Tiam1 mediates Rac1 activation and contraction-induced glucose uptake in skeletal muscle cells

S-Nitrosylation of Septin2 Exacerbates Aortic Aneurysm and Dissection by Coupling the TIAM1-RAC1 Axis in Macrophages

BACKGROUND

S-Nitrosylation (SNO), a prototypic redox-based posttranslational modification, is involved in cardiovascular disease. Aortic aneurysm and dissection are high-risk cardiovascular diseases without an effective cure. The aim of this study was to determine the role of SNO of Septin2 in macrophages in aortic aneurysm and dissection.

METHODS

Biotin-switch assay combined with liquid chromatography-tandem mass spectrometry was performed to identify the S-nitrosylated proteins in aortic tissue from both patients undergoing surgery for aortic dissection and Apoe-/- mice infused with angiotensin II. Angiotensin II-induced aortic aneurysm model and β-aminopropionitrile-induced aortic aneurysm and dissection model were used to determine the role of SNO of Septin2 (SNO-Septin2) in aortic aneurysm and dissection development. RNA-sequencing analysis was performed to recapitulate possible changes in the transcriptome profile of SNO-Septin2 in macrophages in aortic aneurysm and dissection. Liquid chromatography-tandem mass spectrometry and coimmunoprecipitation were used to uncover the TIAM1-RAC1 (Ras-related C3 botulinum toxin substrate 1) axis as the downstream target of SNO-Septin2. Both R-Ketorolac and NSC23766 treatments were used to inhibit the TIAM1-RAC1 axis.

RESULTS

Septin2 was identified S-nitrosylated at cysteine 111 (Cys111) in both aortic tissue from patients undergoing surgery for aortic dissection and Apoe-/- mice infused with Angiotensin II. SNO-Septin2 was demonstrated driving the development of aortic aneurysm and dissection. By RNA-sequencing, SNO-Septin2 in macrophages was demonstrated to exacerbate vascular inflammation and extracellular matrix degradation in aortic aneurysm. Next, TIAM1 (T lymphoma invasion and metastasis-inducing protein 1) was identified as a SNO-Septin2 target protein. Mechanistically, compared with unmodified Septin2, SNO-Septin2 reduced its interaction with TIAM1 and activated the TIAM1-RAC1 axis and consequent nuclear factor-κB signaling pathway, resulting in stronger inflammation and extracellular matrix degradation mediated by macrophages. Consistently, both R-Ketorolac and NSC23766 treatments protected against aortic aneurysm and dissection by inhibiting the TIAM1-RAC1 axis.

CONCLUSIONS

SNO-Septin2 drives aortic aneurysm and dissection through coupling the TIAM1-RAC1 axis in macrophages and activating the nuclear factor-κB signaling pathway-dependent inflammation and extracellular matrix degradation. Pharmacological blockade of RAC1 by R-Ketorolac or NSC23766 may therefore represent a potential treatment against aortic aneurysm and dissection.

miR-590-5p/Tiam1-mediated glucose metabolism promotes malignant evolution of pancreatic cancer by regulating SLC2A3 stability

BACKGROUND

T lymphoma invasion and metastasis 1 (Tiam1) is a tumor related gene that specifically activates Rho-like GTPases Rac1 and plays a critical role in the progression of various malignancies. Glycolysis plays an important role in cancer progression, it is crucial for supplying energy and producing metabolic end products, which can maintain the survival of tumor cells. As yet, however, the mechanism of Tiam1 in glycolysis reprogramming of pancreatic cancer (PC) remains to be clarified. Here, we investigated the functional role of Tiam1 in PC cell proliferation, metastasis and glycolysis reprogramming. It is expected to provide a new direction for clinical treatment.

METHODS

The clinical relevance of Tiam1 was evaluated in 66 patients with PC, the effect of Tiam1 on cell proliferation was detected via 5-Ethynyl-2'-deoxyuridine (EdU) and colony formation. The ability of cell migration was detected by the wound healing and Transwell. Quantitative real time polymerase chain reaction (qRT-PCR) and luciferase reporter gene experiments clarify the regulatory relationship of miR-590-5p inhibiting Tiam1. Detection of the molecular mechanism of Tiam1 regulating glucose metabolism reprogramming in PC by glucose metabolism kit. RNA sequencing and Co-Immunoprecipitation (CoIP) have identified glucose transporter protein 3 (SLC2A3) as a key downstream target gene for miR-590-5p/Tiam1.

