The receptor tyrosine kinase EphB4 and ephrin-B ligands restrict angiogenic growth of embryonic veins in Xenopus laevis

Development ◽  
2000 ◽  
Vol 127 (2) ◽  
pp. 269-278 ◽  
Author(s):  
P.M. Helbling ◽  
D.M. Saulnier ◽  
A.W. Brandli
Keyword(s):  
Xenopus Laevis ◽  
Tyrosine Kinases ◽  
Dominant Negative ◽  
Receptor Expression ◽  
Signaling Systems ◽  
Xenopus Embryos ◽  
Ephb Receptor ◽  
Ephb Receptors ◽  
Vessel Development ◽  
Neural Crest Migration

The cues and signaling systems that guide the formation of embryonic blood vessels in tissues and organs are poorly understood. Members of the Eph family of receptor tyrosine kinases and their cell membrane-anchored ligands, the ephrins, have been assigned important roles in the control of cell migration during embryogenesis, particularly in axon guidance and neural crest migration. Here we investigated the role of EphB receptors and their ligands during embryonic blood vessel development in Xenopus laevis. In a survey of tadpole-stage Xenopus embryos for EphB receptor expression, we detected expression of EphB4 receptors in the posterior cardinal veins and their derivatives, the intersomitic veins. Vascular expression of other EphB receptors, including EphB1, EphB2 or EphB3, could however not be observed, suggesting that EphB4 is the principal EphB receptor of the early embryonic vasculature of Xenopus. Furthermore, we found that ephrin-B ligands are expressed complementary to EphB4 in the somites adjacent to the migratory pathways taken by intersomitic veins during angiogenic growth. We performed RNA injection experiments to study the function of EphB4 and its ligands in intersomitic vein development. Disruption of EphB4 signaling by dominant negative EphB4 receptors or misexpression of ephrin-B ligands in Xenopus embryos resulted in intersomitic veins growing abnormally into the adjacent somitic tissue. Our findings demonstrate that EphB4 and B-class ephrins act as regulators of angiogenesis possibly by mediating repulsive guidance cues to migrating endothelial cells.

Cell transformation by fibroblast growth factors can be suppressed by truncated fibroblast growth factor receptors

1994 ◽  
Vol 14 (11) ◽  
pp. 7660-7669
Author(s):  
Y Li ◽  
C Basilico ◽  
A Mansukhani
Keyword(s):  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Tyrosine Kinases ◽  
Dominant Negative ◽  
Receptor Expression ◽  
Scatchard Analysis ◽  
Fibroblast Growth ◽  
Fibroblast Growth Factor Receptors ◽  
Truncated Receptor ◽  
Nih 3T3

Ligand-induced dimerization and transphosphorylation are thought to be important events by which receptor tyrosine kinases generate cellular signals. We have investigated the ability of signalling-defective, truncated fibroblast growth factor (FGF) receptors (FGFR-1 and FGFR-2) to block the FGF response in cells that express both types of endogenous FGF receptors. When these dominant negative receptors are expressed in NIH 3T3 cells transformed by the secreted FGF-4, the transformed properties of the cells can be reverted to various degrees, with better reversion phenotype correlating with higher levels of truncated receptor expression. Furthermore, truncated FGFR-2 is significantly more efficient at producing reversion than FGFR-1, indicating that FGF-4 preferentially utilizes the FGFR-2 signalling pathway. NIH 3T3 clones expressing these truncated receptors are more resistant to FGF-induced mitogenesis and also exhibit reduced tyrosine phosphorylation upon treatment with FGF. The block in FGF-signalling, however, can be overcome by the addition of excess growth factor. The truncated receptors have binding affinities that are four- to eightfold lower than those of wild-type receptors, as measured by Scatchard analysis. We also observed a partial specificity in the responses of truncated-receptor-expressing clones to FGF-2 or FGF-4. Our results suggest that the block to signal transduction produced by kinase-negative FGF receptors is achieved through a combination of dominant negative effects and competition for growth factor binding with functional receptors.

scholarly journals Cell transformation by fibroblast growth factors can be suppressed by truncated fibroblast growth factor receptors.

