3.4. Vitamin D and Ca2þ signalling
Vitamin D may play an important role in maintaining intracellular
Ca2þ homoeostasis by regulating the expression of many of
the Ca2þ signalling components that act to reduce the level of Ca2þ
(Fig. 4) [88]. For example, Vitamin D can reduce the expression of
the L-type CaV1.2 and CaV1.3 channels [89] and can increase
expression of the PMCA and NCX1 that extrude Ca2þ and the calbindin
D-9k, calbindin D-28k and parvalbumen that buffer Ca2þ
[21,23,24,90]. In dendritic cells, administering vitamin D acts to
increase the expression of NCX that extrudes Ca2þ from the cell
[91]. Expression of the entry channels TRPV5 and TRPV6 is
increased and this has a specific role in promoting the transepithelial
flux of Ca2þ in the kidney and intestine