RESULTS

We found that Tiam1 expression increased in PC tissues and was associated with lymph node metastasis. The silencing or exogenous overexpression of Tiam1 significantly altered the proliferation, invasion, and angiogenesis of PC cells through glucose metabolism pathway. In addition, Tiam1 could interact with the crucial SLC2A3 and promote the evolution of PC in a SLC2A3-dependent manner. Moreover, miR-590-5p was found to exacerbate the PC cell proliferation, migration and invasion by targeting Tiam1. Furthermore, the reversing effects on proliferation, migration and invasion were found in PC cells with miR-590-5p/Tiam1 overexpression after applying glucose metabolism inhibition.

CONCLUSIONS

Our findings demonstrate the critical role of Tiam1 in PC development and the miR-590-5p/Tiam1/SLC2A3 signaling pathway may serve as a target for new PC therapeutic strategies.

Genetic parameters estimation and genome molecular marker identification for gestation length in pigs

Gestation length (GL) plays an important role in piglet maturation of major organs and development of body, while the genetic molecular markers of GL have not been extensively identified. In this study, according to the 5,662 effective records of 3,072 sows, the heritability and repeatability of GL were estimated through the dmuai of DMU Version 6.5.1 with a repeatability model, namely, h 2 = 0.1594 and r e 2 = 0.2437. Among these sows, 906 individuals were genotyped with the GeneSeek Genomic Profiler (GGP) Porcine 50K Chip and imputed to the genome-wide level (9,212,179 SNPs) by the online software PHARP v1 for subsequent quality control and GWAS analyses. Further, the Fst was also performed to measure whether the actual frequency of genotypes in different GL phenotypes deviated from the theoretical proportion of genetic balance. We observed the highest degree of differentiation (average Fst value = 0.0376) in the group of 114 and 118 days, and identified a total of 1,002 SNPs strongly associated with GL. Through screening the genes located within a 500 kb distance on either side of the significant SNPs, we proposed 4,588 candidate genes. By the functional annotation, these candidates were found to be mainly involved in multicellular organism metabolism, early endosome, embryo implantation and development, and body and organ signaling pathway. Because of the simultaneous confirmation by GWAS and Fst analyses, there were 20 genes replied to be the most promising candidates including HUNK, ARHGDIB, ERP27, RERG, NEDD9, TMEM170B, SCAF4, SOD1, TIAM1, ENSSSCG00000048838, ENSSSCG00000047227, EDN1, HIVEP1, ENSSSCG00000043944, LRATD1, ENSSSCG00000048577, ENSSSCG00000042932, ENSSSCG00000041405, ENSSSCG00000045589, and ADTRP. This study provided effective molecular information for the genetic improvement of GL in pigs.

Zkscan3 affects erythroblast development by regulating the transcriptional activity of GATA1 and KLF1 in mice

ZKSCAN3 encodes a zinc-finger transcription factor that regulates the expression of important genes and plays a significant role in tumor development, pathogenesis, and metastasis. However, its biological functions under normal physiological conditions remain largely unknown. In our previous studies, using flow cytometry, we found that the deletion of Zkscan3 may cause abnormal erythropoiesis. In this study, we found that, in a Zkscan3 knockout mice model, the number of splenic early-stage (basophilic-erythroblasts) and late-stage (chromatophilic-erythroblasts to polychromatophilic-erythroblasts through orthochromatophilic-erythroblasts) erythroblasts increased, whereas the number of late erythroblasts in the bone marrow decreased. Moreover, the phenotype was exacerbated after treating mice with phenylhydrazine (PHZ), which causes severe hemolytic anemia. In the knockout mice treated with PHZ, the percentage of reticulocyte in the peripheral blood conspicuously increased, whereas MCHC and red blood cells decreased. Then, we performed RNA-seq and quantitative-polymerase chain reaction assay and found that the expression of GATA1 and Tiam1 in erythroblasts were upregulated, whereas KLF1 was downregulated. Luciferase assays showed that Zkscan3 inhibited the transcription of GATA1 and Tiam1 and promoted the expression of KLF1. Additionally, ChIP and CO-IP results confirmed that Zkscan3 directly interacts with GATA1 and inhibits its transcriptional activity in MEL cells. Our results demonstrate, for the first time, the significant role of Zkscan3 in physiological erythropoiesis through the interaction with GATA1, both at the DNA and protein level, and with Tiam1 and KLF1 at the DNA level.

