Receptor Tyrosine Kinases Activate Canonical WNT/β-Catenin Signaling via MAP Kinase/LRP6 Pathway and Direct β-Catenin Phosphorylation

Receptor tyrosine kinase signaling cooperates with WNT/β-catenin signaling in regulating many biological processes, but the mechanisms of their interaction remain poorly defined. We describe a potent activation of WNT/β-catenin by FGFR2, FGFR3, EGFR and TRKA kinases, which is independent of the PI3K/AKT pathway. Instead, this phenotype depends on ERK MAP kinase-mediated phosphorylation of WNT co-receptor LRP6 at Ser1490 and Thr1572 during its Golgi network-based maturation process. This phosphorylation dramatically increases the cellular response to WNT. Moreover, FGFR2, FGFR3, EGFR and TRKA directly phosphorylate β-catenin at Tyr142, which is known to increase cytoplasmic β-catenin concentration via release of β-catenin from membranous cadherin complexes. We conclude that signaling via ERK/LRP6 pathway and direct β-catenin phosphorylation at Tyr142 represent two mechanisms used by various receptor tyrosine kinase systems to activate canonical WNT signaling

Viral delivery of tissue nonspecific alkaline phosphatase diminishes craniosynostosis in one of two FGFR2C342Y/+ mouse models of Crouzon syndrome.

Craniosynostosis is the premature fusion of cranial bones. The goal of this study was to determine if delivery of recombinant tissue nonspecific alkaline phosphatase (TNAP) could prevent or diminish the severity of craniosynostosis in a C57BL/6 FGFR2C342Y/+ model of neonatal onset craniosynostosis or a BALB/c FGFR2C342Y/+ model of postnatal onset craniosynostosis. Mice were injected with a lentivirus encoding a mineral targeted form of TNAP immediately after birth. Cranial bone fusion as well as cranial bone volume, mineral content and density were assessed by micro CT. Craniofacial shape was measured with calipers. Alkaline phosphatase, alanine amino transferase (ALT) and aspartate amino transferase (AST) activity levels were measured in serum. Neonatal delivery of TNAP diminished craniosynostosis severity from 94% suture obliteration in vehicle treated mice to 67% suture obliteration in treated mice, p<0.02) and the incidence of malocclusion from 82.4% to 34.7% (p<0.03), with no effect on cranial bone in C57BL/6 FGFR2C342Y/+ mice. In contrast, treatment with TNAP increased cranial bone volume (p< 0.01), density (p< 0.01) and mineral content (p< 0.01) as compared to vehicle treated controls, but had no effect on craniosynostosis or malocclusion in BALB/c FGFR2C342Y/+ mice. These results indicate that postnatal recombinant TNAP enzyme therapy diminishes craniosynostosis severity in the C57BL/6 FGFR2C342Y/+ neonatal onset mouse model of Crouzon syndrome, and that effects of exogenous TNAP are genetic background dependent

FACTORS ASSOCIATED WITH ESTIMATE OF HIGH TERATOGENIC RISK IN FEMALES EXPOSED TO ANTI-INFECTIVE AND ANTI-INFLAMMATORY DRUGS DURING PREGNANCY

ABSTRACT Introduction. Considering that small number of drugs are completely safe for use during pregnancy, right choice and adequate risk assessment is extremely important. Objective. The aim of this study was to analyze factors associated with estimate of high teratogenic risk (as judged by clinical pharmacologist) in pregnant females who were prescribed anti-infective drugs or mild analgesics. Methods. A cross-sectional study included 284 pregnant women who came for an advice about teratogenic risk to clinical pharmacologist in Clinical Centre Kragujevac, Serbia during the period from 1997 to 2012. All of included pregnant women were prescribed mild analgesics and/or anti-infective drugs during the first 3 months of pregnancy. The data were collected from patient files and by phone interviews. Results. Clinical pharmacologists estimated the risk of teratogenicity as “high” in pregnant females who were using tetracyclines or propionic acid derivatives. Disorders of development reported by mothers during phone interviews were associated with cephalosporin use during first 3 months of pregnancy, while miscarriages or abortions happened more often in women who used a tetracycline. Conclusions. Estimate of risk from congenital anomalies after use of drugs during pregnancy, which make clinical pharmacologists as part of their routine healthcare services, depends on amount of published data about previous experiences with specific drugs during the first 3 months of pregnancy. Key Words: pregnancy; drugs; risk of teratogenicity; risk estimat

Receptor Tyrosine Kinases Activate Canonical WNT/?-Catenin Signaling via MAP Kinase/LRP6 Pathway and Direct Beta-Catenin Phosphorylation

