Decrease of Ca(2+)-ATPase activity in human keratinocytes during calcium-induced differentiation.
Ca2+ regulates keratinocyte differentiation by increasing intracellular Ca2+ levels. Ca(2+)-ATPase in the Ca(2+)-induced differentiation of human keratinocytes was investigated by measuring Ca(2+)-ATPase mRNA, protein, and activity levels. Human keratinocytes were grown in Keratinocyte Growth Medium containing 0.03, 0.1, or 1.2 mM Ca2+ and assayed on days 2, 5, 7, 14, and 21. Ca(2+)-ATPase mRNA levels were found to be modestly increased in 5-, 7-, and 14-day cultured cells as compared with 2-day cultured cells, but levels fell below that of the 2-day cultured cells in the 21-day cultured cells. The Ca(2+)-ATPase mRNA levels were not affected by Ca2+ levels. A 135-kDa protein in human keratinocytes cross reacted with the monoclonal antibody against human erythrocyte Ca(2+)-ATPase. The level of this protein was decreased by Ca2+ and lost during differentiation, in parallel with the loss of enzymatic activity. Ca2+ influx of postconfluent 1.2 mM Ca(2+)-grown cells was higher than that of cells grown in lower Ca2+ concentrations. Ca2+ efflux from postconfluent cells grown in 0.03 mM Ca2+ was less than that from cells grown in stronger Ca2+ concentrations. These results suggest that the loss of the plasma membrane Ca(2+)-ATPase with time in culture contributes to the rise in intracellular Ca2+, thus promoting keratinocyte differentiation.
Cho
J K
JK
Department of Medicine, University of California, San Francisco, USA.
Bikle
D D
DD
D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002454:Cell Differentiation; D006801:Humans; D015603:Keratinocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D014158:Transcription, Genetic
D012333:RNA, Messenger; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium