OBJECTIVETo investigate the significance of Rac subfamily members in the gastrointestinal carcinogenesis and progression.

METHODSThe mRNA expression of Rac1, Rac2 and Rac3 in 12 kinds of gastrointestinal cancer cell lines was examined by semi-quantitative RT-PCR. The activities of Rac1 protein in 5 kinds of gastric cancer cell lines were tested by pull-down assay.

RESULTSCompared with the normal gastric mucosa and intestinal epithelial cell line, the mRNA expression of Rac1 and Rac3 was up-regulated in most of gastrointestinal cancer cell lines. The activities of Rac1 protein increased markedly in gastric cancer cell lines.

CONCLUSIONThe increased mRNA expression of Rac1 and Rac3 in gastrointestinal cancer cell lines and the abnormal activation of Rac1 protein in gastric cancer cell lines might be correlated with the carcinogenesis of gastrointestinal cancer.

Cell Line, Tumor ; Gastrointestinal Neoplasms ; metabolism ; Humans ; RNA, Messenger ; analysis ; Reverse Transcriptase Polymerase Chain Reaction ; rac GTP-Binding Proteins ; genetics ; rac1 GTP-Binding Protein ; analysis ; genetics

It is far from understood why we forget things that are known to us seconds ago. Emerging evidence emphasizes that small G protein Rac could be a key to understanding this type of rapid early memory forgetting. This current perspective article will first review these studies and then discuss their implications for the internal processes underlying forgetting.
Animals ; Drosophila Proteins ; physiology ; Drosophila melanogaster ; physiology ; Humans ; Memory ; physiology ; Oxidation-Reduction ; Retention (Psychology) ; Signal Transduction ; rac GTP-Binding Proteins ; physiology

Up-regulation of intercellular adhesion molecule-1 (ICAM-1) in the lung airway epithelium is associated with the epithelium-leukocyte interaction, critical for the pathogenesis of various lung airway inflammatory diseases such as asthma. However, little is known about how ICAM-1 is up-regulated in human airway epithelial cells. In this study, we show that tumor TNF-alpha induces monocyte adhesion to A549 human lung airway epithelium and also up-regulation of ICAM-1 expression. These effects were significantly diminished by pre-treatment with diphenyliodonium (DPI), an inhibitor of NADPH oxidase-like flavoenzyme. In addition, the level of reactive oxygen species (ROS) was increased in response to TNF-alpha in A549 cells, suggesting a potential role of ROS in the TNF-alpha-induced signaling to ICAM-1 expression and monocyte adhesion to airway epithelium. Further, we found out that expression of Rac(N17), a dominant negative mutant of Rac1, suppressed TNF-alpha-induced ROS generation, ICAM-1 expression, and monocyte adhesion to airway epithelium. These findings suggest that Rac1 lies upstream of ROS generation in the TNF-alpha-induced signaling to ICAM-1 expression in airway epithelium. Finally, pretreatment with pyrrolidine dithiocarbamate (PDTC), an inhibitor of NF-kappaB, reduced TNF-alpha-induced ICAM-1 expression and both DPI and Rac(N17) significantly diminished NF-kappaB activation in response to TNF-alpha. Together, we propose that Rac1-ROS-linked cascade mediate TNF-alpha-induced ICAM-1 up-regulation in the airway epithelium via NF-kappaB-dependent manner.
Cell Line ; Electrophoresis, Polyacrylamide Gel ; Epithelial Cells/metabolism ; Humans ; Intercellular Adhesion Molecule-1/*physiology ; Microscopy, Confocal ; Trachea/cytology/*metabolism ; Tumor Necrosis Factor-alpha/*physiology ; Up-Regulation/*physiology ; rac GTP-Binding Proteins/*metabolism

