RESUMEN
The variety of diseases caused by mutations in RET receptor tyrosine kinase provides a classic example of phenotypic heterogeneity. Gain-of-function mutations of RET are associated with human cancer. Gene rearrangements juxtaposing the tyrosine kinase domain to heterologous gene partners have been found in sporadic papillary carcinomas of the thyroid (PTC). These rearrangements generate chimeric RET/PTC oncogenes. In the germline, point mutations of RET are responsible for multiple endocrine neoplasia type 2 (MEN 2A and 2B) and familial medullary thyroid carcinoma (FMTC). Both MEN 2 mutations and PTC gene rearrangements potentiate the intrinsic tyrosine kinase activity of RET and, ultimately, activate the RET downstream targets. Loss-of-function mutations of RET cause Hirschsprung's disease (HSCR) or colonic aganglionosis. A deeper understanding of the molecular signaling of normal versus abnormal RET activity in cancer will enable the development of potential new treatments for patients with sporadic and inherited thyroid cancer or MEN 2 syndrome. We now review the role and mechanisms of RET signaling in development and carcinogenesis.
Asunto(s)
Neoplasias/genética , Neoplasias/metabolismo , Proteínas Proto-Oncogénicas/genética , Proteínas Proto-Oncogénicas/fisiología , Proteínas Tirosina Quinasas Receptoras/genética , Proteínas Tirosina Quinasas Receptoras/fisiología , Transducción de Señal , Enfermedad de Hirschsprung/enzimología , Enfermedad de Hirschsprung/genética , Humanos , Mutación , Neoplasias/enzimología , Proteínas Proto-Oncogénicas c-ret , Transducción de Señal/fisiología , Neoplasias de la Tiroides/genética , Neoplasias de la Tiroides/metabolismoRESUMEN
The receptor tyrosine kinase RET is alternatively spliced to yield two main isoforms, RET9 and RET51, which differ in their carboxyl terminal. Activated RET induces different biological responses such as morphological transformation, neurite outgrowth, proliferation, cell migration and branching. The two isoforms have been suggested to have separate intracellular signaling pathways and different roles in mouse development. Here we show that both isoforms are able to induce cell scattering of SK-N-MC neuroepithelioma cell line and branching tubule formation in MDCK cell line. However, the Y1062F mutation, which abrogates the transforming activity of both activated RET isoforms in NIH3T3 cells, does not abolish scattering and branching morphogenesis of RET51, whereas impairs these biological effects of RET9. The GDNF-induced biological effects of RET51 are inhibited by the simultaneous abrogation of both Tyr1062 and Tyr1096 docking sites. Thus, Tyr1096 may substitute the functions of Tyr1062. GRB2 is the only known adaptor protein binding to Tyr1096. Dominant-negative GRB2 expressed in MDCK cells together with RET9 or RET51 significantly reduces branching. Therefore, GRB2 is necessary for RET-mediated branching of MDCK cells.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales , Células Epiteliales/citología , Neuronas/citología , Proteínas Oncogénicas/metabolismo , Proteínas/metabolismo , Proteínas Tirosina Quinasas Receptoras/metabolismo , Tirosina , Células 3T3 , Secuencia de Aminoácidos , Animales , Secuencia de Bases , División Celular/efectos de los fármacos , Línea Celular , Movimiento Celular/fisiología , Clonación Molecular , Cartilla de ADN , Perros , Células Epiteliales/efectos de los fármacos , Células Epiteliales/fisiología , Proteína Adaptadora GRB2 , Factor Neurotrófico Derivado de la Línea Celular Glial , Riñón , Ratones , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Factores de Crecimiento Nervioso/farmacología , Neuritas/ultraestructura , Neuronas/efectos de los fármacos , Neuronas/fisiología , Proteínas Oncogénicas/genética , Isoformas de Proteínas/metabolismo , Proteínas/genética , Proteínas Proto-Oncogénicas c-ret , Proteínas Tirosina Quinasas Receptoras/genética , Proteínas Recombinantes de Fusión/metabolismo , Proteínas Quinasas p38 Activadas por MitógenosRESUMEN
Gain-of-function mutations of ret receptor tyrosine kinase, the signaling receptor for glial cell line-derived neurotrophic factor, cause sporadic thyroid and adrenal malignancies as well as endocrine cancer syndromes, such as multiple endocrine neoplasia types 2A and 2B (MEN 2A and MEN 2B) and familial medullary thyroid carcinoma. Loss-of-function mutations of ret cause Hirschsprung's disease (HSCR) or colonic aganglionosis. In 20-30% of families with a mutation at residues 609, 611, 618, or 620 of RET, MEN 2A and familial medullary thyroid carcinoma cosegregate with HSCR. These mutations constitutively activate RET due to aberrant disulfide homodimerization and diminish the level of RET at the plasma membrane. It is not known how these mutations simultaneously lead to both gain- and loss-of-function RET-associated diseases. We provide an explanation for the dual phenotypic Janus mutation at Cys620 of RET. In Madin-Darby canine kidney (MDCK) cells, the Janus mutation impairs the glial cell line-derived neurotrophic factor-induced effects of RET on cell migration, differentiation, and survival but simultaneously promotes rapid cell proliferation.
