Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Control of cell growth and differentiation occurs via extracellular signals known as growth factors. Growth factors are high affinity ligands for transmembrane receptors belonging to the family of receptor tyrosine kinases (RTKs). A number of genetic evidences have implicated RTKs in human diseases including developmental disorders and cancer. For instance, germline missense mutations involving the Ret receptor are found in patients affected by multiple endocrine neoplasia types 2A and 2B (MEN2A and MEN2B) or familial medullary thyroid carcinomas. Somatic mutations in the Kit receptor are found in mastocytomas and in gastrointestinal tumors. Germline and sporadic mutations of the Met receptor have been described in kidney and hepatocellular carcinomas. Overexpression of the HER-2/neu receptor in breast cancer has been associated with tumor progression. The enzymatic activity of RTKs is strictly regulated and is usually inhibited under basal conditions. Receptor activation triggers a biochemical signalling cascade inside the cytoplasm, named signal transduction, which is subverted during the malignant transformation of cells. Signal transduction by RTKs is a multistep process which includes: (i) Ligand binding and receptor dimerization, (ii) receptor phosphorylation on tyrosine residues; (iii) recruitment to the receptor and activation of cytoplasmic signaling molecules that transmit signals to the nucleus. Each of the steps involved in this process can potentially be targeted to block the aberrant properties of tyrosine kinase receptors. By using the MET oncogene as a model this review focuses on the strategies that can be applied to therapeutically target RTKs.
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PMID:Receptor tyrosine kinases as therapeutic targets: the model of the MET oncogene. 1146 38

We showed that osmotic stress induces activation of c-RET and second-set activation of constitutively activated RET-MEN2B. A few percentage of RET proteins normally formed disulfide-bonded dimers in the cell, and osmotic stress promoted formation of these dimers. The disulfide-bonded dimers displayed higher levels of autophosphorylation and catalytic activity per molecule than did monomers. Osmotic stress also promoted activation and disulfide-bonded dimerization of the extracellular domain-depleted mutant RET (RET-PTC-1), suggesting that the target amino acid(s) for dimerization is located intracellularly rather than in the cysteine-rich region of the extracellular domain. In the mutant c-RET and RET-PTC-1 in which Cys987 of c-RET or Cys376 of RET-PTC-1 was replaced with Ala, the levels of intrinsic kinase activity were greatly reduced and barely increased in response to osmotic stress. Correspondingly, the Cys376-defective RET-PTC-1 did not form any demonstrable levels of dimers even after exposure to osmotic stress. In contrast, another RET-PTC-1 mutant that had a replacement of Cys365 with Ala mostly behaved like parental RET-PTC-1. These results suggest that Cys987 of c-RET or Cys376 of RET-PTC-1 plays a crucial role in maintenance and promotion of dimerization and activation of the RET kinases.
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PMID:Osmotic stress-mediated activation of RET kinases involves intracellular disulfide-bonded dimer formation. 1149 58

Gain-of-function mutations in the gene encoding the receptor tyrosine kinase RET have been identified as the aetiological factor for multiple endocrine neoplasia type 2A (MEN2A). MEN2A is a dominantly-inherited cancer predisposition syndrome characterized by medullary thyroid carcinoma, a tumour of the calcitonin-producing thyroid C-cells. There are three isoforms of RET: RET9, RET43 and RET51, and although in vitro evidence suggests they vary in cellular transformation activities, little is known about their function in tumorigenesis in vivo. To address this, we used RET51 cDNA to construct mice in which the most frequent MEN2A mutation, Cys-634-Arg, was expressed under the control of the human calcitonin promoter (CT-2A mice). These mice developed C-cell tumours resembling human MTC and follicular tumours resembling human papillary thyroid carcinoma (PTC) depending on the founder line examined. One founder line developed compound MTC/PTC at low frequency (8%) and pancreatic cystadenocarcinoma. CT-2A mice also displayed a developmental defect in thyroid follicular structure, in which much of the thyroid was occupied by large irregular cystic follicles thought to be derived from the ultimobranchial body, a developmental precursor of the thyroid gland. The CT-2A mice will provide a suitable model to further study the effects of the MEN 2A RET mutation in vivo.
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PMID:C-cell and thyroid epithelial tumours and altered follicular development in transgenic mice expressing the long isoform of MEN 2A RET. 1149 27

Medullary thyroid carcinoma (MTC) occurs usually in sporadic form, but about a quarter of the cases are hereditary and appear as part of one of the multiple endocrine neoplasia type 2 (MEN2) syndromes. Mutations in the RET protooncogene are known to be the cause of the MEN2A and familial medullary thyroid carcinoma (FMTC) syndromes in the majority of the families. Direct DNA testing allows prophylactic thyroidectomy to be offered to individuals carrying a mutation in the above codons, and in mutation-negative cases it reduces the yearly screening-related burden on family members at risk of the disease. By DNA sequencing and PCR-restriction fragment length polymorphisms, 65 MTC probands were examined for mutations in residues 609, 611, 618, 620 of exon 10, and in residues 634, 768, 804 of exons 11, 13, and 14 respectively of the RET protooncogene. In our study, mutations in the above codons were detected in all of the 14 clinically MEN2A and FMTC families. One of these mutations, TGC609 TCC has not been reported previously. Of the 14 probands with the mutation, 25 relatives also had the identified mutation and 18 relatives proved to be non-carriers. Among the 51 probands with clinically sporadic MTC, none was found to carry a mutation in the above positions even if indirect signs of MTC, pheochromocytoma or hyperparathyroidism could be detected in some families. The frequency of the TGC634AGC mutation is unexpectedly high in our samples, which can probably be attributed to a founder effect. We conclude that screening for mutations in these codons is effective in families fulfilling the strict clinical criteria of MEN2A or FMTC.
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PMID:Molecular genetic diagnostic program of multiple endocrine neoplasia type 2A and familial medullary thyroid carcinoma syndromes in Hungary. 1152 47

The MEN2A oncogene encodes for a constitutive active member of the RET receptor tyrosine kinase family. Here, we report that MEN2A-RET activates Signal Transducer and Activator of Transcription 3 (STAT3) via two YxxV/Q STAT3 docking sites, Tyr752 and Tyr928. MEN2A-RET induces both Tyr705 and Ser727 phosphorylation of STAT3, and STAT3 serine phosphorylation is required for its maximal transcriptional activity. Stable NIH3T3 cell lines expressing both MEN2A-RET and STAT3alpha but not STAT3beta, are characterized by enhanced proliferation and cyclin-D1 promoter activity, and enhanced growth in soft agar. These data indicate that malignant cell growth induced by MEN2A-RET involves its activation of STAT3.
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PMID:MEN2A-RET-induced cellular transformation by activation of STAT3. 1153 47

The RET receptor tyrosine kinase has a critical role in kidney organogenesis and the development of the enteric nervous system. Two major isoforms, RET9 and RET51, differ in the amino acid sequence of the C-terminal tail as a result of alternative splicing. To determine the roles of these isoforms in vivo, we used targeted mutagenesis to generate mice that express either RET9 or RET51. Monoisoformic RET9 mice, which lack RET51, are viable and appear normal. In contrast, monoisoformic RET51 animals, which lack RET9, have kidney hypodysplasia and lack enteric ganglia from the colon. To study the differential activities of the two RET isoforms further, we generated transgenic mice expressing ligand-dependent and constitutively active forms of RET9 or RET51 under the control of the Hoxb7 regulatory sequences. Such RET9 transgenes are capable of rescuing the kidney agenesis in RET-deficient mice or causing kidney hypodysplasia in wild-type animals. In contrast, similar RET51 transgenes fail to rescue the kidney agenesis or cause hypodysplasia. Our findings show that RET9 and RET51 have different signaling properties in vivo and define specific temporal and spatial requirements of c-Ret function during renal development and histogenesis of the enteric nervous system.
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PMID:Differential activities of the RET tyrosine kinase receptor isoforms during mammalian embryogenesis. 1156 52

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., Cys(609), Cys(620), and Cys(634)) 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 Cys(609)- or Cys(620)-activating mutations with HSCR is still an unresolved paradox. To address this issue, we have compared these two mutants with the Cys(634) 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 Cys(634) Ret variant can trigger antiapoptotic pathways only in response to GDNF. In contrast, Cys(609) or Cys(620) 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.
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PMID:The sensitivity of activated Cys Ret mutants to glial cell line-derived neurotrophic factor is mandatory to rescue neuroectodermic cells from apoptosis. 1156 57

