RESUMO
Rhophilin 2 is a Rho GTPase binding protein initially isolated by differential screening of a chronically thyrotropin (TSH)-stimulated dog thyroid cDNA library. In thyroid cell culture, expression of rhophilin 2 mRNA and protein is enhanced following TSH stimulation of the cyclic AMP (cAMP) transduction cascade. Yeast two-hybrid screening and coimmunoprecipitation have revealed that the GTP-bound form of RhoB and components of the cytoskeleton are protein partners of rhophilin 2. These results led us to suggest that rhophilin 2 could play an important role downstream of RhoB in the control of endocytosis during the thyroid secretory process which follows stimulation of the TSH/cAMP pathway. To validate this hypothesis, we generated rhophilin 2-deficient mice and analyzed their thyroid structure and function. Mice lacking rhophilin 2 develop normally, have normal life spans, and are fertile. They have no visible goiter and no obvious clinical signs of hyper- or hypothyroidism. The morphology of thyroid cells and follicles in these mice were normal, as were the different biological tests performed to investigate thyroid function. Our results indicate that rhophilin 2 does not play an essential role in thyroid physiology.
Assuntos
Proteínas Imediatamente Precoces/deficiência , Proteínas Serina-Treonina Quinases/deficiência , Glândula Tireoide/citologia , Glândula Tireoide/fisiologia , Proteínas Adaptadoras de Transdução de Sinal , Animais , Encéfalo/citologia , Encéfalo/metabolismo , DNA Complementar/genética , Feminino , Perfilação da Expressão Gênica , Genótipo , Proteínas Imediatamente Precoces/genética , Proteínas Imediatamente Precoces/metabolismo , Rim/citologia , Rim/metabolismo , Pulmão/citologia , Pulmão/metabolismo , Masculino , Camundongos , Camundongos Knockout , Ovário/citologia , Ovário/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Testículo/citologia , Testículo/metabolismo , Glândula Tireoide/metabolismoRESUMO
Genetic susceptibility to type 2 diabetes involves many genes, most of which are still unknown. The lipid phosphatase SHIP2 is a potent negative regulator of insulin signaling and sensitivity in vivo and is thus a good candidate gene. Here we report the presence of SHIP2 gene mutations associated with type 2 diabetes in rats and humans. The R1142C mutation specifically identified in Goto-Kakizaki (GK) and spontaneously hypertensive rat strains disrupts a potential class II ligand for Src homology (SH)-3 domain and slightly impairs insulin signaling in cell culture. In humans, a deletion identified in the SHIP2 3' untranslated region (UTR) of type 2 diabetic subjects includes a motif implicated in the control of protein synthesis. In cell culture, the deletion results in reporter messenger RNA and protein overexpression. Finally, genotyping of a cohort of type 2 diabetic and control subjects showed a significant association between the deletion and type 2 diabetes. Altogether, our results show that mutations in the SHIP2 gene contribute to the genetic susceptibility to type 2 diabetes in rats and humans.
Assuntos
Mapeamento Cromossômico , Diabetes Mellitus Tipo 2/genética , Monoéster Fosfórico Hidrolases/genética , Regiões 3' não Traduzidas/genética , Animais , Sequência de Bases , Células CHO , Linhagem Celular , Estudos de Coortes , Cricetinae , Diabetes Mellitus Tipo 2/enzimologia , Amplificação de Genes , Genes Reporter , Genótipo , Humanos , Hibridização in Situ Fluorescente , Rim/embriologia , Rim/enzimologia , Luciferases/genética , Camundongos , Dados de Sequência Molecular , Fosfatidilinositol-3,4,5-Trifosfato 5-Fosfatases , Monoéster Fosfórico Hidrolases/metabolismo , Ratos , Proteínas Recombinantes/metabolismo , Valores de Referência , Deleção de Sequência , Transfecção , Domínios de Homologia de src/genéticaRESUMO
The hypothalmo-pituitary thyroid axis, among various endocrine systems, undergoes physiological alterations associated with the ageing process. Directly age-related changes have to be distinguished from indirect modifications which are caused by simultaneous thyroidal or non-thyroidal illness or other physiological or pathophysiological states whose incidence increases with age. In summary, direct changes of the hypothalmo-pituitary-thyroid axis seem to be subtle and suggestive of a decreased hypothalamic stimulation of thyroid function. In parallel, disease-specific alterations such as the development of thyroid autonomy or changes in energy intake or sleep lead to pronounced alterations of thyroid function with age which may dominate the underlying ageing of the hypothalmo-pituitary thyroid axis itself. The following article attempts to delineate some aspects of the interplay of the regulation of thyroid function and the ageing process.