Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.10.1 (ERK)
 95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Growth factors of the glial cell line-derived neurotrophic factor (GDNF) family control the differentiation of neuronal cells of the central and peripheral nervous systems. Intracellular signalling of these growth factors is, at least in part, mediated by activation of the RET receptor tyrosine kinase. Here, we demonstrate that GDNF triggering inhibits the proliferation of the embryonal carcinoma cell line NT2/D1. This anti-proliferative effect is accompanied by down-regulation of the SSEA-3 antigen, a marker typical of undifferentiated NT2/D1 cells. We show that these effects are mediated by activation of RET signalling. The block of RET by a kinase-deficient dominant negative mutant impairs GDNF-dependent growth inhibition, whereas the adoptive expression of a constitutively active RET, the RET-MEN2A oncogene, promotes effects similar to those exerted by GDNF. We show that RET signalling increases the expression of the cyclin-dependent kinase inhibitor p27(kip1) in NT2/D1 cells. Both DNA synthesis inhibition and SSEA-3 down-regulation are prevented if p27(kip1) expression is blocked by an antisense construct, which demonstrates that RET-triggered effects are mediated by p27(kip1).
 ...
PMID:Glial cell line-derived neurotrophic factor induces proliferative inhibition of NT2/D1 cells through RET-mediated up-regulation of the cyclin-dependent kinase inhibitor p27(kip1). 1189 5

An oncogenic mutant of c-RET as a receptor-type tyrosine kinase, termed RET-MEN2A, displays both cell-transforming activity in vivo and strong catalytic activity in vitro. In this study, we compared the activities of mutant RET-MEN2A with substitutions of each of nine tyrosines for phenylalanine (Y1062F, Y1015F, Y981F, Y952F, Y928F, Y905F, Y900F, Y864F, and Y826F), which had been transfected into NIH 3T3 cells. In RET-MEN2A with the Y905F mutation, the cell-transforming activity was drastically reduced with a great reduction in the in vitro catalytic activity. Unexpectedly, we found that in vitro kinase activity was severely impaired in RET-MEN2A with Y981F, Y952F, or Y928F mutation, which displayed near-normal cell-transforming activity and only a partially impaired tyrosine phosphorylation level in vivo. Phosphoamino acid analysis actually demonstrated some increase in phosphotyrosine in the Y905F mutant but no or barely detectable increase in the Y981F, Y952F, or Y928F mutant after incubation for in vitro kinase assay. This suggested a crucial role of the Y981/Y952/Y928-linked structural integrity of the COOH end of the catalytic domain of RET in starting Y905 autophosphorylation. Interestingly, the apparent defect in intrinsic kinase activity in vitro in the Y981F, Y952F, or Y928F mutant, but not the reduction in activity in the Y905F mutant, could be partially repaired or restored by c-Src or, more extensively, by v-Src, which promoted Y905 phosphorylation in trans. A complex was shown to be formed between v-Src and RET-MEN2A through association of both with a cholesterol-rich membrane microdomain known as "a raft," possibly for efficient contact of submembranous domains of Src and RET to promote phosphorylation of Y905 of the latter. Finally, endogenous c-Src was shown to promote Y905 phosphorylation of the Y981F mutant in vivo. These results reveal a novel Src kinase-mediated repair mechanism of otherwise function-impaired mutant RET kinases.
 ...
PMID:Repair by Src kinase of function-impaired RET with multiple endocrine neoplasia type 2A mutation with substitutions of tyrosines in the COOH-terminal kinase domain for phenylalanine. 1195 5

Multiple endocrine neoplasia type 2A (MEN 2A) is associated with specific germline missense mutations in the RET proto-oncogene. This locus encodes a receptor tyrosine kinase whose activation requires the formation of a multimeric receptor complex including GDNF as a ligand and GFR alpha 1 as a coreceptor. In order to explore the role of RET, GFR alpha 1 and GDNF genes in the variation of phenotypes observed in MEN2A families, we analysed germline mutations of these genes in 4 unrelated Spanish MEN2A families (23 cases studied). We found 2 novel variants corresponding to a single change in position + 47 (intron 12) of RET and position +22 (intron 7) of GFR alpha 1. Furthermore, we observed strong co-segregation between 2 polymorphisms of RET [G691S (exon 11) and S904S (TCC-TCG, exon 15) (100%, Fisher's exact test, p< 0.001)]. More interestingly, we found that these polymorphisms occurred at a significantly high frequency in patients with age at onset < 20 years old (Kruskal-Wallis's and Fisher's exact test, p = 0.007). These findings suggest that the G691S and S904S variants of RET may somehow play a role on the age of onset of MEN 2A.
 ...
PMID:Genetic analysis of RET, GFR alpha 1 and GDNF genes in Spanish families with multiple endocrine neoplasia type 2A. 1197 48