This is a consensus statement from an international group, mostly of clinical endocrinologists. MEN1 and MEN2 are hereditary cancer syndromes. The commonest tumors secrete PTH or gastrin in MEN1, and calcitonin or catecholamines in MEN2. Management strategies improved after the discoveries of their genes. MEN1 has no clear syndromic variants. Tumor monitoring in MEN1 carriers includes biochemical tests yearly and imaging tests less often. Neck surgery includes subtotal or total parathyroidectomy, parathyroid cryopreservation, and thymectomy. Proton pump inhibitors or somatostatin analogs are the main management for oversecretion of entero-pancreatic hormones, except insulin. The roles for surgery of most entero-pancreatic tumors present several controversies: exclusion of most operations on gastrinomas and indications for surgery on other tumors. Each MEN1 family probably has an inactivating MEN1 germline mutation. Testing for a germline MEN1 mutation gives useful information, but rarely mandates an intervention. The most distinctive MEN2 variants are MEN2A, MEN2B, and familial medullary thyroid cancer (MTC). They vary in aggressiveness of MTC and spectrum of disturbed organs. Mortality in MEN2 is greater from MTC than from pheochromocytoma. Thyroidectomy, during childhood if possible, is the goal in all MEN2 carriers to prevent or cure MTC. Each MEN2 index case probably has an activating germline RET mutation. RET testing has replaced calcitonin testing to diagnose the MEN2 carrier state. The specific RET codon mutation correlates with the MEN2 syndromic variant, the age of onset of MTC, and the aggressiveness of MTC; consequently, that mutation should guide major management decisions, such as whether and when to perform thyroidectomy.
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PMID:Guidelines for diagnosis and therapy of MEN type 1 and type 2. 1205 Feb 90

The RET gene encodes a receptor tyrosine kinase involved in normal and neoplastic development of neural crest cell lineages. Activating RET mutations are present in patients with multiple endocrine neoplasia types 2A and 2B (MEN2A, 2B) and in familial medullary thyroid carcinoma (FMTC) patients, whereas inactivating RET mutations are found in patients with Hirschsprung (HSCR) disease. In particular for MEN2A and FMTC, the clinical management largely depends on the specific mutation found.
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PMID:[From gene to disease; from the RET gene to multiple endocrine neoplasia types 2A and 2B, sporadic and familial medullary thyroid carcinoma, Hirschsprung disease and papillary thyroid carcinoma]. 1175 48

Multiple endocrine neoplasia type 2 (MEN2) syndromes are inherited in an autosomal dominant fashion with high penetrance. There are three subtypes, namely, MEN2A (multiple endocrine neoplasia type 2A), MEN2B (multiple endocrine neoplasia type 2B), and familial medullary thyroid carcinoma. The variations in the RET gene play an important role in the MEN2 syndromes. In this work, we have developed a RET oligonucleotide microarray of 67 oligonucleotides to quickly detect RET mutations in MEN2 syndromes. The predominant RET mutations are missense mutations and are restricted to nine codons (codons 609, 611, 618, 620, 630, 634, 768, 804, and 918) in MEN2 syndromes. Missense mutations at codons 609, 611, 618, 620, and 634 have been identified in 98% of MEN2A families and in 85% of familial medullary thyroid carcinoma families. More than 95% of MEN2B patients also had a predominant mutation type at codon 918 (Met-->Thr). RET oligonucleotide microarray can detect RET missense mutations at these nine codons. Theoretically, a total of 55 missense mutation types can occur at eight codons (codons 609, 611, 618, 620, 630, 634, 768, and 804). RET oligonucleotide microarray is designed to detect all of these 55 missense mutation types at these eight codons and one predominant type at codon 918. Fifty-six oligonucleotides were designed for the 56 mutation types at nine codons, and 11 oligonucleotides were designed for the wild types and positive controls. We found RET mutations in all eight of the Korean MEN2A families (a total of 75 members; 27 affected members, 19 gene carriers, and 29 unaffected members) using the developed RET oligonucleotide microarray and an automatic sequencing. Because we found only five mutation types from eight MEN2A families, the international collaborations are required to see whether the RET oligonucleotide microarray may be used as a genetic diagnostic tool. Taken together, the RET oligonucleotide microarray can function as a fast and reliable genetic diagnostic device, which simplifies the process of detecting RET mutations.
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PMID:RET oligonucleotide microarray for the detection of RET mutations in multiple endocrine neoplasia type 2 syndromes. 1183 64


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