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)

Multiple endocrine neoplasia type 2A (MEN 2A) is a dominantly inherited cancer syndrome, which involves the triad of MTC, pheochromocytoma, and hyperparathyroidism. Missense mutations in one of six cysteine codons in the extracellular cysteine-rich domain of the RET proto-oncogene predispose to this disease. These mutations cause ligand-independent constitutive activation of the tyrosine kinase receptor by the formation of disulfide-bonded homodimers. We examined a different type of mutation, which results in an additional cysteine in the cysteine rich domain. A duplication of 9 bp in the first case resulted in an insertion of three amino acids between codon 633 and 634. In the second case a 12 bp duplication in exon 11 results in four additional amino acids between codon 634 and 635. Here we demonstrate that an additional cysteine causes a ligand independent dimerization of the RET receptor in transfected NIH3T3 cells, which results in an activation of the intracellular tyrosine kinase.
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PMID:A novel type of mutation in the cysteine rich domain of the RET receptor causes ligand independent activation. 1091 2

Hirschsprung disease (HSCR; McKusick 142623) or aganglionic megacolon is a frequent (1 in 5,000 live births) heritable disorder of the enteric nervous system. By haplotyping with a variety of microsatellite markers, by amplifying all 20 exons of the RET proto-oncogene and by applying a direct DNA sequencing protocol, we have analyzed the DNA from HSCR patients in 6 different families. In one family with a joint occurrence of HSCR and FMTC (follicular medullary thyroid carcinoma), we have identified a mutation in codon 609 in one out of 6 cysteine residues encoded in exon 10 of the RET gene. This C609R point mutation has not previously been reported to cause HSCR. In 2 of the HSCR patients described here from different families, we have found a mutation in exon 2 (R77C) and a silent mutation in exon 3 (Y204Y), respectively, in the extracellular part of the RET proto-oncogene. In introns 2 and 17 of the RET proto-oncogene in 2 families, we have detected single nucleotide exchanges that are probably polymorphisms with unknown, if any, relations to HSCR. The DNA sequences of 5 further genes (GDNF, GDNFRalpha, EDN3, EDNRB, and NTN), that may contribute to the development of HSCR, have not shown mutations in the patients analyzed so far. In 2 of the reported families with several affected children and one grandchild, sequence analyses revealed no mutations in the coding regions of any of the candidate genes analyzed.
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PMID:Familial form of hirschsprung disease: nucleotide sequence studies reveal point mutations in the RET proto-oncogene in two of six families but not in other candidate genes. 1098 77

Much is yet to be learned about cancer and its genetic basis. The discovery of the RET proto-oncogene and its role in tumorigenesis have improved our understanding of thyroid cancer. It is clear that RET is responsible for MEN 2A, MEN 2B, FMTC, and PTC. Although the physical and genetic map of the RET proto-oncogene has been elucidated, the precise mechanism of neoplastic transformation and how it affects phenotypic variability is not completely understood. From the precise mapping of RET arose a highly reliable method of DNA analysis for presymptomatic detection of disease allele carriers. The understanding of the role of the RET proto-oncogene in MEN syndromes has led to a new paradigm in surgical practice: the recommendation for surgery based solely on genetic testing.
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PMID:Perspective on RET proto-oncogene and thyroid cancer. 1106 17

Germline mutations of the RET proto-oncogene cause three different cancer syndromes: multiple endocrine neoplasia type 2A (MEN 2A), multiple endocrine neoplasia type 2B (MEN 2B) and familial medullary thyroid carcinoma (FMTC). In the absence of biochemical and/or clinical evidence of pheochromocytoma and hyperparathyroidism, patients with MEN 2A disease display the same phenotype of FMTC disease, although prognosis and clinical management in both affected and unaffected familial members are quite different. We studied a family with hereditary MTC, whose proband was referred to us because of enlarged cervical nodes and increased calcitonin serum levels 28 years after the total thyroidectomy for MTC. Cervical node dissection was carried out and subsequently the presence of MTC metastasis was histologically confirmed. A RET genomic mutation at codon 634 (TGC-->TTC) was identified in the proband and in seven out of 19 familial members studied. Accordingly, a hereditary disease was suggested. However, the strong association of RET mutation at codon 634 with the presence of pheochromocytoma in MEN 2 disease suggested a more rigorous management in all gene carriers. Indeed, during the follow-up pheochromocytoma was subsequently identified in the proband. This finding suggests that all families with a pedigree suggestive of FMTC should be regarded at risk from MEN 2A disease, at least when a critical mutation in the RET cysteine domain is detected.
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PMID:A large family with hereditary MTC: role of RET genetic analysis in differential diagnosis between MEN 2A and FMTC. 1128 Jul 16

All patients with a thyroid nodule should have their plasma CT measured. Stimulated CT is generally better than basal, but in the lower ranges false negatives and false positives still occur. In families with hereditary MTC, RET gene mutation analysis has superseded measurement of plasma CT in the detection of asymptomatic disease gene carriers. All individuals with apparently sporadic MTC, but in whom there is some suspicion of familial disease, should also have RET genetic analysis. A negative DNA result practically excludes the possibility of hereditary MTC in families where an index case has been investigated and obviates the need for further biochemical evaluation. Disease gene carriers may be divided into three distinct risk groups depending on the specific RET gene mutation in the family. The age at which presymptomatic surgery has to be performed depends on the risk group to which the patient belongs. Compared with the results of DNA analysis, the results of CT stimulation tests have become less important in the assessment of timing of surgery. During follow-up of patients who underwent surgery, measurement of plasma basal CT is still useful. The high sensitivity of measuring stimulated CT levels does not outweigh the burden of life-long periodic stimulation tests and the limited clinical consequences of slightly elevated levels. Stimulation tests are inevitable for persons at risk who prefer not to have genetic testing.
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PMID:Medullary thyroid carcinoma: role of genetic testing and calcitonin measurement. 1139 93