The RET proto-oncogene encodes a receptor tyrosine kinase required for development of the kidney and neural crest-derived cell types. Alternative splicing of the 3' exons of human RET results in three protein isoforms with distinct C-termini: RET9, RET51, and RET43. These RET isoforms show differential binding to downstream adapter molecules, suggesting they may have distinct signaling functions. We have characterized Ret 3' sequences in mouse and investigated alternative splicing of this region. We found that the organization of Ret 3' sequences is very similar to human RET. The mouse locus also has alternatively spliced C-terminal coding regions, and the sequences corresponding to RET9 and RET51 are highly conserved in both position and sequence with the human locus. Further, we compared the predicted C-terminal amino acids of RET9 and RET51 in seven vertebrate species, and found that they are well conserved. We have identified sequence encoding a putative ret43 isoform in mouse, however the predicted amino acid sequence showed low homology to human RET43. Our data suggest that RET isoforms are evolutionarily highly conserved over a broad range of species, which may indicate that each isoform has a distinct role in normal RET function.
 ...
PMID:Conservation of RET proto-oncogene splicing variants and implications for RET isoform function. 1206 95

Using a yeast two-hybrid screen, we identified Dok1 as a docking protein for RET tyrosine kinase. Dok1 bound more strongly to RET with a multiple endocrine neoplasia (MEN) 2B mutation than RET with a MEN2A mutation and was highly phosphorylated in the cells expressing the former mutant protein. Analysis by site-directed mutagenesis revealed that tyrosine 361 in mouse Dok1 represents a binding site for the Nck adaptor protein and tyrosines 295, 314, 361, 376, 397, and 408 for the Ras-GTPase-activating protein. We replaced tyrosine 361 or these six tyrosines with phenylalanine (designated Y361F or 6F) in Dok1 and introduced the mutant Dok1 genes into the cells expressing the wild-type RET or RET-MEN2B protein. Overexpression of Dok1 or Dok1-Y361F, but not Dok1-6F, suppressed the Ras/Erk activation induced by glial cell line-derived neurotrophic factor or RET-MEN2B, implying that this inhibitory effect requires the Ras-GTPase-activating protein binding to Dok1. In contrast, overexpression of Dok1, but not Dok1-Y361F or Dok1-6F, enhanced the c-Jun amino-terminal kinase (JNK) and c-Jun activation. This suggested that the association of Nck to tyrosine 361 in Dok1 is necessary for the JNK and c-Jun activation by glial cell line-derived neurotrophic factor or RET-MEN2B. Because a high level of the JNK phosphorylation was observed in the cells expressing RET-MEN2B, its strong activation via Nck binding to Dok1 may be responsible for aggressive properties of medullary thyroid carcinoma developed in MEN 2B.
 ...
PMID:Role of Dok1 in cell signaling mediated by RET tyrosine kinase. 1208 92

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.
 ...
PMID:Molecular mechanisms of RET activation in human cancer. 1209 36

Germ-line point mutations of the RET gene are responsible for multiple endocrine neoplasia (MEN) type 2A and 2B that develop medullary thyroid carcinoma and pheochromocytoma. We performed a differential display analysis of gene expression using NIH 3T3 cells expressing the RET-MEN2A or RET-MEN2B mutant proteins. As a consequence, we identified 10 genes induced by both mutant proteins and eight genes repressed by them. The inducible genes include cyclin D1, cathepsins B and L, and cofilin genes that are known to be involved in cell growth, tumor progression, and invasion. In contrast, the repressed genes include type I collagen, lysyl oxidase, annexin I, and tissue inhibitor of matrix metalloproteinase 3 (TIMP3) genes that have been implicated in tumor suppression. In addition, six RET-MEN2A- and five RET-MEN2B-inducible genes were identified. Among 21 genes induced by RET-MEN2A and/or RET-MEN2B, six genes including cyclin D1, cathepsin B, cofilin, ring finger protein 11 (RNF11), integrin-alpha6, and stanniocalcin 1 (STC1) genes were also induced in TGW human neuroblastoma cells in response to glial cell line-derived neurotrophic factor stimulation. Because the STC1 gene was found to be highly induced by both RET-MEN2B and glial cell line-derived neurotrophic factor stimulation, and the expression of its product was detected in medullary thyroid carcinoma with the MEN2B mutation by immunohistochemistry, this may suggest a possible role for STC1 in the development of MEN 2B phenotype.
 ...
PMID:Characterization of gene expression induced by RET with MEN2A or MEN2B mutation. 1210 9

