Differential Regulation of Extracellular Signal-Related Kinase Phosphorylation by Vitamin D 3 Analogs

Vitamin D receptor is not essential for extracellular signal-related kinase phosphorylation by vitamin D(3) in human Caco-2/TC7 cells

Vitamin D(3) initiated rapid extracellular signal-related kinase (ERK) phosphorylation, but the contribution of vitamin D receptor (VDR) to this event is unclear. We investigated the use of RNA interference (RNAi) to knockdown VDR. RNAi downregulated VDR as well as its targeted gene expression, but vitamin D(3) dependent ERK phosphorylation remained. Thus VDR might not be involved in ERK phosphorylation by vitamin D(3).

A short practical approach to 24R,25-dihydroxyvitamin D3

A synthesis of the vitamin D3 metabolite 24R,25-dihydroxyvitamin D3 (1) by Lythgoe's Wittig-Horner approach is described. The key step of the synthesis is the stereocontrolled introduction of the 24-hydroxyl group by a palladium(0)-induced [3,3]-sigmatropic rearrangement on a 22R-allylic acetate (7).