Calcium sensing receptor signalling in physiology and cancer.

The calcium sensing receptor (CaSR) is a class C G-protein-coupled receptor that is crucial for the feedback regulation of extracellular free ionised calcium homeostasis. While extracellular calcium (Ca(2+)o) is considered the primary physiological ligand, the CaSR is activated physiologically by a plethora of molecules including polyamines and l-amino acids. Activation of the CaSR by different ligands has the ability to stabilise unique conformations of the receptor, which may lead to preferential coupling of different G proteins; a phenomenon termed 'ligand-biased signalling'.

Epigenetic regulation of the 1,25-dihydroxyvitamin D3 24-hydroxylase (CYP24A1) in colon cancer cells.

Calcitriol is the hormonally active form of vitamin D and has anti-proliferative and pro-apoptotic effects. Calcitriol and its precursor calcidiol (25(OH)D3) are degraded by the 1,25-dihydroxyvitamin D3 24-hydroxylase (CYP24A1). This enzyme is overexpressed in colorectal tumors, however, the mechanisms of this overexpression remain to be elucidated.