Asunto(s)
Enfermedad de Hirschsprung/genética , Neoplasia Endocrina Múltiple Tipo 2a/genética , Neoplasia Endocrina Múltiple Tipo 2b/genética , Proteínas Oncogénicas/genética , Proteínas Tirosina Quinasas Receptoras/genética , Animales , Dimerización , Perros , Factor Neurotrófico Derivado de la Línea Celular Glial , Enfermedad de Hirschsprung/metabolismo , Neoplasia Endocrina Múltiple Tipo 2a/metabolismo , Neoplasia Endocrina Múltiple Tipo 2b/metabolismo , Factores de Crecimiento Nervioso/metabolismo , Proteínas Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-ret , Proteínas Tirosina Quinasas Receptoras/metabolismoAsunto(s)
Carcinoma Medular/genética , Mutación Puntual , Proteínas Proto-Oncogénicas/genética , Proteínas Tirosina Quinasas Receptoras/genética , Transducción de Señal , Neoplasias de la Tiroides/genética , Carcinoma Medular/patología , Humanos , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-ret , Proteínas Tirosina Quinasas Receptoras/metabolismo , Neoplasias de la Tiroides/patologíaRESUMEN
Glial cell line-derived neurotrophic factor (GDNF) and hepatocyte growth factor (HGF) are multifunctional signaling molecules in embryogenesis. HGF binds to and activates Met receptor tyrosine kinase. The signaling receptor complex for GDNF typically includes both GDNF family receptor alpha1 (GFRalpha1) and Ret receptor tyrosine kinase. GDNF can also signal independently of Ret via GFRalpha1, although the mechanism has remained unclear. We now show that GDNF partially restores ureteric branching morphogenesis in ret-deficient mice with severe renal hypodysplasia. The mechanism of Ret-independent effect of GDNF was therefore studied by the MDCK cell model. In MDCK cells expressing GFRalpha1 but no Ret, GDNF stimulates branching but not chemotactic migration, whereas both branching and chemotaxis are promoted by GDNF in the cells coexpressing Ret and GFRalpha1, mimicking HGF/Met responses in wild-type MDCK cells. Indeed, GDNF induces Met phosphorylation in several ret-deficient/GFRalpha1-positive and GFRalpha1/Ret-coexpressing cell lines. However, GDNF does not immunoprecipite Met, making a direct interaction between GDNF and Met highly improbable. Met activation is mediated by Src family kinases. The GDNF-induced branching of MDCK cells requires Src activation, whereas the HGF-induced branching does not. Our data show a mechanism for the GDNF-induced branching morphogenesis in non-Ret signaling.
Asunto(s)
Proteínas de Drosophila , Riñón/anomalías , Factores de Crecimiento Nervioso/metabolismo , Proteínas Proto-Oncogénicas c-met/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Tirosina Quinasas Receptoras/metabolismo , Uréter/anomalías , Urotelio/anomalías , Familia-src Quinasas/metabolismo , Animales , Tipificación del Cuerpo/efectos de los fármacos , Tipificación del Cuerpo/genética , Diferenciación Celular/efectos de los fármacos , Diferenciación Celular/genética , Quimiotaxis/efectos de los fármacos , Quimiotaxis/genética , Perros , Factor Neurotrófico Derivado de la Línea Celular Glial , Receptores del Factor Neurotrófico Derivado de la Línea Celular Glial , Factor de Crecimiento de Hepatocito/metabolismo , Humanos , Riñón/citología , Riñón/metabolismo , Fosforilación/efectos de los fármacos , Proteínas Proto-Oncogénicas/deficiencia , Proteínas Proto-Oncogénicas/genética , Proteínas Proto-Oncogénicas c-ret , Proteínas Tirosina Quinasas Receptoras/deficiencia , Proteínas Tirosina Quinasas Receptoras/genética , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Transfección , Células Tumorales Cultivadas , Uréter/citología , Uréter/metabolismo , Urotelio/efectos de los fármacos , Urotelio/metabolismoRESUMEN
The receptor tyrosine kinase RET, with a known role in embryonic development and in human pathologies, is alternatively spliced to yield at least two functional isoforms, which differ only in their carboxyl terminal. Enigma protein is a member of the PDZ-LIM family and is known to interact with the short isoform of RET/PTC2, a chimeric oncoprotein isolated from papillary thyroid carcinoma. Here, we show that Enigma also interacts in intact cells with the short isoform of RET-wt and of its pathologic mutants associated to MEN2 syndromes, RET-C634R and RET-M918T. In contrast, Enigma binds all the corresponding RET long isoforms very poorly and colocalizes with short but not long RET/PTC2 isoforms. The RET docking tyrosine for Enigma is the last but one before the divergence between the two isoforms and we demonstrated that short-isoform-specific amino acid residues +2 to +4 to this tyrosine are required for the interaction of RET/PTC2 with Enigma.