1994 ◽  
Vol 14 (11) ◽  
pp. 7660-7669 ◽  
Author(s):  
Y Li ◽  
C Basilico ◽  
A Mansukhani
Keyword(s):  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Tyrosine Kinases ◽  
Dominant Negative ◽  
Receptor Expression ◽  
Scatchard Analysis ◽  
Fibroblast Growth ◽  
Fibroblast Growth Factor Receptors ◽  
Truncated Receptor ◽  
Nih 3T3

Ligand-induced dimerization and transphosphorylation are thought to be important events by which receptor tyrosine kinases generate cellular signals. We have investigated the ability of signalling-defective, truncated fibroblast growth factor (FGF) receptors (FGFR-1 and FGFR-2) to block the FGF response in cells that express both types of endogenous FGF receptors. When these dominant negative receptors are expressed in NIH 3T3 cells transformed by the secreted FGF-4, the transformed properties of the cells can be reverted to various degrees, with better reversion phenotype correlating with higher levels of truncated receptor expression. Furthermore, truncated FGFR-2 is significantly more efficient at producing reversion than FGFR-1, indicating that FGF-4 preferentially utilizes the FGFR-2 signalling pathway. NIH 3T3 clones expressing these truncated receptors are more resistant to FGF-induced mitogenesis and also exhibit reduced tyrosine phosphorylation upon treatment with FGF. The block in FGF-signalling, however, can be overcome by the addition of excess growth factor. The truncated receptors have binding affinities that are four- to eightfold lower than those of wild-type receptors, as measured by Scatchard analysis. We also observed a partial specificity in the responses of truncated-receptor-expressing clones to FGF-2 or FGF-4. Our results suggest that the block to signal transduction produced by kinase-negative FGF receptors is achieved through a combination of dominant negative effects and competition for growth factor binding with functional receptors.

scholarly journals Graded and Lamina-Specific Distributions of Ligands of EphB Receptor Tyrosine Kinases in the Developing Retinotectal System

1997 ◽  
Vol 191 (1) ◽  
pp. 14-28 ◽  
Author(s):  
Janet E. Braisted ◽  
Todd McLaughlin ◽  
Hai U. Wang ◽  
Glenn C. Friedman ◽  
David J. Anderson ◽  
...  
Keyword(s):  
Tyrosine Kinases ◽  
Receptor Tyrosine Kinases ◽  
Ephb Receptor ◽  
Retinotectal System

Expression of a dominant negative retinoic acid receptor ? in Xenopus embryos leads to partial resistance to retinoic acid

1994 ◽  
Vol 203 (5) ◽  
pp. 254-265 ◽  
Author(s):  
Darrin Paul Smith ◽  
Clive Scott Mason ◽  
Elizabeth Jones ◽  
Robert Old
Keyword(s):  
Retinoic Acid ◽  
Partial Resistance ◽  
Retinoic Acid Receptor ◽  
Dominant Negative ◽  
Acid Receptor ◽  
Xenopus Embryos

Transcriptional transactivation functions localized to the glucocorticoid receptor N terminus are necessary for steroid induction of lymphocyte apoptosis

1992 ◽  
Vol 12 (2) ◽  
pp. 589-597
Author(s):  
E S Dieken ◽  
R L Miesfeld
Keyword(s):  
Transcriptional Regulation ◽  
Glucocorticoid Receptor ◽  
Target Genes ◽  
Dominant Negative ◽  
Receptor Expression ◽  
Transactivation Domain ◽  
Lymphocyte Apoptosis ◽  
Murine Cell Line ◽  
N Terminus ◽  
Simplex Virus

Genetic studies have suggested that transcriptional regulation of specific target genes (by either induction or repression) is the molecular basis of glucocorticoid-mediated lymphocyte apoptosis. To examine the role of transcriptional regulation more directly, we developed a complementation assay utilizing stable transfection of wild-type (wt) and mutant (nti) glucocorticoid receptor (GR) cDNA constructs into a GR-deficient S49 murine cell line (7r). Our data confirm that the level of functional GR is rate limiting for S49 apoptosis and moreover that the GR amino terminus (N terminus), which as been deleted from the nti GR, is absolutely required for complementation in this system. Surprisingly, we found that at physiological levels of receptor, expression of the nti GR in cells containing wt GR results in enhanced dexamethasone sensitivity rather than a dominant negative phenotype. One interpretation of these data is that DNA binding by wt-nti heterodimers may be functionally similar to that of wt-wt homodimers, indicating that GRE occupancy by at least one transactivation domain may be sufficient to induce the hormonal response. To determine whether acidic activating sequences such as those localized to the GR N terminus are important in the induction of lymphocyte apoptosis, we tested the activity of a chimeric receptor in which we replaced the entire GR N terminus with sequences from the herpes simplex virus VP16 protein. Our results demonstrate that 7r cells expressing VP-GR fusions are indeed steroid sensitive, strongly supporting the idea that S49 apoptosis is dependent on transcriptional regulation of specific genes which respond to acidic activating domains, implying that induction, rather than repression, may be the critical initiating event.