AMP-activated protein kinase (AMPK) is a metabolic sensor activated during metabolic stress and it regulates various enzymes and cellular processes to maintain metabolic homeostasis. We previously reported that activation of AMPK by glucose deprivation (GD) and leptin increases KATP currents by increasing the surface levels of KATP channel proteins in pancreatic beta-cells. Here, we show that the signaling mechanisms that mediate actin cytoskeleton remodeling are closely associated with AMPK-induced KATP channel trafficking. Using F-actin staining with Alexa 633-conjugated phalloidin, we observed that dense cortical actin filaments present in INS-1 cells cultured in 11 mM glucose were disrupted by GD or leptin treatment. These changes were blocked by inhibiting AMPK using compound C or siAMPK and mimicked by activating AMPK using AICAR, indicating that cytoskeletal remodeling induced by GD or leptin was mediated by AMPK signaling. AMPK activation led to the activation of Rac GTPase and the phosphorylation of myosin regulatory light chain (MRLC). AMPK-dependent actin remodeling induced by GD or leptin was abolished by the inhibition of Rac with a Rac inhibitor (NSC23766), siRac1 or siRac2, and by inhibition of myosin II with a myosin ATPase inhibitor (blebbistatin). Immunocytochemistry, surface biotinylation and electrophysiological analyses of KATP channel activity and membrane potentials revealed that AMPK-dependent KATP channel trafficking to the plasma membrane was also inhibited by NSC23766 or blebbistatin. Taken together, these results indicate that AMPK/Rac-dependent cytoskeletal remodeling associated with myosin II motor function promotes the translocation of KATP channels to the plasma membrane in pancreatic beta-cells.
AMP-Activated Protein Kinases/metabolism ; Actins/*metabolism ; Animals ; Cell Line ; Glucose/metabolism ; Insulin-Secreting Cells/*metabolism ; KATP Channels/*metabolism ; Leptin/metabolism ; Myosin Type II/*metabolism ; Phosphorylation ; Rats ; *Signal Transduction ; rac GTP-Binding Proteins/*metabolism

Metformin is currently a strong candidate anti-tumor agent in multiple cancers. However, its anti-tumor effectiveness varies among different cancers or subpopulations, potentially due to tumor heterogeneity. It thus remains unclear which hepatocellular carcinoma (HCC) patient subpopulation(s) can benefit from metformin treatment. Here, through a genome-wide CRISPR-Cas9-based knockout screen, we find that DOCK1 levels determine the anti-tumor effects of metformin and that DOCK1 is a synthetic lethal target of metformin in HCC. Mechanistically, metformin promotes DOCK1 phosphorylation, which activates RAC1 to facilitate cell survival, leading to metformin resistance. The DOCK1-selective inhibitor, TBOPP, potentiates anti-tumor activity by metformin in vitro in liver cancer cell lines and patient-derived HCC organoids, and in vivo in xenografted liver cancer cells and immunocompetent mouse liver cancer models. Notably, metformin improves overall survival of HCC patients with low DOCK1 levels but not among patients with high DOCK1 expression. This study shows that metformin effectiveness depends on DOCK1 levels and that combining metformin with DOCK1 inhibition may provide a promising personalized therapeutic strategy for metformin-resistant HCC patients.
Animals ; Antineoplastic Agents/therapeutic use* ; Carcinoma, Hepatocellular/metabolism* ; Cell Line, Tumor ; Clustered Regularly Interspaced Short Palindromic Repeats ; Genome ; Humans ; Liver Neoplasms/metabolism* ; Metformin/therapeutic use* ; Mice ; Phosphorylation ; Synthetic Lethal Mutations ; Transcription Factors/metabolism* ; rac GTP-Binding Proteins/metabolism*

Previously, we reported that CD40-induced production of reactive oxygen species (ROS) by NADPH oxidase requires the TNF receptor-associated factor (TRAF) 3, as well as the activities of phosphatidylinositol 3-kinase (PI3K) and Rac1. Here we investigated the possible mechanisms of the production of ROS after CD40 ligation in B cells. We describe an alternative ROS production pathway that is triggered by CD40 ligation, involves 5-lipoxygenase (5-LO), and results in activation of p38 MAPK. Our studies in Raji human B lymphomas revealed that CD40-induced ROS production by 5-LO also requires the activities of PI3K and Rac1. In contrast to the NADPH oxidase pathway, however, TRAF molecules are not required for the CD40-induced ROS production by 5-LO. The association of CD40 with 5-LO is dependent on CD40 ligation in Raji B cells, and co-immunoprecipitation experiments using epitope-tagged proteins transiently expressed in human embryonic kidney 293T cells revealed the role of the regulatory subunit of PI3K, p85, in this association. Collectively, these data suggest a separate pathway for the CD40-induced ROS production in B cells and demonstrate that this pathway requires 5-LO via direct association of p85 with both CD40 and 5-LO.
Antigens, CD40/*metabolism ; Arachidonate 5-Lipoxygenase/*metabolism ; B-Lymphocytes/*enzymology/immunology ; CD40 Ligand/metabolism ; Cell Line, Tumor ; *Enzyme Activation ; HEK293 Cells ; Humans ; Phosphatidylinositol 3-Kinases/metabolism ; Protein Binding ; *Reactive Oxygen Species/metabolism ; Signal Transduction ; p38 Mitogen-Activated Protein Kinases/*metabolism ; rac GTP-Binding Proteins/metabolism

