Vitamin D3 upregulates plasma membrane Ca2+-ATPase expression and potentiates apico-basal Ca2+ flux in MDCK cells.
Plasma membrane Ca2+-ATPases (PMCAs) are a ubiquitous system for the expulsion of Ca2+ from eukaryotic cells. In tight monolayers of polarized Madin-Darby canine kidney (MDCK) cells representing a distal kidney tubule model, PMCAs are responsible for about one-third of the vectorial Ca2+ transport under resting conditions, with the remainder being provided by the Na+/Ca2+ exchanger. Vitamin D3 (VitD) is known to increase PMCA expression and activity in Ca2+-transporting tissues such as the intestine, as well as in osteoblasts and Madin-Darby bovine kidney epithelial cells. We found that VitD upregulated the expression of the PMCAs (mainly PMCA4b) in MDCK cell lysates at the RNA and protein level in a time- and dose-dependent manner. Interestingly, VitD caused a decrease of the PMCAs in the apical plasma membrane fraction and a concomitant increase of the pumps in the basolateral membrane. Functional studies demonstrated that transcellular 45Ca2+ flux from the apical-to-basolateral compartment was significantly enhanced by VitD. These findings demonstrate that VitD is a positive regulator of the PMCAs in MDCK epithelial cells. The correlation of decreased apical/increased basolateral expression of the PMCAs with an increase in transcellular Ca2+ flux from the apical (urine) toward the basolateral (blood) compartment indicates the physiological relevance of VitD function in kidney tubular Ca2+ reabsorption.
Kip
Sertac N
SN
Department of Biochemistry, Mayo Clinic, Rochester, MN 55905, USA.
Strehler
Emanuel E
EE
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000235:genetics* / Q000378:metabolism*; D027682:Cation Transport Proteins; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D016764:Cell Polarity / Q000502:physiology; D002762:Cholecalciferol / Q000494:pharmacology*; D007686:Kidney Tubules, Distal / Q000166:cytology / Q000201:enzymology*; D053499:Plasma Membrane Calcium-Transporting ATPases; D012333:RNA, Messenger / Q000032:analysis; D015854:Up-Regulation / Q000187:drug effects
D027682:Cation Transport Proteins; D012333:RNA, Messenger; D002762:Cholecalciferol; D053499:Plasma Membrane Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium