scholarly journals The Sensitivity of Activated Cys Ret Mutants to Glial Cell Line-Derived Neurotrophic Factor Is Mandatory To Rescue Neuroectodermic Cells from Apoptosis

2001 ◽  
Vol 21 (20) ◽  
pp. 6719-6730 ◽  
Author(s):  
Baharia Mograbi ◽  
Renata Bocciardi ◽  
Isabelle Bourget ◽  
Thierry Juhel ◽  
Dariush Farahi-Far ◽  
...  
Keyword(s):  
Thyroid Carcinoma ◽  
Tyrosine Kinase ◽  
Glial Cell ◽  
Receptor Tyrosine Kinase ◽  
Neurotrophic Factor ◽  
Developmental Defect ◽  
Loss Of Function ◽  
Wild Type ◽  
Gain Of Function ◽  
Activating Mutations

ABSTRACT Hirschsprung's disease (HSCR), a frequent developmental defect of the enteric nervous system is due to loss-of-function mutations of RET, a receptor tyrosine kinase essential for the mediation of glial cell-derived neurotrophic factor (GDNF)-induced cell survival. Instead, gain-of-function Cys mutations (e.g., Cys609, Cys620, and Cys634) of the same gene are responsible for thyroid carcinoma (MEN2A/familial medullary thyroid carcinoma) by causing a covalent Ret dimerization, leading to ligand-independent activation of its tyrosine kinase. In this context, the association of Cys609- or Cys620-activating mutations with HSCR is still an unresolved paradox. To address this issue, we have compared these two mutants with the Cys634 Ret variant, which has never been associated with HSCR, for their ability to rescue neuroectodermic cells (SK-N-MC cells) from apoptosis. We show here that despite their constitutively activated kinase, the mere expression of these three mutants does not allow cell rescue. Instead, we demonstrate that like the wild-type Ret, the Cys634 Ret variant can trigger antiapoptotic pathways only in response to GDNF. In contrast, Cys609 or Cys620 mutations, which impair the terminal Ret glycosylation required for its insertion at the plasma membrane, abrogate GDNF-induced cell rescue. Taken together, these data support the idea that sensitivity to GDNF is the mandatory condition, even for constitutively activated Ret mutants, to rescue neuroectodermic cells from apoptosis. These findings may help clarify how a gain-of-function mutation can be associated with a developmental defect.

scholarly journals A39 NOVEL GAIN OF FUNCTION NON-RECEPTOR TYROSINE KINASE MUTATIONS ARE LINKED TO THE PATHOGENESIS OF VEOIBD

2020 ◽  
Vol 3 (Supplement_1) ◽  
pp. 46-48
Author(s):  
M Mehta ◽  
L Wang ◽  
C Guo ◽  
N Warner ◽  
Q Li ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Western Blot ◽  
Receptor Tyrosine Kinase ◽  
Blot Analysis ◽  
Western Blot Analysis ◽  
Intestinal Inflammation ◽  
De Novo ◽  
Single Gene ◽  
Gain Of Function

Abstract Background Very early-onset inflammatory bowel disease (VEOIBD) is an emerging global disease, that results in inflammation of the digestive tract. Severe forms of VEOIBD can be caused by mutations in a single gene (monogenic variants) and, can result in death. A candidate gene which codes for a non-receptor tyrosine kinase (nRTK) has recently been implicated as a monogenic cause of IBD (unpublished). Whole exome sequencing was performed in two unrelated children who presented with symptoms of IBD identifying two distinct de novo gain of function mutations (S550Y and P342T). Both mutations are located in the highly conserved region of the nRTK, and were predicted to have similar downstream effects. Furthermore, four other patients with a variety of adult-onset immune disorders have recently been identified with rare variants in the same gene (M450I, R42P, A353T, V433M, S550F) but, their potential gain of function status remains to be determined. Studies show that this nRTK is an essential mediator in inflammation. It is expressed in both intestinal epithelial and immune cells however, its role in infantile IBD is unclear. This protein is first activated by phosphorylation and is linked to activating downstream transcription factors such as ERK and JNK. All these target proteins play a meaningful role in intestinal inflammation in patients with IBD. Aims Since we identified P342T and S550Y to be gain of function, we wanted to determine if the new variants exhibit a similar downstream impact on target protein expression levels when compared with S550Y and P342T. We also wanted to identify if all variants can be rescued with a known nRTK inhibitor. It is hypothesized that the new variants are gain of function and that all variants can be rescued with the inhibitor. Methods Using western blot analysis, the activation of ERK, JNK and nRTK was compared between wildtype (WT) and mutants. This in vitro method helped identify the degree of activation. For the second part of the study, HEK293T cells were treated with inhibitor to test for a rescue of phenotypes via western blot analysis. Results Results show an increased activation of nRTK, ERK and JNK in all variants with S550Y and S550F having the highest activation. Furthermore, pharmacological inhibition using small molecular kinase inhibitors resulted in decreased activation of nRTK, ERK and JNK suggesting a rescue of phenotypes. Conclusions Characterizing the downstream functional impact of these nRTK variants is an important first step to determine if gain of function nRTK mutations drive IBD. With a rising prevalence of IBD worldwide, these findings may lead to the development of pharmacological nRTK inhibitors as a novel personalized therapeutic approach for these patients and possibly for the broader IBD population. Funding Agencies CIHR

The receptor tyrosine kinase HIR-1 coordinates HIF-independent responses to hypoxia and extracellular matrix injury

2018 ◽  
Vol 11 (550) ◽  
pp. eaat0138
Author(s):  
Roman Vozdek ◽  
Yong Long ◽  
Dengke K. Ma
Keyword(s):  
Extracellular Matrix ◽  
Tyrosine Kinase ◽  
Receptor Tyrosine Kinase ◽  
Large Scale ◽  
Hypoxia Inducible Factor ◽  
Metabolic Adaptation ◽  
Loss Of Function ◽  
Ecm Remodeling ◽  
C Elegans ◽  
Heme Peroxidases

Inadequate tissue oxygen, or hypoxia, is a central concept in the pathophysiology of ischemic disorders and cancer. Hypoxia promotes extracellular matrix (ECM) remodeling, cellular metabolic adaptation, and cancer cell metastasis. To discover new pathways through which cells respond to hypoxia, we performed a large-scale forward genetic screen inCaenorhabditis elegansand identified a previously uncharacterized receptor tyrosine kinase named HIR-1. Loss of function inhir-1phenocopied the impaired ECM integrity associated with hypoxia or deficiency in the oxygen-dependent dual oxidase, heme peroxidases, or cuticular collagens involved in ECM homeostasis. Genetic suppressor screens identified NHR-49 and MDT-15 as transcriptional regulators downstream of HIR-1. Furthermore,hir-1mutants showed defects in adapting to and recovering from prolonged severe hypoxia. We propose thatC. elegansHIR-1 coordinates hypoxia-inducible factor–independent responses to hypoxia and hypoxia-associated ECM remodeling through mechanisms that are likely conserved in other organisms.

scholarly journals Amalgam regulates the receptor tyrosine kinase pathway through Sprouty in glial cell development in the Drosophila larval brain

2020 ◽  
Vol 133 (19) ◽  
pp. jcs250837
Author(s):  
Majd M. Ariss ◽  
Alexander R. Terry ◽  
Abul B. M. M. K. Islam ◽  
Nissim Hay ◽  
Maxim V. Frolov
Keyword(s):  
Cell Proliferation ◽  
Tyrosine Kinase ◽  
Glial Cell ◽  
Receptor Tyrosine Kinase ◽  
Cell Development ◽  
Negative Regulator ◽  
Larval Brain ◽  
Adhesion Protein ◽  
Type Composition ◽  
Signaling Activation

ABSTRACTThe receptor tyrosine kinase (RTK) pathway plays an essential role in development and disease by controlling cell proliferation and differentiation. Here, we profile the Drosophila larval brain by single-cell RNA-sequencing and identify Amalgam (Ama), which encodes a cell adhesion protein of the immunoglobulin IgLON family, as regulating the RTK pathway activity during glial cell development. Depletion of Ama reduces cell proliferation, affects glial cell type composition and disrupts the blood–brain barrier (BBB), which leads to hemocyte infiltration and neuronal death. We show that Ama depletion lowers RTK activity by upregulating Sprouty (Sty), a negative regulator of the RTK pathway. Knockdown of Ama blocks oncogenic RTK signaling activation in the Drosophila glioma model and halts malignant transformation. Finally, knockdown of a human ortholog of Ama, LSAMP, results in upregulation of SPROUTY2 in glioblastoma cell lines, suggesting that the relationship between Ama and Sty is conserved.

scholarly journals A Novel Activating Mutation in the RET Tyrosine Kinase Domain Mediates Neoplastic Transformation

2006 ◽  
Vol 20 (7) ◽  
pp. 1633-1643 ◽  
Author(s):  
Aaron Cranston ◽  
Cristiana Carniti ◽  
Sam Martin ◽  
Piera Mondellini ◽  
Yvette Hooks ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Cell Line ◽  
Glial Cell ◽  
Neurotrophic Factor ◽  
Functional Characterization ◽  
Kinase Domain ◽  
Tyrosine Kinase Domain ◽  
Exogenous Substrate

Abstract We report the finding of a novel missense mutation at codon 833 in the tyrosine kinase of the RET proto-oncogene in a patient with a carcinoma of the thyroid. In vitro experiments demonstrate that the R833C mutation induces transformed foci only when present in the long 3′ splice isoform and, in keeping with a model in which the receptor has to dimerize to be completely activated, glial cell line-derived neurotrophic factor stimulation leads the RETR833C receptor to a higher level of activation. Tyrosine kinase assays show that the RETR833C long isoform has weak intrinsic kinase activity and phosphorylation of an exogenous substrate is not elevated even in the presence of glial cell line-derived neurotrophic factor. Furthermore, the R833C mutation is capable of sustaining the transformed phenotype in vivo but does not confer upon the transformed cells the ability to degrade the basement membrane in a manner analogous to metastasis. Our functional characterization of the R833C substitution suggests that, like the V804M and S891A mutations, this tyrosine kinase mutation confers a weak activating potential upon RET. This is the first report demonstrating that the introduction of an intracellular cysteine can activate RET. However, this does not occur via dimerization in a manner analogous to the extracellular cysteine mutants.

Expression of the Axl Receptor Tyrosine Kinase in Human Thyroid Carcinoma

Thyroid ◽  
1999 ◽  
Vol 9 (6) ◽  
pp. 563-567 ◽  
Author(s):  
TETSUYA ITO ◽  
MASAHIRO ITO ◽  
SHINJI NAITO ◽  
AKIRA OHTSURU ◽  
YUJI NAGAYAMA ◽  
...  
Keyword(s):  
Thyroid Carcinoma ◽  
Tyrosine Kinase ◽  
Receptor Tyrosine Kinase ◽  
Human Thyroid ◽  
Axl Receptor Tyrosine Kinase
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