scholarly journals N-cadherin signaling via Trio assembles adherens junctions to restrict endothelial permeability

2018 ◽  
Vol 218 (1) ◽  
pp. 299-316 ◽  
Author(s):  
Kevin Kruse ◽  
Quinn S. Lee ◽  
Ying Sun ◽  
Jeff Klomp ◽  
Xiaoyan Yang ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Intracellular Signaling ◽  
Adherens Junctions ◽  
Endothelial Permeability ◽  
Endothelial Barrier ◽  
Vascular Endothelial ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Rhoa Signaling

Vascular endothelial (VE)–cadherin forms homotypic adherens junctions (AJs) in the endothelium, whereas N-cadherin forms heterotypic adhesion between endothelial cells and surrounding vascular smooth muscle cells and pericytes. Here we addressed the question whether both cadherin adhesion complexes communicate through intracellular signaling and contribute to the integrity of the endothelial barrier. We demonstrated that deletion of N-cadherin (Cdh2) in either endothelial cells or pericytes increases junctional endothelial permeability in lung and brain secondary to reduced accumulation of VE-cadherin at AJs. N-cadherin functions by increasing the rate of VE-cadherin recruitment to AJs and induces the assembly of VE-cadherin junctions. We identified the dual Rac1/RhoA Rho guanine nucleotide exchange factor (GEF) Trio as a critical component of the N-cadherin adhesion complex, which activates both Rac1 and RhoA signaling pathways at AJs. Trio GEF1-mediated Rac1 activation induces the recruitment of VE-cadherin to AJs, whereas Trio GEF2-mediated RhoA activation increases intracellular tension and reinforces Rac1 activation to promote assembly of VE-cadherin junctions and thereby establish the characteristic restrictive endothelial barrier.

Microtubules-associated Rac regulation of endothelial barrier: a role of Asef in acute lung injury

2017 ◽  
Vol 65 (8) ◽  
pp. 1089-1092 ◽  
Author(s):  
Pratap Karki ◽  
Anna A Birukova
Keyword(s):  
Critical Role ◽  
Endothelial Permeability ◽  
Small Gtpase ◽  
Endothelial Barrier ◽  
Protective Effects ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Lung Injuries

The endothelial barrier function regulated by the cytoskeletal reorganizations has been implicated in the pathogenesis of multiple lung diseases including asthma, sepsis, edema, and acute respiratory distress syndrome. The extensive studies have established that activation of small GTPase Rac is a key mechanism in endothelial barrier protection but the role of microtubules-associated Rac in the endothelial functions remains poorly understood. With the emerging evidences that microtubules disassembly also plays a critical role in actin cytoskeleton remodeling leading to endothelial permeability, the knowledge on microtubules-mediated regulation of endothelial barrier is imperative to better understand the etiology of lung injuries as well as to develop novel therapeutics against these disorders. In this regard, our recent studies have revealed some novel aspects of microtubules-mediated regulation of endothelial barrier functions and unraveled a putative role of Rac-specific guanine nucleotide exchange factor Asef in mediating the barrier protective effects of hepatocyte growth factor. In this review, we will discuss the role of this novel Rac activator Asef in endothelial barrier protection and its regulation by microtubules.

The Leukemia-Associated Rho Guanine Nucleotide Exchange Factor (LARG) Is Essential for Survival and Proliferation of AML1-ETO Associated AML Cells

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 923-923
Author(s):  
Shuhong Shen ◽  
Yi Zheng ◽  
James C. Mulloy
Keyword(s):  
Cell Cycle ◽  
Cell Lines ◽  
Fusion Gene ◽  
Guanine Nucleotide Exchange Factor ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Rhoa Signaling

Abstract Abstract 923 AML1-ETO (AE), the product of translocation 8;21, is the most frequently observed fusion gene in acute myeloid leukemia (AML). Although AE is not sufficient to induce leukemia by itself, it endows a significant survival and growth advantage to hematopoietic progenitors. In a search of various AML microarray databases, we found that the Leukemia-Associated Rho Guanine nucleotide exchange factor (LARG) gene expression is consistently upregulated in samples from AE-positive AML patients compared to other types of AML. This observation was confirmed in an independent cohort of AML samples by qPCR and Western Blot analysis, and in a pre-leukemia cell model generated by AE expression in CD34+ human cord blood (CB) cells compared with CB cells transduced with the MLL-AF9 (MA9) fusion gene or control retroviral vector. ChIP-PCR assays further indicate that AE directly binds to the LARG regulatory region through cis-elements containing AML1 (Runx1) binding sites. LARG, a RhoA GEF, can activate the RhoA pathway which is important for interaction between cells and their environment. We found that the AE cell lines were more adhesive to fibronectin than the MA9 cell lines. When we used lentiviral vectors expressing shRNA to suppress LARG expression in AE+ pre-leukemic cells, the cells showed a significant decrease in adhesion to fibronectin. In addition, knockdown of LARG also significantly interfered with the growth of AE cells in that the shRNA transduced cells displayed a competitive disadvantage relative to non-transduced or control-transduced cells in a proliferation assay. Cell cycle analysis revealed that LARG knockdown induced cell cycle exit, while Annexin V staining showed that LARG suppression promoted apoptosis of AE cells. Because LARG is a well-known guanine nucleotide exchange factor (GEF) for RhoA GTPase, we examined the downstream signaling events of the LARG/Rho axis, including phosphorylation of MLC and AURORA, targets of Rho-associated protein kinase (ROCK). pMLC and pAURORA were significantly down-regulated upon knockdown of LARG. Phosphorylation of Stat3, another protein downstream of RhoA signaling important for the proliferation and survival of myeloid cells, was also decreased upon LARG knockdown. These findings suggest that LARG is a transcriptional target of the AML1-ETO fusion protein and the LARG-RhoA signaling pathway plays an essential role in the proliferation and survival of AE cells. The LARG/RhoA pathway may serve as a new therapeutic target in t(8;21) AML. Disclosures: No relevant conflicts of interest to declare.

