Induction and turnover of fructose 1,6-bisphosphatase in HL-60 leukemia cells by calcitriol.
Fructose 1,6-bisphosphatase mRNA and enzyme activity in HL-60 cells were rapidly and markedly induced by calcitriol (formerly known as 1 alpha,25-dihydroxyvitamin D3). The activity reached 70-80 times the basal level after 96 h. The enzyme activity in the cells incubated for 96 h with calcitriol decreased immediately after its withdrawal but after a 24-h incubation the activity in the cells continued to increase slightly and then decreased slowly. Calcitriol increased the enzyme activity dose-dependently with maximal stimulation at 10 nM and half-maximal at 2.1 nM. The rate of synthesis of fructose 1,6-bisphosphatase almost paralleled the increase in mRNA level during treatment with calcitriol. When calcitriol was removed from media after incubation for either 24 h or 96 h, fructose-1,6-bisphosphatase mRNA and fructose-1,6-bisphosphatase synthesis decreased rapidly to the basal level. The enzyme was only slightly degraded in the cells incubated with calcitriol for 24 h followed by the subsequent culture without calcitriol but it was degraded with a half-life estimated to be approximately 64 h in the same cells followed by culturing with calcitriol. In the cells incubated for 96 h, the same degradation rate (i.e. half-life approximately 64 h) was observed irrespective of the following culture with or without calcitriol. Calcitriol did not affect the degradation rate of total soluble proteins.
Mizunuma
H
H
Akita University College of Allied Medical Science, Japan.
Tashima
Y
Y
D001345:Autoradiography; D002117:Calcitriol / Q000494:pharmacology*; D002460:Cell Line; D004790:Enzyme Induction; D006597:Fructose-Bisphosphatase / Q000096:biosynthesis / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D015473:Leukemia, Promyelocytic, Acute; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D014316:Tritium; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D014316:Tritium; D006597:Fructose-Bisphosphatase; D002117:Calcitriol; D007930:Leucine