| First Author | Martin NP | Year | 2014 |
| Journal | Endocrinology | Volume | 155 |
| Issue | 9 | Pages | 3713-24 |
| PubMed ID | 24932806 | Mgi Jnum | J:217014 |
| Mgi Id | MGI:5612920 | Doi | 10.1210/en.2013-2058 |
| Citation | Martin NP, et al. (2014) A rapid cytoplasmic mechanism for PI3 kinase regulation by the nuclear thyroid hormone receptor, TRbeta, and genetic evidence for its role in the maturation of mouse hippocampal synapses in vivo. Endocrinology 155(9):3713-24 |
| abstractText | Several rapid physiological effects of thyroid hormone on mammalian cells in vitro have been shown to be mediated by the phosphatidylinositol 3-kinase (PI3K), but the molecular mechanism of PI3K regulation by nuclear zinc finger receptor proteins for thyroid hormone and its relevance to brain development in vivo have not been elucidated. Here we show that, in the absence of hormone, the thyroid hormone receptor TRbeta forms a cytoplasmic complex with the p85 subunit of PI3K and the Src family tyrosine kinase, Lyn, which depends on two canonical phosphotyrosine motifs in the second zinc finger of TRbeta that are not conserved in TRalpha. When hormone is added, TRbeta dissociates and moves to the nucleus, and phosphatidylinositol (3, 4, 5)-trisphosphate production goes up rapidly. Mutating either tyrosine to a phenylalanine prevents rapid signaling through PI3K but does not prevent the hormone-dependent transcription of genes with a thyroid hormone response element. When the rapid signaling mechanism was blocked chronically throughout development in mice by a targeted point mutation in both alleles of Thrb, circulating hormone levels, TRbeta expression, and direct gene regulation by TRbeta in the pituitary and liver were all unaffected. However, the mutation significantly impaired maturation and plasticity of the Schaffer collateral synapses on CA1 pyramidal neurons in the postnatal hippocampus. Thus, phosphotyrosine-dependent association of TRbeta with PI3K provides a potential mechanism for integrating regulation of development and metabolism by thyroid hormone and receptor tyrosine kinases. |
