Decrease of Ca2+-ATPase activity in human keratinocytes during calcium-induced differentiation

✍ Scribed by Jin-Kook Cho; Daniel D. Bikle

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 233 KB
• Volume: 172
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/(sici)1097-4652(199708)172:2<146::aid-jcp2>3.0.co;2-o

✦ Synopsis

Ca 2/ regulates keratinocyte differentiation by increasing intracellular Ca 2/ 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 Ca 2/ 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 2day cultured cells in the 21-day cultured cells. The Ca 2/ -ATPase mRNA levels were not affected by Ca 2/ 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 Ca 2/ and lost during differentiation, in parallel with the loss of enzymatic activity. Ca 2/ influx of postconfluent 1.2 mM Ca 2/ -grown cells was higher than that of cells grown in lower Ca 2/ concentrations. Ca 2/ efflux from postconfluent cells grown in 0.03 mM Ca 2/ was less than that from cells grown in stronger Ca 2/ concentrations. These results suggest that the loss of the plasma membrane Ca 2/ -ATPase with time in culture contributes to the rise in intracelluar Ca 2/ , thus promoting keratinocyte differentiation.