Receptor tyrosine kinase signaling cooperates with WNT/β-catenin signaling in regulating many biological processes, but the mechanisms of their interaction remain poorly defined. We describe a potent activation of WNT/β-catenin by FGFR2, FGFR3, EGFR and TRKA kinases, which is independent of the PI3K/AKT pathway. Instead, this phenotype depends on ERK MAP kinase-mediated phosphorylation of WNT co-receptor LRP6 at Ser1490 and Thr1572 during its Golgi network-based maturation process. This phosphorylation dramatically increases the cellular response to WNT. Moreover, FGFR2, FGFR3, EGFR and TRKA directly phosphorylate β-catenin at Tyr142, which is known to increase cytoplasmic β-catenin concentration via release of β-catenin from membranous cadherin complexes. We conclude that signaling via ERK/LRP6 pathway and direct β-catenin phosphorylation at Tyr142 represent two mechanisms used by various receptor tyrosine kinase systems to activate canonical WNT signaling

Receptor Tyrosine Kinases Activate Canonical WNT/?-Catenin Signaling via MAP Kinase/LRP6 Pathway and Direct Beta-Catenin Phosphorylation

Receptor tyrosine kinase signaling cooperates with WNT/β-catenin signaling in regulating many biological processes, but the mechanisms of their interaction remain poorly defined. We describe a potent activation of WNT/β-catenin by FGFR2, FGFR3, EGFR and TRKA kinases, which is independent of the PI3K/AKT pathway. Instead, this phenotype depends on ERK MAP kinase-mediated phosphorylation of WNT co-receptor LRP6 at Ser1490 and Thr1572 during its Golgi network-based maturation process. This phosphorylation dramatically increases the cellular response to WNT. Moreover, FGFR2, FGFR3, EGFR and TRKA directly phosphorylate β-catenin at Tyr142, which is known to increase cytoplasmic β-catenin concentration via release of β-catenin from membranous cadherin complexes. We conclude that signaling via ERK/LRP6 pathway and direct β-catenin phosphorylation at Tyr142 represent two mechanisms used by various receptor tyrosine kinase systems to activate canonical WNT signaling

RTKs phosphorylate β-catenin at Tyr142.

<p>(A) RCS cells were treated for indicated times with FGF2 (10 ng/ml) in the presence of heparin (1 µg/ml), and analyzed for β-catenin phosphorylation at Tyr142 by WB (arrow). (B) HEK293 cells were transfected with wt FGFR2 or its activating mutant Y375C, and analyzed for indicated molecules 48 hours later. Note the increased β-catenin phosphorylation at Tyr142 (arrow). (C) Active recombinant FGFR3, FGFR2, TRKA and EGFR were subjected to a cell-free kinase assay with recombinant β-catenin as a substrate. Samples with ATP or kinase omitted serve as controls for kinase reaction.</p

Disease-associated FGFR3 and FGFR2 mutants signal via ERK/LRP6 pathway.

<p>(A) RCS cells were transfected with wt FGFR3 or activating FGFR3 mutants (N540K, G380R, R248C, Y373C, K650M, K650E), and analyzed for the indicated molecules by WB 48 hours later. The levels of ERK phosphorylation vary among the tested mutants, reflecting the different strength of FGFR3 activation by each particular mutation <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035826#pone.0035826-Krejci2" target="_blank">[24]</a>. K508M - kinase inactive FGFR3 mutant. GFP and empty vectors serve as transfection controls. (B) LRP6 phosphorylation at Thr1572 caused by highly activating FGFR3 mutants R248C and K650E. (C) Cells were transfected with the indicated FGFR3 vectors together with Topflash reporter vectors, treated with WNT3a and analyzed for luciferase activity. Data represent an average from three transfections (each measured twice), with the indicated standard deviations. A logarithmic scale of the <i>y</i>-axis is necessary to express the massive Topflash activation in WNT3a-treated cells expressing activating FGFR3 mutants (* <i>p</i><0.001; Student’s <i>t</i>-test; compared to wt FGFR3). Results are representative of four experiments. (D) Cells were transfected with wt FGFR2 or activating FGFR2 mutants (S252W, P253R, C342R, C342Y, Y375C), and analyzed for the indicated molecules by WB. Note the significant ERK and LRP6 phosphorylation caused by C342R, C342Y and Y375C mutants, which correlates with increased basal (E; upper graph) and WNT3a-induced (E; lower graph) β-catenin activity, evidenced by Topflash experiment. Results are representative for three experiments (* <i>p</i><0.001; Student’s <i>t</i>-test; compared to wt FGFR2).</p