The aim of this study was to investigate the role of RhoA/mDia1 pathway in the process of thrombin-induced platelet aggregation and regulatory effect of PI3K inhibitor on this process. The human platelets were isolated from peripheral blood, the activation of RhoA, Rac1 and Cdc42 in the platelet aggregation was detected by GST pull-down assay and immune co-precipitation, the interaction of RhoA, Rac1 and Cdc42 with mDia1 and the formation of complex in the process of platelet aggregation were determined by immune coprecipitation, and the effect of PI3K inhibitor (wortmannin) on above-mentioned process was assayed. The results showed that thrombin elevated the activity of RhoA and the binding capability of RhoA with mDia1 during thrombin-induced platelet aggregation and spreading on Fg coated coverslips. Wortmannin inhibited the rising of RhoA activity and the binding level of RhoA with mDia1 induced by thrombin. Thrombin elevated the activity of Rac1 and Cdc42 during thrombin-induced platelet aggregation, but could not induce binding of Rac1 or Cdc42 with mDia1. Wortmannin could not inhibit the rising of Rac1 and Cdc42 activity induced by thrombin. It is concluded that the PI3-kinase regulates the thrombin-induced actin cytoskeleton reconstitution in platelets by RhoA-mDia1 pathway.
Actins ; metabolism ; pharmacology ; Adaptor Proteins, Signal Transducing ; immunology ; metabolism ; Blood Platelets ; metabolism ; Cells, Cultured ; Humans ; Phosphatidylinositol 3-Kinases ; pharmacology ; Platelet Aggregation ; drug effects ; Thrombin ; pharmacology ; rac1 GTP-Binding Protein ; metabolism ; rhoA GTP-Binding Protein ; metabolism ; pharmacology

Brain ; Cholesterol ; chemistry ; Cytoskeleton ; drug effects ; Endothelial Cells ; cytology ; metabolism ; Hemolysin Proteins ; chemistry ; pharmacology ; Humans ; Phalloidine ; pharmacology ; Pseudopodia ; drug effects ; Stress Fibers ; drug effects ; rac1 GTP-Binding Protein ; metabolism ; rhoA GTP-Binding Protein ; metabolism

OBJECTIVETo investigate modulatory role of Rac1 protein in epidermal stem cell (ESC) migration during wound healing, in order to provide a reference for enriching basic theory of wound healing and guiding clinical application.

METHODSConstitutively active mutant of Rac1 protein (Rac1Q61L) or dominant negative isoform of Rac1 protein (Rac1T17N) was transfected into ESC using a retroviral vector FUGW, and retroviral vector FUGW transfected into ESC in singles was used as blank control. The cells were divided into 3 parts according to the random number table and treated as follows. First, equal numbers of cells were inoculated into 24-well plates coated with collagen I (20 µg/mL), collagen IV (20 µg/mL) or fibronectin (10 µg/mL). Cells adhered to above matrices were quantitated using CytoTox 96 colorimetric kit. Second, 1000 cells adhered to collagen IV, after being stained with tetramethyl rhodamine isothiocyanate-phalloidin, were collected for observation of cell morphology and comparison of spreading area under confocal laser scanning microscope. Third, ESC with density of 2 × 10(5) cells per well were placed in upper compartment of Transwell chamber, DK-SFM culture medium alone or that containing stromal cell derived factor 1 (SDF-1) was added into lower compartment of Transwell chamber. Migration of ESC was observed using inverted phase contrast microscope, and the result was denoted as migration rate. Lastly, ESC with density of 7.5 × 10(5) cells per well was inoculated into 6-well plates for 12 hours, and treated with 4 µg/mL mitomycin C for 2 hours. The remaining scratch width of monolayer was respectively measured 6 hours or 12 hours after scratching to calculate the percentage of remaining scratch width. Data were processed with t test.