The RET proto-oncogene encodes two major isoforms, RET9 and RET51, which differ at the carboxyl-terminal. Loss-of-function mutations in RET result in gut aganglionosis while gain of function mutations result in cancer syndromes. From studies on transgenic mice, RET9 is important for early development of the kidney and the enteric nervous system. Little is known about the function of RET isoforms in later life. Here we report the expression of RET isoforms and its signalling complex, GDNF and GFRalpha1, in foetal and adult human kidneys. We found their expression in both the developing and the adult renal collecting system. We further show that only RET51 but not RET9 could promote the survival and tubulogenesis of mIMCD3 (mouse inner medullary collecting duct) cells in collagen gel. Our results agree with the hypothesis that RET51 signalling is related to differentiation events in later kidney organogenesis. In addition, it may also have a function in the adult kidney. We further extend our study by showing increased RET and GDNF expression in collecting duct cysts of polycystic kidney patients. This suggests that GDNF/RET signalling may contribute to proliferation of the collecting duct epithelium in an autocrine/paracrine manner.
 ...
PMID:RET receptor tyrosine kinase isoforms in kidney function and disease. 1216 57

The Ret tyrosine kinase is implicated in neuronal cell survival, kidney development and tumorigenesis. Several 3' and 5' transcript variants have been described resulting from alternative splicing of the RET pre-mRNA. The 3' variants code for three C-terminal isoforms, RET51, RET9 and RET43. The 5' variants RET2/4, RET2/5 and RET2/6 result from skipping exons 3, 3-4 and 3-5, respectively. These variants code for putative Ret proteins differing in their extracellular ligand-binding domains, and their expression is strongly regulated during kidney development. Here we analyzed the presence of these RET 5' variants in normal tissues and in MEN2 and sporadic pheochromocytomas. In all tissues examined, the abundance of these transcripts remained extremely low (less than 1% of all RET transcripts) thus indicating these species as rare variants with little biological meaning. On the other hand, in tumors, the 5' RET splicing pattern differed from that of normal tissues. Indeed, we identified a RET-derived transcript that results from the aberrant retention of intron 2. This transcript is enriched in tumor samples of both familial and sporadic origin, and indicates RET as a target for RNA splicing deregulation in tumor cells.
 ...
PMID:5'-End RET splicing: absence of variants in normal tissues and intron retention in pheochromocytomas. 1218 76

Activation of tyrosine kinase receptors is associated with human tumors. Tumorigenic versions of several RTKs, such as Ret, Kit and Met carry activating mutations at highly conserved residues of the tyrosine kinase domain. We have investigated the effect of some of these mutations on the NTRK1/NGF receptor, for which no naturally occurring activating point mutations have been so far detected. We introduced the following mutations in NTRK1 tyrosine kinase domain: (i) D668N equivalent to Met D1246N associated to HPRC; (ii) D668V modelled on Kit D816V found in mastocytosis; (iii) M688T corresponding to Ret M918T associated to the cancer syndrome MEN2B. The Met-like mutation rendered the NTRK1 receptor more responsive to ligand, as observed for the corresponding mutation in Met. On the contrary the Kit-like D668V resulted as neutral mutation. Surprisingly, the MEN2B-like M688T completely abrogated NTRK1 receptor activity, resulting as a loss of function mutation. Our results show that the mutations tested, although involving conserved amino acids in highly homologous regions, exert distinct effects in different receptors, and suggest a very peculiar auto-inhibitory mechanism for NTRK1.
 ...
PMID:Gain of function mutations of RTK conserved residues display differential effects on NTRK1 kinase activity. 1244 96


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>