Mycotoxin deoxynivalenol affects myoblast differentiation via downregulating cytoskeleton and ECM-integrin-FAK-RAC-PAK signaling pathway

As a common mycotoxin, deoxynivalenol (DON) contaminates cereal grains and feed in field or during processing and storage. DON elicits a spectrum of adverse effects in animals including anorexia and growth retardation. Especially, the presence of DON has also been detected in muscle, suggesting that DON may has the potential to affect the development of muscle. However, the relevant research is very rare and the molecular mechanism remains unclear. Myoblasts differentiation into multinucleated myotubes is one of the crucial steps of skeletal muscle development. In the present study, we investigated the effects of DON on differentiation of myoblasts using murine C2C12 cells model. The results indicated that DON dose-dependent inhibited the formation of myotubes in C2C12 cells. After performing omics techniques, a total of 149 differentially expressed genes were identified. The expression of cytoskeleton proteins and extracellular matrix (ECM) proteins were downregulated by DON. Furthermore, DON significantly downregulated the expression of integrin αv and integrin β5, leading to inhibition of the ECM-integrin receptor interaction. The focal adhesion kinase (FAK) and phosphorylated forms, ras-related C3 botulinum toxin substrate (RAC) and p21-activated kinases 1 (PAK1) were also downregulated by DON. Taken together, our findings suggest that DON has the potent to affect the differentiation of myoblasts via downregulating of cytoskeleton and ECM-integrin-FAK-RAC-PAK signaling pathway.

Rho GTPases in Skeletal Muscle Development and Homeostasis

Rho guanosine triphosphate hydrolases (GTPases) are molecular switches that cycle between an inactive guanosine diphosphate (GDP)-bound and an active guanosine triphosphate (GTP)-bound state during signal transduction. As such, they regulate a wide range of both cellular and physiological processes. In this review, we will summarize recent work on the role of Rho GTPase-regulated pathways in skeletal muscle development, regeneration, tissue mass homeostatic balance, and metabolism. In addition, we will present current evidence that links the dysregulation of these GTPases with diseases caused by skeletal muscle dysfunction. Overall, this information underscores the critical role of a number of members of the Rho GTPase subfamily in muscle development and the overall metabolic balance of mammalian species.

Targeting Small GTPases and Their Prenylation in Diabetes Mellitus

A fundamental role of pancreatic β-cells to maintain proper blood glucose level is controlled by the Ras superfamily of small GTPases that undergo post-translational modifications, including prenylation. This covalent attachment with either a farnesyl or a geranylgeranyl group controls their localization, activity, and protein–protein interactions. Small GTPases are critical in maintaining glucose homeostasis acting in the pancreas and metabolically active tissues such as skeletal muscles, liver, or adipocytes. Hyperglycemia-induced upregulation of small GTPases suggests that inhibition of these pathways deserves to be considered as a potential therapeutic approach in treating T2D. This Perspective presents how inhibition of various points in the mevalonate pathway might affect protein prenylation and functioning of diabetes-affected tissues and contribute to chronic inflammation involved in diabetes mellitus (T2D) development. We also demonstrate the currently available molecular tools to decipher the mechanisms linking the mevalonate pathway’s enzymes and GTPases with diabetes.

Rho Family GTPases and Rho GEFs in Glucose Homeostasis

Dysregulation of glucose homeostasis leading to metabolic syndrome and type 2 diabetes is the cause of an increasing world health crisis. New intriguing roles have emerged for Rho family GTPases and their Rho guanine nucleotide exchange factor (GEF) activators in the regulation of glucose homeostasis. This review summates the current knowledge, focusing in particular on the roles of Rho GEFs in the processes of glucose-stimulated insulin secretion by pancreatic β cells and insulin-stimulated glucose uptake into skeletal muscle and adipose tissues. We discuss the ten Rho GEFs that are known so far to regulate glucose homeostasis, nine of which are in mammals, and one is in yeast. Among the mammalian Rho GEFs, P-Rex1, Vav2, Vav3, Tiam1, Kalirin and Plekhg4 were shown to mediate the insulin-stimulated translocation of the glucose transporter GLUT4 to the plasma membrane and/or insulin-stimulated glucose uptake in skeletal muscle or adipose tissue. The Rho GEFs P-Rex1, Vav2, Tiam1 and β-PIX were found to control the glucose-stimulated release of insulin by pancreatic β cells. In vivo studies demonstrated the involvement of the Rho GEFs P-Rex2, Vav2, Vav3 and PDZ-RhoGEF in glucose tolerance and/or insulin sensitivity, with deletion of these GEFs either contributing to the development of metabolic syndrome or protecting from it. This research is in its infancy. Considering that over 80 Rho GEFs exist, it is likely that future research will identify more roles for Rho GEFs in glucose homeostasis.