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

Mutations that produce oncogenes with dominant gain of function target receptor protein tyrosine kinases (PTKs) in cancer and confer uncontrolled proliferation, impaired differentiation, or unrestrained survival to the cancer cell. However, insufficient PTK signaling may be responsible for developmental diseases. Gain of function of the RET receptor PTK is associated with human cancer. At the germline level, point mutations of RET are responsible for multiple endocrine neoplasia type 2 (MEN2A, MEN2B, and FMTC). Mutations of extracellular cysteines are found in MEN2A patients, and a Met918Thr mutation is responsible for most MEN2B cases. At the somatic level, gene rearrangements juxtaposing the tyrosine kinase domain of RET to heterologous gene partners are found in papillary carcinomas of the thyroid. These rearrangements generate the chimeric RET/PTC oncogenes. Both MEN2 mutations and PTC gene rearrangements potentiate the intrinsic tyrosine kinase activity of RET and, ultimately, the RET downstream signaling events. A multidocking site of the C-tail of RET is essential for both mitogenic and survival RET signaling. Such a site is involved in the recruitment of several intracellular molecules, such as the Shc, FRS2, IRS1, Gab1/2, and Enigma. The different activating mutations not only potentiate the enzymatic activity of the RET kinase but also may alter qualitatively RET signaling properties by: (1) altering RET autophosphorylation (in the case of the MEN2B mutation), (2) modifying the subcellular distribution of the active kinase, and (3) providing the active kinase with a scaffold for novel protein-protein interactions (as in the case of RET/PTC oncoproteins). This review describes the molecular mechanisms by which the different genetic alterations cause the conversion of RET into a dominant transforming oncogene.
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PMID:Molecular mechanisms of RET activation in human cancer. 1209 36

The RET proto-oncogene has not only conclusively been identified as responsible for the three subtypes of the inherited cancer syndrome multiple endocrine neoplasia type 2 (MEN-2) but also shown to be involved in the molecular evolution of sporadic medullary and papillary thyroid carcinoma as well as Hirschsprung's disease. A variety of recent studies have elucidated the pathophysiological mechanisms leading to neoplastic disease and we now understand that dominant activating germline mutations lead to MEN-2A, MEN-2B, and familial MTC; somatic mutations to sporadic medullary thyroid carcinoma; RET rearrangements to papillary thyroid carcinoma; and inactivating alterations to Hirschsprung's disease. The clinical significance, however, of RET alterations especially in sporadic thyroid tumors is still controversial and therapeutic concepts in MEN-2 gene carriers only start to emerge. This article is a short summary of the recent findings on the structure and physiology of the RET proto-oncogene and its role in familial and sporadic thyroid cancer.
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PMID:RET Proto-Oncogene and Thyroid Cancer. 1211 28

Transcription factors play important roles in regulating cell growth and differentiation. In this study, treatment of the MTC cell line, TT, with phorbol 12-myristate 13-acetate (PMA) was shown to reduce neurite outgrowth which may be associated with de-differentiation and loss of the transformed phenotype. Northern blotting revealed that PMA transiently induced early growth response gene 1 (Egr-1) expression and decreased RET expression. Transient transfection analyses using 5'-deletion constructs of the basal RET promoter, demonstrated the requirement of a region between -70 and -33 bp for PMA-inducible expression. Gel shift and supershift studies demonstrated that PMA induced Egr-1 formed part of a complex capable of binding to the RET minimal promoter. Overexpression of Egr-1 displaced both sephacryl and phosphocellulose protein 1 (Sp1) and Sp3 from a GC-box element previously found to be important for RET basal expression. Furthermore, use of a raf-1 inducible TT cell line, that has been previously shown to downregulate RET expression, revealed that this downregulation may be linked to the induction of Egr-1. Our data suggest that regulation of RET expression during development and in medullary thyroid carcinoma may be determined, at least in part, by this complex of Sp and Egr-1 proteins.
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PMID:Transcriptional repression of the RET proto-oncogene by a mitogen activated protein kinase-dependent signalling pathway. 1240 71

The etiology of sporadic medullary thyroid carcinoma (sMTC) remains elusive. While germline gain-of-function mutations in the RET proto-oncogene cause hereditary MTC, somatic RET mutations have been described in a variable number of sMTC. So far, S836S of RET, is the only variant whose association with sMTC has been found in several European cohorts. Because RET variants seem to be associated with MTC, it is plausible that variants in genes encoding for RET coreceptors may play a role in the pathogenesis of sMTC. Recently, we described two possible low penetrance susceptibility alleles in the gene encoding RET coreceptor GFRalpha1, -193C > G and 537T > C, in a German series of sMTC. In this study, we have genotyped nine polymorphisms within GFRA1-3 genes for 51 Spanish sMTC, and 100 normal controls. Our results show that no statistical signification was found when Spanish sMTC patients were compared to controls. Taken together with the observations in the German sMTC series, the present findings suggest that GFRA1-193C > G and 537T > C could be in linkage disequilibrium with other loci responsible for the disease with a founder effect in Germany. Alternatively, the combined observations might also suggest that, if indeed the polymorphisms are functional, the effect is small.
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PMID:Evaluation of germline sequence variants of GFRA1, GFRA2, and GFRA3 genes in a cohort of Spanish patients with sporadic medullary thyroid cancer. 1249 80


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