RESULTSCompared with that of blank control, the number of Rac1Q61L-transfected cells adhered to collagen I was significantly increased (t = 5.302,P < 0.05), while the number of Rac1T17N-transfected cells adhered to collagen I, IV, and fibronectin were all obviously decreased (with t value respectively 13.741, 15.676, 8.256, P values all below 0.05). Confocal laser scanning microscope showed that spreading area of Rac1Q61L-transfected ESC (with laminate pseudopodia on edge) and Rac1T17N-transfected ESC was respectively larger and smaller as compared with that of blank control. With SDF-1 effect, the migration rate of Rac1T17N-transfected ESC was decreased by 78.0% and Rac1Q61L-transfected ESC was increased by 43.4% as compared with that of blank control. Without SDF-1 effect, the migration rate of Rac1T17N-transfected ESC was decreased by 55.2%, while the migration rate of Rac1Q61L-transfected ESC was close to that of blank control. Six or 12 hours after scratching, the percentage of remaining scratch width in Rac1Q61L-transfected ESC was lower as compared with that in blank control [(39 ± 9)% vs. (43 ± 5)%, (6 ± 5)% vs. (18 ± 7)%, with t value respectively 1.027, 4.389, with P value respectively above and below 0.05], while that in Rac1T17N-transfected ESC [(81 ± 9)%, (71 ± 11)%, respectively] was obviously higher as compared with that in blank control (with t value respectively 11.386, 11.726, P values all below 0.05).

CONCLUSIONSRac1 protein may control the migration of ESC by regulating its adhesion, spreading, and chemotaxis, and it plays an active role in wound healing accelerated by ESC.

Cell Movement ; Cell Proliferation ; Epidermis ; cytology ; Epithelial Cells ; Humans ; Mutation ; Stem Cells ; cytology ; Transfection ; Wound Healing ; rac1 GTP-Binding Protein ; genetics ; metabolism

BACKGROUNDThe release of Weibel-Palade Bodies (WPB) is a form of endothelial cell activation. But the signal transduction pathway leading to WPB release is not yet defined. We hypothesized that small G-protein rac1 and reactive oxygen species (ROS) mediate the ligand induced release of Weibel-Palade Bodies.

METHODSWe tested this hypothesis by using wild-type and mutant adenoviral rac1 expression vectors, and by manipulating the production and destruction of superoxide and hydrogen peroxide in human aortic endothelial cells (HAEC).

RESULTSThrombin (1.0 Unit, 30 min) induced the increase of WPB release by 3.7-fold in HAEC, and that H2O2 (0.1 mmol/L, 30 min) induced by 4.5-fold. These results correlated with thrombin-stimulated activation of rac-GTP binding activity by 3.5-fold, and increase of ROS production by 3.4-fold. The dominant negative adenoviral rac-N17 gene transfer dramatically inhibited the release of WPB by 64.2% (control) and 77.3% (thrombin-stimulation), and decreased ROS production by 65.5% (control) and 83.6% (thrombin-stimulation) compared with non-infected cells, respectively. Anti-oxidants, catalase and N-acetyl-cysteine significantly decreased the release of WPB by 34% and 79% in control cells, and further decreased by 63.6% and 46.7% in rac-N17 transferred cells compared with non-infected cells. We also confirmed that rac1 was located upstream of ROS in the WPB release pathway.

CONCLUSIONSSmall G-protein rac1 medicates ligand-induced release of Weibel-Palade Bodies in human aortic endothelial cells, and the signal pathway of WPB release is a rac1-dependent ROS regulating mechanism.

Aorta ; ultrastructure ; Endothelial Cells ; ultrastructure ; Humans ; Reactive Oxygen Species ; Signal Transduction ; Thrombin ; pharmacology ; Weibel-Palade Bodies ; physiology ; rac1 GTP-Binding Protein ; physiology