scholarly journals The Rho/Rac guanine nucleotide exchange factor Vav1 regulates HIF-1α and GLUT-1 expression and glucose uptake in the brain

2019 ◽  
Author(s):  
Jaewoo Hong ◽  
Yurim Kim ◽  
Sudhirkumar Yanpallewar ◽  
P. Charles Lin
Keyword(s):  
Endothelial Cells ◽  
Glucose Uptake ◽  
Guanine Nucleotide Exchange Factor ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Glut 1 ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
The Brain

AbstractVav1 is a Rho/Rac guanine nucleotide exchange factor expressed in hematopoietic and endothelial cells that are involved in a wide range of cellular functions. It is also stabilized under hypoxic conditions when it regulates the accumulation of the transcription factor HIF-1α, which activates the transcription of target genes to orchestrate a cellular response to low oxygen. One of the genes induced by HIF-1α is GLUT-1, which is the major glucose transporter expressed in vessels that supply energy to the brain. Here, we identify a role for Vav1 in providing glucose to the brain. We found that Vav1 deficiency downregulates HIF-1α and GLUT-1 levels in endothelial cells, including blood-brain barrier cells. This downregulation of GLUT-1, in turn, reduced glucose uptake to endothelial cells both in vitro and in vivo, and reduced glucose levels in the brain.Furthermore, endothelial cell-specific Vav1 knock-out in mice, which caused glucose uptake deficiency, also led to a learning delay in fear conditioning experiments. Our results suggest that Vav1 promotes learning by activating HIF-1α and GLUT-1 and thereby distributing glucose to the brain. They further demonstrate the importance of glucose transport by endothelial cells in brain functioning and reveal a potential new axis for targeting GLUT-1 deficiency syndromes and other related brain diseases.

scholarly journals Impact of Atherosclerosis- and Diabetes-Related Dicarbonyls on Vascular Endothelial Permeability: A Comparative Assessment

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Mikhail V. Samsonov ◽  
Asker Y. Khapchaev ◽  
Alexander V. Vorotnikov ◽  
Tatyana N. Vlasik ◽  
Elena V. Yanushevskaya ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Fluorescent Microscopy ◽  
Endothelial Permeability ◽  
Time Lapse ◽  
Protein Band ◽  
Endothelial Barrier ◽  
Vascular Endothelial ◽  
Barrier Dysfunction ◽  
Cytoskeletal Organization ◽  
Diabetes Patients

Background. Malondialdehyde (MDA), glyoxal (GO), and methylglyoxal (MGO) levels increase in atherosclerosis and diabetes patients. Recent reports demonstrate that GO and MGO cause vascular endothelial barrier dysfunction whereas no evidence is available for MDA. Methods. To compare the effects of MDA, GO, or MGO on endothelial permeability, we used human EA.hy926 endothelial cells as a standard model. To study cortical cytoplasm motility and cytoskeletal organization in endothelial cells, we utilized time-lapse microscopy and fluorescent microscopy. To compare dicarbonyl-modified protein band profiles in these cells, we applied Western blotting with antibodies against MDA- or MGO-labelled proteins. Results. MDA (150–250 μM) irreversibly suppressed the endothelial cell barrier, reduced lamellipodial activity, and prevented intercellular contact formation. The motile deficiency of MDA-challenged cells was accompanied by alterations in microtubule and microfilament organization. These detrimental effects were not observed after GO or MGO (250 μM) administration regardless of confirmed modification of cellular proteins by MGO. Conclusions. Our comparative study demonstrates that MDA is more damaging to the endothelial barrier than GO or MGO. Considering that MDA endogenous levels exceed those of GO or MGO and tend to increase further during lipoperoxidation, it appears important to reduce oxidative stress and, in particular, MDA levels in order to prevent sustained vascular hyperpermeability in atherosclerosis and diabetes patients.

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