The origins of primitive blood in Xenopus: implications for axial patterning

Development ◽  
1999 ◽  
Vol 126 (3) ◽  
pp. 423-434 ◽  
Author(s):  
M.C. Lane ◽  
W.C. Smith
Keyword(s):  
Xenopus Laevis ◽  
Marginal Zone ◽  
Cell Stage ◽  
Axial Patterning ◽  
Xenopus Embryos ◽  
Spemann's Organizer ◽  
Dorsal Mesoderm

The marginal zone in Xenopus laevis is proposed to be patterned with dorsal mesoderm situated near the upper blastoporal lip and ventral mesoderm near the lower blastoporal lip. We determined the origins of the ventralmost mesoderm, primitive blood, and show it arises from all vegetal blastomeres at the 32-cell stage, including blastomere C1, a progenitor of Spemann's organizer. This demonstrates that cells located at the upper blastoporal lip become ventral mesoderm, not solely dorsal mesoderm as previously believed. Reassessment of extant fate maps shows dorsal mesoderm and dorsal endoderm descend from the animal region of the marginal zone, whereas ventral mesoderm descends from the vegetal region of the marginal zone, and ventral endoderm descends from cells located vegetal of the bottle cells. Thus, the orientation of the dorsal-ventral axis of the mesoderm and endoderm is rotated 90(degrees) from its current portrayal in fate maps. This reassessment leads us to propose revisions in the nomenclature of the marginal zone and the orientation of the axes in pre-gastrula Xenopus embryos.

scholarly journals Anlotinib Induced Apoptosis and Regulated the Chemosensitivity and Immune-Related Properties of Leukemia Stem Cells By Inhibiting JAK2-STAT3/5 Signaling

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 12-12
Author(s):  
Long Liu ◽  
Long Yue Jiang ◽  
Bing Xu
Keyword(s):  
Stem Cells ◽  
Tyrosine Kinase ◽  
Immune Evasion ◽  
Tyrosine Kinases ◽  
Receptor Expression ◽  
The Self ◽  
Leukemia Stem Cells ◽  
Self Renewal ◽  
Stat Signaling ◽  
Apoptotic Proteins

Acute myeloid leukemia (AML) is derived from small populations of leukemia stem cells (LSCs) characterized by the self-renewal and chemoresistant properties. Residual LSCs after chemotherapy remain as the critical barriers to cure. Clearance of LSCs might rationally lead to an improvement of clinical outcome. Recently studies showed that JAK/STAT signaling play an important role in the self-renewal of AML-LSCs due to increased growth factor (GF) receptor expression such as c-kit, FLT3, CD123 and altered GF signaling by activating tyrosine kinases. Therefore, targeting such tyrosine kinases might be a strategy to eliminate LSCs. Anlotinib displayed its anti-tumor activity in lung cancer by targeting tyrosine kinase of VEGFR, FGFR, PDGFR and c-kit. However, whether anlotinib could inhibit the GF receptor-related tyrosine kinase overactivation and its downstream JAK-STAT signaling, and subsequently kill LSCs or regulate LSCs biology remains largely unknown. To explore whether anlotinib could exert effective ani-LSCs activity, we treated LSC like cell lines (CD34+CD38-KG-1 and Kasumi-1) with anlotinib, and found anlotinib could effectively induce apoptosis of LSC-like cells in a dose- and time-dependent manner. Similar results were observed in primary CD34+CD38-AML LSCs; notably, anlotinib did not significantly kill normal CD34+ cells in vitro. Additionally, the anti-LSC activity of anlotinib was further confirmed in the xenograft mouse model by injection of Kasumi cells (LSC-like cell line) into irradiated female BALB/c nude mice. To determine whether anlotinib could inhibit the over activation of the GF receptor-related tyrosine kinase, we performed western blot at 12h after anlotinib treatment when LSC-like cells did not showed significant apoptosis. As a result, anlotinib inhibit c-kit phosphorylation and JAK2 activation. Intriguingly, unlike JAK2 inhibitors, anlotinib could not only the inhibit phosphorylation of STAT3 and STAT5 but also downregulate their expression. Chemoresistance and immune evasion were the key features of LSCs, JAK2-STAT3/5 signaling was reported to involved in chemoresistance by upregulating anti-apoptotic proteins such as Bcl-2 ,Mcl-1 and also involved in immune escape by inducing immune suppressive molecules such as PD-L1 ,TGF-β.Thus we evaluated Bcl-2 expression and found a significant decrease in LSC-likes cells after anlotinib treatment. Similarly, PD-L1 and TGF-β were also significantly downregulated after anlotinib treatment. In conclusion, anlotinib not only displayed the effective anti-LSCs activity but also might regulate the chemoresistance and immune evasion of LSC by downregulating the anti-apoptotic proteins and suppressive molecules such as PD-L1, TGF-β respectively. Consequently, anlotinib might has the potential to contribute to a deeper clearance of LSCs by combining with chemotherapy or immunotherapy. Disclosures No relevant conflicts of interest to declare.

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