was involved in C5a-induced RGC-32 expression and breast cancer cell proliferation. In conclusion, the present study indicates that C5a may promote the proliferation of breast cancer cells through Akt1 activation of the RGC-32 gene.

Knockdown of response gene to complement 32 (RGC32) induces apoptosis and inhibits cell growth, migration, and invasion in human lung cancer cells.

Response gene to complement 32 (RGC32) is a novel protein originally identified as a cell cycle activator and has been demonstrated to be overexpressed in a variety of human malignancies, including lung cancer. However, the potential role of RGC32 in lung cancer initiation and progression remains to be elucidated. In the present study, RNA interference mediated by plasmid expressing RGC32 short-hairpin RNA (shRNA) was utilized to knockdown RGC32 expression in human lung cancer LTE cells. We found that the mRNA and protein expression levels of RGC32 were significantly decreased in RGC32-specific shRNA-transfected cells in comparison with the untransfected and control shRNA-transfected cells. Furthermore, knockdown of RGC32 dramatically reduced cell proliferation, colony formation, and invasion and migration capacities of LTE cells in vitro. Specific down-regulation of RGC32 caused G0/G1 cell cycle arrest and eventual apoptosis. Meanwhile, Western blot analysis indicated that cells with stably knockdown of RGC32 showed decreased expression levels of Cyclin D1, Cyclin E, Bcl-2, matrix metalloproteinase (MMP)-2, and MMP-9, but increased expression levels of activate caspase-3, Bax, and cleaved poly (ADP-ribose) polymerase (PARP) in comparison with control shRNA-transfected cells. Taken together, our data suggest that RGC32 is involved in tumorigenesis of human lung cancer and may serve as a promising therapeutic target for lung cancer.

Response Gene to Complement 32 Is Essential for Fibroblast Activation in Renal Fibrosis

Response gene to complement 32 (RGC-32) is a downstream target of transforming growth factor-β (TGF-β). TGF-β is known to play a pathogenic role in renal fibrosis. In this study, we investigated RGC-32 function in renal fibrosis following unilateral ureteral obstruction (UUO) in mice, a model of progressive tubulointerstitial fibrosis. RGC-32 is normally expressed only in blood vessels of mouse kidney. However, UUO induces RGC-32 expression in renal interstitial cells at the early stage of kidney injury, suggesting that RGC-32 is involved in interstitial fibroblast activation. Indeed, expression of smooth muscle α-actin (α-SMA), an indicator of fibroblast activation, is limited to the interstitial cells at the early stage, and became apparent later in both interstitial and tubular cells. RGC-32 knockdown by shRNA significantly inhibits UUO-induced renal structural damage, α-SMA expression and collagen deposition, suggesting that RGC-32 is essential for the onset of renal interstitial fibrosis. In vitro studies indicate that RGC-32 mediates TGF-β-induced fibroblast activation. Mechanistically, RGC-32 interacts with Smad3 and enhances Smad3 binding to the Smad binding element in α-SMA promoter as demonstrated by DNA affinity assay. In the chromatin setting, Smad3, but not Smad2, binds to α-SMA promoter in fibroblasts. RGC-32 appears to be essential for Smad3 interaction with the promoters of fibroblast activation-related genes in vivo. Functionally, RGC-32 is crucial for Smad3-mediated α-SMA promoter activity. Taken together, we identify RGC-32 as a novel fibrogenic factor contributing to the pathogenesis of renal fibrosis through fibroblast activation.

Response Gene to Complement 32 Promotes Vascular Lesion Formation Through Stimulation of Smooth Muscle Cell Proliferation and Migration

The objectives of this study were to determine the role of response gene to complement 32 (RGC-32) in vascular lesion formation after experimental angioplasty and to explore the underlying mechanisms. Using a rat carotid artery balloon-injury model, we documented for the first time that neointima formation was closely associated with a significantly increased expression of RGC-32 protein. Short hairpin RNA knockdown of RGC-32 via adenovirus-mediated gene delivery dramatically inhibited the lesion formation by 62% as compared with control groups 14 days after injury. Conversely, RGC-32 overexpression significantly promoted the neointima formation by 33%. Gain- and loss-of-function studies in primary culture of rat aortic smooth muscle cells (RASMCs) indicated that RGC-32 is essential for both the proliferation and migration of RASMCs. RGC-32 induced RASMC proliferation by enhancing p34(CDC2) activity. RGC-32 stimulated the migration of RASMC by inducing focal adhesion contact and stress fiber formation. These effects were caused by the enhanced rho kinase II-α activity due to RGC-32-induced downregulation of Rad GTPase. RGC-32 plays an important role in vascular lesion formation following vascular injury. Increased RGC-32 expression in vascular injury appears to be a novel mechanism underlying the migration and proliferation of vascular smooth muscle cells. Therefore, targeting RGC-32 is a potential therapeutic strategy for the prevention of vascular remodeling in proliferative vascular diseases.