The action of vitamin D is mediated through binding to its nuclear receptor (VDR).
The transcriptional actions of the bioactive hormone T3 are mediated by binding to its nuclear receptors (TRα1 and TRβ, encoded by THRA and THRB, respectively) (1).
After binding to its nuclear receptor VDR, the complex 1,25-Dihydroxyvitamin D3 – VDR can influence bone metabolism indirectly by promoting intestinal absorption of calcium phosphate and directly by acting on osteoblasts and osteoclasts [ 16].
Once transported in the nucleus by an intracellular binding protein, calcitriol binds to its nuclear receptor which results in gene transcription and subsequent de novo protein synthesis.
Through binding to its cognate nuclear receptors with ligand-inducible property, T3 controls a broad range of gene expression in target tissues including liver.
The ligand-dependent molecular mechanism of SERMs is similar to that of 17β-estradiol and involves binding to its ligand-dependent nuclear ER.
TGFβ signaling pathways operate through distinct steps: ligand binding to its receptor, phosphorylation and nuclear accumulation of Smad2, and induction of target gene expression (ten Dijke and Hill, 2004; Massagué, 2012).
Tamoxifen is a selective OR modulator that blocks the binding of oestrogen to its nuclear receptor, is cytostatic in action (O'Regan and Jordan, 2002) and has been shown to reduce cell proliferation in IBC (Clarke et al, 1993) and in normal breast epithelium (Bernardes et al, 1999) as determined, using Ki67 nuclear antigen immunohistochemistry.
We established an assay to investigate whether there is reduced binding of progesterone receptor to its nuclear response element after, compared with before, labor onset.
Phosphorylation of cyclin D1 by GSK-3β (glycogen synthase kinase 3 beta) on the Thr-Pro site regulates turnover and localization of cyclin D1 by enhancing its binding to the nuclear transporter CRM1 and nuclear export, which leads to degradation of cyclin D1 in the nucleus [ 9, 10].
Calcitriol or 1,25-dihydroxycalciferol, the active form of vitamin D (VD), is known to regulate the gene transcription of Ca2+ transport factors TRPV6, CB, PMCA and NCX1 through its binding to the nuclear vitamin D receptor (VDR) in the enterocyte [ 3, 12- 14].
